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Nº de abstracts = 72 Modificado em 16 Março 2012
Attenuated relationship between cardiac output and oxygen uptake during high-intensity exercise.Trinity JD, Lee JF, Pahnke MD, Beck KC, Coyle EF.: Acta Physiologica (Oxford, England), Março 2012, 204(3):362-70. Aim: Recent findings have challenged the belief that the cardiac output (CO) and oxygen consumption (VO2) ) relationship is linear from rest to maximal exercise. The purpose of this study was to determine the CO and stroke volume (SV) response to a range of exercise intensities, 40-100% of VO2max), during cycling. Methods: Ten well-trained cyclists performed a series of discontinuous exercise bouts to determine the CO and SV vs. VO2 responses. Results: The rate of increase in CO, relative to VO2, during exercise from 40 to 70% of VO2max) was 4.4 ± 1.4 L L-1. During exercise at 70-100% of VO2max) , the rate of increase in CO was reduced to 2.1 ± 0.9 L L(-1) (P = 0.01). Stroke volume during exercise at 80-100% of VO2max) was reduced by 7% when compared to exercise at 50-70% of VO2max) (134 ± 5 vs. 143 ± 5 ml per beat, P = 0.02). Whole body arterial-venous O2 difference increased significantly as intensity increased. Conclusion: The observation that the rate of increase in CO is reduced as exercise intensity increases suggests that cardiovascular performance displays signs of compromised function before maximal VO2 is reached.
A new VO2max protocol allowing self-pacing in maximal incremental exercise.Mauger AR, Sculthorpe N.: British Journal of Sports Medicine, Jan 2012, 46(1):59-63. Introduction The traditional maximal oxygen uptake (VO2max)) protocol has received criticism for being an unnatural form of exercise, lacking ecological validity and producing different VO2max) responses depending on protocol duration and work rate increments. Purpose The purpose of this investigation was to design and test a new VO2max) protocol allowing subjects to self-pace their work rate while maintaining an incremental test structure. Methods 16 untrained subjects completed a self-paced VO2max) protocol (SPV) and a traditional VO2max) test in a counter-balanced, crossover design. The SPV used incremental 'clamps' of ratings of perceived exertion (RPE) over 5 × 2-min stages (10-min duration) while allowing subjects to vary their power output (PO) according to the required RPE. Results Subjects achieved significantly higher (p < 0.05) VO2max) values (40 ± 10 ml/kg/min vs 37 ± 8 ml/kg/min) and peak POs (273 ± 58 W vs 238 ± 55 W) in the SPV. Higher VO2max) values were observed in the SPV even when a plateau (VO2-time slope <0.05 l/min) occurred in the traditional test. No differences were found between any other measured physiological variable (minute ventilation, heart rate and respiratory exchange ratio). Conclusions As SPV is a closed-loop test (10-min duration) that allows subjects to self-pace their work rate, it disregards the need for experimenters to estimate starting work rates, stage lengths and increments in order to bring about volitional exhaustion in 8-10 min. The observation that the SPV may also elicit higher VO2max) values than a traditional test warrants further research in this area and its consideration as standard measure to elicit VO2max).
Allergic and non-allergic rhinitis in swimmers: clinical and cytological aspects.Gelardi M, Ventura MT, Fiorella R, Fiorella ML, Russo C, Candreva T, Carretta A, Passalacqua G.: British Journal of Sports Medicine, Jan 2012, 46(1):54-8. Background Rhinitis, either allergic or non-allergic, is frequent in athletes, particularly in swimmers. In this latter case, exposure to chlorine in swimming pools seems to play a relevant role, since it can exacerbate a pre-existing allergic rhinitis (AR) or produce a non-specific irritation. The aim of this study was to detail the clinical and cytological characteristics of rhinitis in swimmers, and to assess the possible role of chlorine-induced symptoms. Methods Elite swimmers with rhinitis symptoms underwent a complete diagnostic work-up, including allergy testing, nasal cytology and anterior rhinomanometry. Those evaluations were repeated after 1 month of use of a nasal clip during swimming. A matched group of asymptomatic swimmers was also studied. A total of 74 swimmers (54 symptomatic and 20 controls), with an age range of 9-21 years, were studied. In the control group, only mild and non-specific findings were observed, and only two had a positive skin test. Results In the symptomatic group, 24 (44%) had AR, and 19 (35%) had a predominant neutrophilic inflammation. The use of a nose clip reduced cellular infiltration and nasal resistances only in the subjects with neutrophilic rhinitis, whereas a clinical improvement was seen also in AR. Conclusion A neutrophilic rhinitis occurs in a large proportion of swimmers. This seems to be irritative in its nature and can be prevented by avoiding the direct contact with chlorinated water.
The mechanisms of muscle hypertrophy and their application to resistance training.Schoenfeld BJ.: Journal of strength and conditioning research / National Strength & Conditioning Association 201010 24(10):2857-72. Global Fitness Services, Scarsdale, New York, USA. The quest to increase lean body mass is widely pursued by those who lift weights. Research is lacking, however, as to the best approach for maximizing exercise-induced muscle growth. Bodybuilders generally train with moderate loads and fairly short rest intervals that induce high amounts of metabolic stress. Powerlifters, on the other hand, routinely train with high-intensity loads and lengthy rest periods between sets. Although both groups are known to display impressive muscularity, it is not clear which method is superior for hypertrophic gains. It has been shown that many factors mediate the hypertrophic process and that mechanical tension, muscle damage, and metabolic stress all can play a role in exercise-induced muscle growth. Therefore, the purpose of this paper is twofold: (a) to extensively review the literature as to the mechanisms of muscle hypertrophy and their application to exercise training and (b) to draw conclusions from the research as to the optimal protocol for maximizing muscle growth.
Oxidative stress and antioxidant defense mechanisms linked to exercise during cardiopulmonary and metabolic disorders.Fisher-Wellman K, Bell HK, Bloomer RJ.: Oxidative medicine and cellular longevity 200901 2(1):43-51. Cardiorespiratory/Metabolic Laboratory; The University of Memphis; Memphis, Tennessee USA. Oxidative stress has been implicated in the pathophysiology of multiple human diseases, in addition to the aging process. Although various stimuli exist, acute exercise is known to induce a transient increase in reactive oxygen and nitrogen species (RONS), evident by several reports of increased oxidative damage following acute bouts of aerobic and anaerobic exercise. Although the results are somewhat mixed and appear disease dependent, individuals with chronic disease experience an exacerbation in oxidative stress following acute exercise when compared to healthy individuals. However, this increased oxidant stress may serve as a necessary "signal" for the upregulation in antioxidant defenses, thereby providing protection against subsequent exposure to prooxidant environments within susceptible individuals. Here we present studies related to both acute exercise-induced oxidative stress in those with disease, in addition to studies focused on adaptations resulting from increased RONS exposure associated with chronic exercise training in persons with disease.
Attenuated RPE and leg pain in response to short-term high-intensity interval training. Astorino TA, Allen RP, Roberson DW, Jurancich M, Lewis R, McCarthy K20120101
105(2):402-7 Department of Kinesiology, California State University, San Marcos, 333. S. Twin Oaks Valley Road, MH 352, San Marcos, CA 92096-0001, United States. This study examined the effect of 6days of high intensity interval training (HIT) on rating of perceived exertion (RPE) and leg pain. Eleven men (age and VO(2)max=25.3±5.5year and 45.6±mL/kg/min) and 9 women (age and VO(2)max=25.2±3.1year and 41.1±6.1mL/kg/min) with similar activity level and VO(2)max underwent HIT consisting of repeated Wingate tests separated by 5min recovery over a 2-3 week period. Five men and four women served as controls and did not perform HIT. Four minutes after each bout across all days of training, RPE and leg pain were recorded using categorical scales. Repeated measure ANOVA was used to assess differences in RPE and leg pain in response to acute bouts and days of HIT. Data revealed that RPE and pain increased (p<0.05) after bout 1 to after bout 4. Compared to day 1 (6.3±1.9), RPE after bout 4 (5.0±1.4) decreased (p=0.001) in response to 6d of HIT. Training significantly reduced (p<0.05) leg pain, as pain declined from day 1 (6.20±2.29) of HIT versus day 6 (5.20±2.04). Data show that RPE and leg pain are significantly attenuated by 6d of HIT, which is likely due to the physiological adaptations accrued in response to this modality of training.
Association of serum bicarbonate levels with gait speed and quadriceps strength in older adults. Abramowitz MK, Hostetter TH, Melamed ML.:201107 58(1):29-38. BACKGROUND: Metabolic acidosis is associated with skeletal muscle proteolysis, and alkali supplementation has shown improvements in lean body mass and urinary nitrogen wasting in several studies. However, the association of acidosis with functional outcomes has not been examined on a population-based level. STUDY DESIGN: Cross-sectional study. SETTING & PARTICIPANTS: 2,675 nationally representative adults 50 years or older in the National Health and Nutrition Examination Survey 1999-2002. FACTOR: Serum bicarbonate level. OUTCOMES: Low gait speed and low peak torque were defined as being in the lowest sex-specific quartile of gait speed and peak torque, respectively. MEASUREMENTS: Serum bicarbonate was measured in all participants. Gait speed was determined from a 20-foot timed walk. Peak torque was calculated using peak isokinetic knee extensor force. RESULTS: Serum bicarbonate level <23 mEq/L was present in 22.7% of the cohort. Compared with participants with bicarbonate levels =23 mEq/L, those with bicarbonate levels <23 mEq/L had higher body mass index and serum albumin levels; were more likely to have low socioeconomic status, a diagnosis of diabetes mellitus, or glomerular filtration rate <60 mL/min/1.73 m(2); and were less likely to use diuretics. Serum bicarbonate level <23 mEq/L compared with =23 mEq/L was associated with low gait speed (OR, 1.43; 95% CI, 1.04-1.95) and low peak torque (OR, 1.36; 95% CI, 1.07-1.74) after multivariable adjustment. The association with low peak torque was modified by race/ethnicity in women, but not men (ORs, 1.52 [95% CI, 1.08-2.13] for men, 2.33 [95% CI, 1.23-4.44] for nonwhite women, and 0.93 [95% CI, 0.47-1.82] for white women). LIMITATIONS: Cross-sectional study using a single bicarbonate measurement. CONCLUSIONS: Lower serum bicarbonate levels are associated with slower gait speed and decreased quadriceps strength in older adults. Further studies should examine the effect of alkali therapy on functional outcomes.
Environmental temperature and glycogen resynthesis.Naperalsky M, Ruby B, Slivka D.: International Journal of Sports Medicine, 2010, 31(8):561-6. University of Montana, Montana Center For Work Physiology and Exercise Metabolism, Missoula, United States. This study investigated the effects of hot (H) and room temperature (RT) recovery environments on glycogen resynthesis. Nine male participants completed two trials, cycling for 1 h in a temperature-controlled chamber (32.6 degrees C), followed by 4 h of recovery at 32.6 degrees C (H) or 22.2 degrees C (RT). Rectal temperature was continuously recorded. A carbohydrate beverage (1.8 g/kg bodyweight) was supplied at 0 and 2 h post-exercise. Muscle biopsies were taken immediately, 2 h, and 4 h post-exercise for glycogen analysis. Blood samples were taken at 30, 60, 120, 150, 180, and 240 min into recovery for glucose and insulin analysis. Expired gas was collected at 105 min and 225 min into recovery to calculate whole body carbohydrate oxidation. Average core temperature, whole body carbohydrate oxidation, and serum glucose at 120, 150, 180 and 240 min was higher in H compared to RT (p<0.05). Muscle glycogen was higher in RT vs. H at 4 h (105+/-28 vs. 88+/-24 mmolxkg (-1) wet weight, respectively; p<0.05), but no different at 0 and 2 h. There was no difference in serum insulin. These data indicate the importance of minimizing the exposure to heat after exercise to improve recovery, specifically to improve glycogen resynthesis.
Fitness profiling in handball: physical and physiological characteristics of elite playersSporis G, Vuleta D, Vuleta D, Milanović D.: Collegium Antropologicum, 2010, 34(3):1009-14. Faculty of Kinesiology, Zagreb University, Zagreb, Croatia. The purpose of this study was to describe the structural and functional characteristics of elite Croatian handball players and to evaluate whether the players in different positional roles have different physical and physiological profiles. According to the positional roles, players were categorized as goalkeepers (n = 13), wing players (n = 26), backcourt players (n = 28) and pivot players (n = 25). The goalkeepers were older (p < 0.01), and the pivot players were more experienced (p < 0.01) than the backcourt players. The wings were the shortest players in the team. The pivots were tallest and heavier than the backcourt and wing players (p < 0.01), whereas the backcourt players were tallest then wings (p < 0.01). Goalkeepers had more body fat than the backcourt and wing players (p < 0.01). The backcourt players had a lower percentage of body fat. The backcourt players were the quickest players in the team when looking at values of maximal running speed on a treadmill. The Goalkeepers were the slowest players in the team (p < 0.01). The best average results concerning maximal heart rate were detected among the backcourt players. There were no statistically significant differences between the players'positions when measuring blood lactate and maximal heart rate. A strong negative correlation was found between body fat and maximal running speed (r = -0.68, p < 0.01). Coaches are able to use this information to determine which type of profile is needed for a specific position. Experienced coaches can used this information in the process of designing a training program to maximize the fitness development of handball players, with one purpose only, to achieve success in handball.
Endurance exercise induces mRNA expression of oxidative enzymes in human skeletal muscle late in recoveryLeick L, Plomgaard P, Grønløkke L, Al-Abaiji F, Wojtaszewski JF, Pilegaard H.: Scandinavian journal of medicine & science in sports. 2010, 20(4):593-9. Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark. Exercise-induced adaptations in skeletal muscle oxidative enzymes are suggested to result from the cumulative effects of transient changes in gene expression after each single exercise session. However, for several oxidative enzymes, no changes in mRNA expression are detected up to 8 h after exercise. To test the hypothesis that mRNA expression of many oxidative enzymes is up-regulated late in recovery (10-24 h) after exercise, male subjects (n=8) performed a 90-min cycling exercise (70% VO(2-max)), with muscle biopsies obtained before exercise (pre), and after 10, 18 and 24 h of recovery. The mRNA expression of carnitine-palmitoyltransferase (CPT)I, CD36, 3-hydroxyacyl-CoA-dehydrogenase (HAD), cytochrome (Cyt)c, aminolevulinate-delta-synthase (ALAS)1 and GLUT4 was 100-200% higher at 10-24 h of recovery from exercise than in a control trial. Exercise induced a 100-300% increase in peroxisome proliferator-activated receptor gamma co-activator (PGC)-1alpha, citrate synthase (CS), CPTI, CD36, HAD and ALAS1 mRNA contents at 10-24 h of recovery relative to before exercise. No protein changes were detected in Cytc, ALAS1 or GLUT4. This shows that mRNA expression of several training-responsive oxidative enzymes is up-regulated in human skeletal muscle at 10-24 h of recovery, supporting that exercise-induced adaptations of these oxidative enzymes can be the result of the cumulative effects of transient changes in mRNA expression.
The impact of moderate-altitude staging on pulmonary arterial hemodynamics after ascent to high altitudeBaggish AL, Fulco CS, Muza S, Rock PB, Beidleman B, Cymerman A, Yared K, Fagenholz P, Systrom D, Wood MJ, Weyman AE, Picard MH, Harris NS.: High altitude medicine & biology, 2010, 11(2):139-45. Massachusetts General Hospital, Boston, 02114, USA. Staged ascent (SA), temporary residence at moderate altitude en route to high altitude, reduces the incidence and severity of noncardiopulmonary altitude illness such as acute mountain sickness. To date, the impact of SA on pulmonary arterial pressure (PAP) is unknown. We tested the hypothesis that SA would attenuate the PAP increase that occurs during rapid, direct ascent (DA). Transthoracic echocardiography was used to estimate mean PAP in 10 healthy males at sea level (SL, P(B) approximately 760 torr), after DA to simulated high altitude (hypobaric chamber, P(B) approximately 460 torr), and at 2 times points (90 min and 4 days) during exposure to terrestrial high altitude (P(B) approximately 460 torr) after SA (7 days, moderate altitude, P(B) approximately 548 torr). Alveolar oxygen pressure (Pao(2)) and arterial oxygenation saturation (Sao(2)) were measured at each time point. Compared to mean PAP at SL (mean +/- SD, 14 +/- 3 mmHg), mean PAP increased after DA to 37 +/- 8 mmHg (Delta = 24 +/- 10 mmHg, p < 0.001) and was negatively correlated with both Pao(2) (r(2) = 0.57, p = 0.011) and Sao(2) (r(2) = 0.64, p = 0.005). In comparison, estimated mean PAP after SA increased to only 25 +/- 4 mmHg (Delta = 11 +/- 6 mmHg, p < 0.001), remained unchanged after 4 days of high altitude residence (24 +/- 5 mmHg, p = not significant, or NS), and did not correlate with either parameter of oxygenation. SA significantly attenuated the PAP increase associated with continuous direct ascent to high altitude and appeared to uncouple PAP from both alveolar hypoxia and arterial hypoxemia.
The Silver Hut expedition, 1960-1961Milledge JS.: High altitude medicine & biology, 2010, 11(2):93-101. University College London, Institute of Child Health, UK. The 1960-1961 Himalayan Scientific and Mountaineering Expedition, commonly known as the Silver Hut Expedition, was a unique project to study the physiology of acclimatization in human lowlander subjects at extreme altitude over a prolonged period and also to make an attempt on Makalu, an 8470-m peak. The leader was Sir Edmund Hillary, and Dr. Griffith Pugh was the scientific leader. Studies were conducted at a Base Camp in the Everest region of Nepal at 4500 m and at the Silver Hut at 5800 m on the Mingbo Glacier. Simpler physiology was continued on Makalu, in camps at 6300 and 7400 m. The expedition left Kathmandu at the end of the monsoon in 1960 and spent the autumn setting up the Base Camp and the Silver Hut. Some members also spent time making a study of the evidence for the existence of the Yeti. The winter was spent on physiological studies at Base Camp and in the Silver Hut, and the nearby peak of Ama Dablam was climbed. In the spring the expedition moved over to Makalu and made an unsuccessful attempt to climb it without supplementary oxygen. The 9-month expedition ended at the start of the 1961 monsoon. An ambitious program of studies was successfully completed. It was a very happy and, scientifically, a successful expedition. Many of the findings were not repeated for many years, and none has been refuted. On the mountaineering side, we were unsuccessful on Makalu owing to a combination of weather and illness, but the ascent of Ama Dablam was considerable compensation.
Caudwell xtreme Everest expedition.Grocott MP, Martin DS, Wilson MH, Mitchell K, Dhillon S, Mythen MG, Montgomery HE, Levett DZ.: High altitude medicine & biology, 2010, 11(2):133-7. The Caudwell Xtreme Everest (CXE) expedition involved the detailed study of 222 subjects ascending to 5300 m or higher during the first half of 2007. Following baseline measurements at sea level, 198 trekker-subjects trekked to Everest Base Camp (EBC) following an identical ascent profile. An additional group of 24 investigator-subjects followed a similar ascent to EBC and remained there for the duration of the expedition, with a subgroup of 14 collecting data higher on Everest. This article focuses on published data obtained by the investigator-subjects at extreme altitude (>5500 m). Unique measurements of peak oxygen consumption, middle cerebral artery diameter and blood velocity, and microcirculatory blood flow were made on the South Col (7950 m). Unique arterial blood gas values were obtained from 4 subjects at 8400 m during descent from the summit of Everest. Arterial blood gas and microcirculatory blood flow data are discussed in detail.
Operation Everest IIWagner PD.: High altitude medicine & biology, 2010, 11(2):111-9. Department of Medicine, University of California, San Diego, La Jolla, 92093-0623, USA. In October 1985, 25 years ago, 8 subjects and 27 investigators met at the United States Army Research Institute for Environmental Medicine (USARIEM) altitude chambers in Natick, Massachusetts, to study human responses to a simulated 40-day ascent of Mt. Everest, termed Operation Everest II (OE II). Led by Charlie Houston, John Sutton, and Allen Cymerman, these investigators conducted a large number of investigations across several organ systems as the subjects were gradually decompressed over 40 days to the Everest summit equivalent. There the subjects reached a V(O)(2)max of 15.3 mL/kg/min (28% of initial sea-level values) at 100 W and arterial P(O(2)) and P(CO(2)) of approximately 28 and approximately 10 mm Hg, respectively. Cardiac function resisted hypoxia, but the lungs could not: ventilation-perfusion inequality and O(2) diffusion limitation reduced arterial oxygenation considerably. Pulmonary vascular resistance was increased, was not reversible after short-term hyperoxia, but was reduced during exercise. Skeletal muscle atrophy occurred, but muscle structure and function were otherwise remarkably unaffected. Neurological deficits (cognition and memory) persisted after return to sea level, more so in those with high hypoxic ventilatory responsiveness, with motor function essentially spared. Nine percent body weight loss (despite an unrestricted diet) was mainly (67%) from muscle and exceeded the 2% predicted from energy intake-expenditure balance. Some immunological and lipid metabolic changes occurred, of uncertain mechanism or significance. OE II was unique in the diversity and complexity of studies carried out on a single, courageous cohort of subjects. These studies could never have been carried out in the field, and thus complement studies such as the American Medical Research Expedition to Everest (AMREE) that, although more limited in scope, serve as benchmarks and reality checks for chamber studies like OE II.
Operation Everest III: COMEX '97Richalet JP.: High altitude medicine & biology, 2010, 11(2):121-32. Université Paris, Bobigny, France. Eight male volunteers, aged 23 to 37, were selected to participate in a simulated ascent to 8848 m in a hypobaric chamber. They were first preacclimatized in the Observatoire Vallot (4350 m) before entering the chamber. The chamber was progressively decompressed down to 253 mmHg barometric pressure, with a recovery period of 3 days at 5000 m from days 20 to 22. They spent a total of 31 days in the chamber. Seventeen protocols were organized by 14 European teams to explore the limiting factors of physical and psychological performance and the physiological and pathological changes in various systems (cardiac function, control of ventilation, autoregulation of cerebral blood flow, energy balance and body composition, muscle performance, erythropoiesis, and cognitive functions). All subjects reached 8000 m, and 7 of them reached the simulated altitude of 8848 m. Three subjects complained of transient neurological symptoms, which resolved rapidly with reoxygenation. At 8848 m (n = 5), Pa(O(2)) was 30.6 +/- 1.4 mmHg, Pc(O(2)) was 11.9 +/- 1.4 mmHg, and pH was 7.58 +/- 0.02 (arterialized capillary blood). V(O(2))max decreased by 59% at 7000 m and increased by 9% at 6000 m after plasma expansion, suggesting a role of altitude-induced plasma contraction in the reduction in V(O(2))max. Cardiac contractility was normal, but relaxation was slightly impaired. Autoregulation of cerebral blood flow was impaired at 8000 m. Negative energy balance was essentially caused by a decrease in appetite. Increased membrane lipid peroxidation could explain alterations in muscle or cognitive function. The subjects reached the "summit" in better physiological conditions than would have been possible in the mountains, probably because acclimatization and other environmental factors such as cold and nutrition were controlled.
Fatal accidents among elite mountaineers: A historical perspective from the European Alps.Weinbruch S, Nordby KC.: High altitude medicine & biology, 2010, 11(2):147-51. Institute of Applied Geosciences, Technical University Darmstadt, Germany. The lifetime risk of a fatal mountain accident among elite European alpine mountaineers and its time trends are determined by studying a fixed cohort of 390 elite mountaineers listed in the Encyclopaedia of the Alps (Hiebler, 1977). At publication of the encyclopaedia, 158 individuals were still living and were followed up until the end of 2008. The crude lifetime risk of a fatal accident for elite mountaineers is 0.203 [95% confidence interval (CI), 0.165 to 0.246). The difference in mortality between male (0.207; 95% CI: 0.168 to 0.251) and female mountaineers (0.118; 95% CI: 0.033 to 0.343) is not statistically significant. No fatal accidents occurred among elite mountaineers born before 1820. For the birth cohort from 1820 to 1949, the lifetime risk of a fatal accident (male mountaineers only) increased with time from 0.069 (95% CI, 0.019 to 0.220) to 0.375 (95% CI, 0.212 to 0.573). For all time strata, the highest risk of a fatal mountain accident was observed at an age of 30 to 39 yr. The high mortality among elite mountaineers clearly demonstrates that the limits of human performance are reached by these activities. The high risks should be communicated and should motivate risk-reduction efforts for this highly exposed subgroup of mountaineers.
Altitude preexposure recommendations for inducing acclimatization.Muza SR, Beidleman BA, Fulco CS.: High altitude medicine & biology, 2010, 11(2):87-92. U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760-5007, USA. For many low-altitude (2400 m) altitudes without having the time to develop an adequate degree of altitude acclimatization. Prior to departing on these trips, low-altitude residents can induce some degree of altitude acclimatization by ascending to moderate (>1500 m) or high altitudes during either continuous or intermittent altitude preexposures. Generally, the degree of altitude acclimatization developed is proportional to the altitude attained and the duration of exposure. The available evidence suggests that continuous residence at 2200 m or higher for 1 to 2 days or daily 1.5- to 4-h exposures to >4000 m induce ventilatory acclimatization. Six days at 2200 m substantially decreases acute mountain sickness (AMS) and improves work performance after rapid ascent to 4300 m. There is evidence that 5 or more days above 3000 m within the last 2 months will significantly decrease AMS during a subsequent rapid ascent to 4500 m. Exercise training during the altitude preexposures may augment improvement in physical performance. The persistence of altitude acclimatization after return to low altitude appears to be proportional to the degree of acclimatization developed. The subsequent ascent to high altitude should be scheduled as soon as possible after the last altitude preexposure.
American medical research expedition to Everest.West JB.: High altitude medicine & biology, 2010, 11(2):103-10. Department of Medicine, University of California San Diego, La Jolla, 92093-0623, USA. The primary objective of the American Medical Research Expedition to Everest was to obtain information on human physiology at the highest possible altitude, including the Everest summit. An important data point was the barometric pressure on the summit, because this determines the inspired P(O(2)). The first measurement ever taken was 253.0 mmHg. Because modeling studies had shown that extreme hyperventilation was essential to reach these great altitudes, 34 alveolar gas samples were collected above an altitude of 8000 m, including 4 on the summit. These showed that hyperventilation reduced the alveolar P(CO(2)) to between 7 and 8 mmHg in one climber. An important finding was that alveolar P(O(2)) was defended at a value of about 35 mmHg by the increasing hyperventilation as the climbers ascended higher. Venous blood samples collected on two summiters gave a mean base excess of -7.2 meq.L(-1). Using the alveolar P(CO(2)) value, this gave an arterial pH of over 7.7, indicating an extreme degree of respiratory alkalosis. While climbing at an altitude of 8300 m, one summiter showed a respiratory frequency of 86 breaths.min(-1) and tidal volume of 1.26 L, indicating very rapid shallow breathing. Maximal oxygen consumption for the summit was derived by having well-acclimatized subjects exercise maximally at an altitude of 6300 m while breathing 14% oxygen. The V(O(2)) was just over 1 L.min(-1), which is sufficient to explain how exceptional humans can reach the summit without supplementary oxygen. In addition to the measurements at altitudes over 8000 m, data were obtained at two camps at 5400- and 6300-m altitude. These gave information on the control of ventilation, periodic breathing, blood physiology, cerebral function, and metabolism.
A longitudinal assessment of running economy and tendon properties in long-distance runners.Kubo K, Tabata T, Ikebukuro T, Igarashi K, Tsunoda N .: Journal of strength and conditioning research / National Strength & Conditioning Association, 2010, 24(7):1724-31. Department of Life Science, University of Tokyo, Meguro, Tokyo, Japan. The aim of this study was to investigate longitudinal changes in tendon properties and running economy of long-distance runners (LDRs) in the preparatory periods of track season (TS) and road season (RS). Eleven well-trained LDRs and 6 untrained subjects participated in the present study. In each period, muscle strength, neural activation level, and tendon elongation for both knee extensors and plantar flexors, jump performances, and oxygen consumption during submaximal running velocities were measured. No significant differences observed in any measured variables between the 2 seasons for untrained subjects. For LDRs, the total running distance during 1 month preceding RS (832 +/- 95 km) was significantly longer than that during 1 month preceding TS (718 +/- 80 km). No significant differences in the muscle strength, neural activation level, and jump performances were found between TS and RS. The stiffness of tendon structures in RS was significantly lower than those in TS for both knee extensors (-14.4%, p = 0.023) and plantar flexors (-16.6%, p = 0.040). At 3 running velocities, the oxygen consumptions in RS were significantly lower than those in TS. These results suggested that the lower oxygen consumption during submaximal running velocities observed in the preparatory period of RS may be attributable to the more compliant tendon structures but not in the neuromuscular characteristics.
Physiological demands of team-handball referees during games.da Silva JF, Castagna C, Carminatti LJ, Foza V, Guglielmo LG, de Oliveira FR.: Journal of strength and conditioning research / National Strength & Conditioning Association, 2010, 24(7):1960-2. Physical Effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianópolis, Brazil. The objective of the present study was to examine the aerobic fitness and the physiological demands during competitive games in elite handball referees. Sixteen referees (age: 34.9 +/- 3.4 years, body mass: 77.4 +/- 10.6 kg, height: 173.5 +/- 7.5 cm, percent fat: 22.3 +/- 6.6%) of national and international levels (14 men and 2 women) were submitted to a multistage fitness test, to determine peak velocity (PV) and maximal heart rate (HR). After 48 hours, referees performed a submaximal intermittent shuttle-running test (3 minutes at 75 and 90% PV with 1-minute recovery), to determine speeds and HR at selected blood-lactate concentrations (2.0 and 4.0 mmol.L(-1)). Game intensities were arbitrarily established as follows: HR4mmol (severe). Eight referees (2 per game) were monitored in 4 national level games. The mean VO(2)max of the referees was 48.5 +/- 6.1 ml.kg(-1).min(-1). Maximal HR, HR2mmol, and HR4mmol were 193 +/- 10, 154 +/- 13, and 167 +/- 10 b.min, respectively. The percent time spent in the moderate intensity domain was predominant (moderate 96.4%, heavy 2.3%, and severe 1.3% of total time, p < 0.05). These findings indicate that handball refereeing is of moderate intensity. In light of this study, results aerobic fitness does not seem to be a limiting factor in handball refereeing.
Physical and physiological attributes of female volleyball players--a reviewLidor R, Ziv G.: Journal of strength and conditioning research / National Strength & Conditioning Association, 2010, 24(7):1963-73. The Zinman College of Physical Education and Sport Sciences, Wingate Institute. The main objective of this article was to review a series of studies (n = 31) on physical attributes, physiological attributes, and on-court performances of female volleyball players. Empirical and practical knowledge emerging from studies on training-related issues in volleyball, such as body mass, fat-free mass, aerobic profile, strength, and agility and speed, should be integrated and applied when planning annual training programs for volleyball players. Based on our review, it was found that (a) players of a higher skill level are taller, somewhat heavier, and have higher vertical jump values than players of a lower level; (b) the aerobic profile of female volleyball players is similar to that of female basketball players; (c) ballistic resistance training can increase vertical jump values in female volleyball players; and (d) preseason conditioning should be conducted to prevent fatigue and reduced performance at the beginning of the season. Among the research concerns discussed in the article are that there is a lack data for on-court performance and time-motion analysis in female volleyball players and that more experimental/manipulative studies are needed to examine the effectiveness of different training programs on physiological attributes of female volleyball players. Two practical implications are suggested for volleyball and strength and conditioning coaches: (a) functional and nonfunctional overreaching should be carefully monitored when planning strength and conditioning programs, and (b) volleyball programs should include ballistic-type training.
Using molecular classification to predict gains in maximal aerobic capacity following endurance exercise training in humans.Timmons JA, Knudsen S, Rankinen T, Koch LG, Sarzynski M, Jensen T, Keller P, Scheele C, Vollaard NB, Nielsen S, Akerström T, MacDougald OA, Jansson E, Greenhaff PL, Tarnopolsky MA, van Loon LJ, Pedersen BK, Sundberg CJ, Wahlestedt C, Britton SL, Bouchard C.: Journal of applied physiology (Bethesda, Md. : 1985), 2010-06 108(6):1487-96. Panum Institutet and Center for Healthy Ageing, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark. A low maximal oxygen consumption (VO2max) is a strong risk factor for premature mortality. Supervised endurance exercise training increases VO2max with a very wide range of effectiveness in humans. Discovering the DNA variants that contribute to this heterogeneity typically requires substantial sample sizes. In the present study, we first use RNA expression profiling to produce a molecular classifier that predicts VO2max training response. We then hypothesized that the classifier genes would harbor DNA variants that contributed to the heterogeneous VO2max response. Two independent preintervention RNA expression data sets were generated (n=41 gene chips) from subjects that underwent supervised endurance training: one identified and the second blindly validated an RNA expression signature that predicted change in VO2max ("predictor" genes). The HERITAGE Family Study (n=473) was used for genotyping. We discovered a 29-RNA signature that predicted VO2max training response on a continuous scale; these genes contained approximately 6 new single-nucleotide polymorphisms associated with gains in VO2max in the HERITAGE Family Study. Three of four novel candidate genes from the HERITAGE Family Study were confirmed as RNA predictor genes (i.e., "reciprocal" RNA validation of a quantitative trait locus genotype), enhancing the performance of the 29-RNA-based predictor. Notably, RNA abundance for the predictor genes was unchanged by exercise training, supporting the idea that expression was preset by genetic variation. Regression analysis yielded a model where 11 single-nucleotide polymorphisms explained 23% of the variance in gains in VO2max, corresponding to approximately 50% of the estimated genetic variance for VO2max. In conclusion, combining RNA profiling with single-gene DNA marker association analysis yields a strongly validated molecular predictor with meaningful explanatory power. VO2max responses to endurance training can be predicted by measuring a approximately 30-gene RNA expression signature in muscle prior to training. The general approach taken could accelerate the discovery of genetic biomarkers, sufficiently discrete for diagnostic purposes, for a range of physiological and pharmacological phenotypes in humans.
Myocellular basis for tapering in competitive distance runners.Luden N, Hayes E, Galpin A, Minchev K, Jemiolo B, Raue U, Trappe TA, Harber MP, Bowers T, Trappe S.: Journal of applied physiology (Bethesda, Md. : 1985), 2010-06 108(6):1501-9. Human Performance Laboratory, Ball State University, Muncie, IN 47306, USA. The purpose of this study was to examine the effects of a 3-wk taper on the physiology of competitive distance runners. We studied seven collegiate distance runners (20+/-1 yr, 66+/-1 kg) before and after a 3-wk taper. The primary measures included 8-km cross-country race performance, gastrocnemius single muscle fiber size and function (peak force, shortening velocity, and power), baseline and exercise-induced gene expression 4 h after a standardized 8-km run, citrate synthase activity, and maximal and submaximal cardiovascular physiology (oxygen consumption, ventilation, heart rate, and respiratory exchange ratio). Race performance improved by 3% following taper (P<0.05). Myosin heavy chain (MHC) IIa fiber diameter (+7%, P<0.05), peak force (+11%, P=0.06), and absolute power (+9%, P<0.05) increased following taper. In addition to the MHC IIa adaptations, taper elicited a distinct postexercise gene response. Specifically, the induction of MuRF-1 was attenuated following taper, whereas MRF4, HSP 72, and MT-2A displayed an exaggerated response (P<0.05). No changes were observed in MHC I size or function, baseline gene expression, citrate synthase activity, or cardiovascular function. Our findings show that tapered training in competitive runners promoted MHC IIa fiber remodeling and an altered transcriptional response following the same exercise perturbation, with no adverse affects on aerobic fitness. Together, these results provide a myocellular basis for distance runners to taper in preparation for peak performance.
Non-invasive indices for the estimation of the anaerobic threshold of oarsmen.Erdogan A, Cetin C, Karatosun H, Baydar ML.: The Journal of International Medical Research, 2010, 38(3):901-15 Language: eng Country: England Department of Sports Medicine, Medical School, Süleyman Demirel University, Isparta, Turkey. This study compared four common non-invasive indices with an invasive index for determining the anaerobic threshold (AT) in 22 adult male rowers using a Concept2 rowing ergometer. A criterion-standard progressive incremental test (invasive method) measured blood lactate concentrations to determine the 4 mmol/l threshold (La4-AT) and Dmax AT (Dm-AT). This was compared with three indices obtained by analysis of respiratory gases and one that was based on the heart rate (HR) deflection point (HRDP) all of which used the Conconi test (non-invasive methods). In the Conconi test, the HRDP was determined whilst continuously increasing the power output (PO) by 25 W/min and measuring respiratory gases and HR. The La4-AT and Dm-AT values differed slightly with respect to oxygen uptake, PO and HR however, AT values significantly correlated with each other and with the four non-invasive methods. In conclusion, the non-invasive indices were comparable with the invasive index and could, therefore, be used in the assessment of AT during rowing ergometer use. In this population of elite rowers, Conconi threshold (Con-AT), based on the measurement of HRDP tended to be the most adequate way of estimating AT for training regulation purposes.
Effect of intermittent hypoxia on muscle and cerebral oxygenation during a 20-km time trial in elite athletes: a preliminary reportMichael J. Hamlin, Helen C. Marshall, John Hellemans, and Philip N. Ainslie: Appl. Physiol. Nutr. Metab. 35(4): 548–559 (2010) .
Nocturnal periodic breathing during acclimatization at very high altitude at Mount Muztagh Ata (7,546 m).Bloch KE, Latshang TD, Turk AJ, Hess T, Hefti U, Merz TM, Bosch MM, Barthelmes D, Hefti JP, Maggiorini M, Schoch OD.: American Journal of Respiratory and Critical Care Medicine, 2010, 182(4):562-8. Department of Internal Medicine, University Hospital of Zurich, Zurich Centre for Integrative Human Physiology, University of Zurich, Switzerland. RATIONALE: Quantitative data on ventilation during acclimatization at very high altitude are scant. Therefore, we monitored nocturnal ventilation and oxygen saturation in mountaineers ascending Mt. Muztagh Ata (7,546 m). OBJECTIVES: To investigate whether periodic breathing persists during prolonged stay at very high altitude. METHODS: A total of 34 mountaineers (median age, 46 yr; 7 women) climbed from 3,750 m within 19-20 days to the summit at 7,546 m. During ascent, repeated nocturnal recordings of calibrated respiratory inductive plethysmography, pulse oximetry, and scores of acute mountain sickness were obtained. MEASUREMENTS AND MAIN RESULTS: Nocturnal oxygen saturation decreased, whereas minute ventilation and the number of periodic breathing cycles increased with increasing altitude. At the highest camp (6,850 m), median nocturnal oxygen saturation, minute ventilation, and the number of periodic breathing cycles were 64%, 11.3 L/min, and 132.3 cycles/h. Repeated recordings within 5-8 days at 4,497 m and 5,533 m, respectively, revealed increased oxygen saturation, but no decrease in periodic breathing. The number of periodic breathing cycles was positively correlated with days of acclimatization, even when controlled for altitude, oxygen saturation, and other potential confounders, whereas symptoms of acute mountain sickness had no independent effect on periodic breathing. CONCLUSIONS: Our field study provides novel data on nocturnal oxygen saturation, breathing patterns, and ventilation at very high altitude. It demonstrates that periodic breathing increases during acclimatization over 2 weeks at altitudes greater than 3,730 m, despite improved oxygen saturation consistent with a progressive increase in loop gain of the respiratory control system.
The six minute walk test accurately estimates mean peak oxygen uptake.Ross RM, Murthy JN, Wollak ID, Jackson AS.: BMC Pulmonary Medicine, 2010, 10:31. Baylor College of Medicine, 3333 Richmond Ave, Houston, Texas 77098, USA. BACKGROUND: Both Peak Oxygen Uptake (peak VO2), from cardiopulmonary exercise testing (CPET) and the distance walked during a Six-Minute Walk Test (6 MWD) are used for following the natural history of various diseases, timing of procedures such as transplantation and for assessing the response to therapeutic interventions. However, their relationship has not been clearly defined. METHODS: We determined the ability of 6 MWD to predict peak VO2 using data points from 1,083 patients with diverse cardiopulmonary disorders. The patient data came from a study we performed and 10 separate studies where we were able to electronically convert published scattergrams to bivariate points. Using Linear Mixed Model analysis (LMM), we determined what effect factors such as disease entity and different inter-site testing protocols contributed to the magnitude of the standard error of estimate (SEE). RESULTS: The LMM analysis found that only 0.16 ml/kg/min or about 4% of the SEE was due to all of the inter-site testing differences. The major source of error is the inherent variability related to the two tests. Therefore, we were able to create a generalized equation that can be used to predict peak VO2 among patients with different diseases, who have undergone various exercise protocols, with minimal loss of accuracy. Although 6 MWD and peak VO2 are significantly correlated, the SEE is unacceptably large for clinical usefulness in an individual patient. For the data as a whole it is 3.82 ml/kg/min or 26.7% of mean peak VO2. Conversely, the SEE for predicting the mean peak VO2 from mean 6 MWD for the 11 study groups is only 1.1 ml/kg/min. CONCLUSIONS: A generalized equation can be used to predict peak VO2 from 6 MWD. Unfortunately, like other prediction equations, it is of limited usefulness for individual patients. However, the generalized equation can be used to accurately estimate mean peak VO2 from mean 6 MWD, among groups of patients with diverse diseases without the need for cardiopulmonary exercise testing. The equation is: Artigo disponível em: http://ukpmc.ac.uk/abstract/MED/20504351;jsessionid=66915E356154AEBE8623ACD0CF361F6C.jvm4
Physiologic and behavioral indicators of energy deficiency in female adolescent runners with elevated bone turnover.Barrack MT, Van Loan MD, Rauh MJ, Nichols JF.: The American Journal of Clinical Nutrition, 2010, 92(3):652-9. University of California Davis, USA. BACKGROUND: Female adolescent runners have an elevated prevalence of low bone mass for agemdashan outcome that may be partially due to inadequate energy intake. OBJECTIVE: The objective was to evaluate diet, menstrual history, serum hormone concentrations, and bone mass in female adolescent runners with normal or abnormal bone turnover. DESIGN: Thirty-nine cross-country runners (age: 15.7 plusmn 0.2 y) participated in the study, which included a 7-d dietary assessment with the use of a food record and daily 24-h dietary recalls; serum measures of insulin-like growth factor I, estradiol, leptin, parathyroid hormone, progesterone, triiodothyronine, 25-hydroxycholecalciferol, bone-specific alkaline phosphatase (BAP), and cross-linked C-telopeptides of type I collagen (CTX); an evaluation of height, weight, bone mass, and body composition with the use of dual-energy X-ray absorptiometry; and a questionnaire to assess menses and sports participation. Age- and sex-specific BAP and CTX concentrations of at least the 97th percentile and no greater than the third percentile, respectively, were considered abnormal. RESULTS: All abnormal BAP and CTX concentrations fell within the elevated ( ge 97%) range. Runners with an elevated bone turnover (EBT) (n = 13) had a lower body mass, fewer menstrual cycles in the past year, lower estradiol and 25-hydroxycholecalciferol concentrations, and a higher prevalence of body mass index lt 10% for age, vitamin D insufficiency, amenorrhea, and low bone mass. Girls with EBT consumed less than the recommended amounts of energy and had a higher prevalence of consuming lt 1300 mg Ca than did those with normal bone turnover. CONCLUSIONS: Runners with EBT had a profile consistent with energy deficiency. Nutritional support to increase energy, calcium intake, and 25-hydroxycholecalciferol concentrations may improve bone mineral accrual in young runners with EBT. This trial was registered at clinicaltrials.gov as NCT01059968.
Loading of trained inspiratory muscles speeds lactate recovery kinetics.Brown PI, Sharpe GR, Johnson MA.: Medicine and Science in Sports and Exercise, 2010, 42(6):1103-12 Optimal Performance Limited, Bristol, United Kingdom. Purpose: The purpose of this study was to investigate the effects of inspiratory threshold loading (ITL) and inspiratory muscle training (IMT) on blood lactate concentration ([lac(-)]B) and acid-base balance after maximal incremental cycling. Methods: Eighteen subjects were divided into a control (n = 9) or an IMT group (n = 9). Before and after a 6-wk intervention, subjects completed two maximal incremental cycling tests followed by 20 min of recovery with (ITL) or without (passive recovery (PR)) a constant inspiratory resistance (15 cm H2O). The IMT group performed 6 wk of pressure threshold IMT at 50% maximal inspiratory mouth pressure. Throughout recovery, acid-base balance was quantified using the physicochemical approach by measuring the strong ion difference ([SID] = [Na+] + [K+] - [Cl-] + [lac-]), the total concentration of weak acids ([Atot-]), and the partial pressure of carbon dioxide (PCO2). Results: After the intervention, maximal inspiratory mouth pressure increased in the IMT group only (+34%). No differences in lactate clearance were observed between PR and ITL before the intervention in both groups and after the intervention in the control group. After IMT, relative to PR, [lac-]B was reduced throughout ITL (minutes 2-20) by 0.66 +/- 1.28 mmol x L(-1) (P < 0.05), and both the fast (lactate exchange) and the slow (lactate clearance) velocity constants of the lactate recovery kinetics were increased (P < 0.05). Relative to pre-IMT, ITL reduced plasma [H], which was accounted for by an IMT-mediated increase in [SID] due almost exclusively to a 1.7-mmol x L(-1) reduction in [lac-]B. Conclusions: After maximal exercise, ITL affected lactate recovery kinetics only after IMT. Our data support the notion that the inspiratory muscles are capable of lactate clearance that increases [SID] and reduces [H+]. These effects may facilitate subsequent bouts of high-intensity exercise.
Physiological effects of tapering and detraining in world-class kayakers.García-Pallarés J, Sánchez-Medina L, Pérez CE, Izquierdo-Gabarren M, Izquierdo M.: Medicine and Science in Sports and Exercise, 2010, 42(6):1209-14. Faculty of Sport Sciences, University of Murcia, Murcia, Spain. Purpose: This study analyzed changes in neuromuscular, body composition, and endurance markers during 4 wk of tapering and subsequent 5 wk of reduced training (RT) or training cessation (TC). METHODS: Fourteen world-class kayakers were randomly assigned to either a TC (n = 7) or an RT group (n = 7). One-repetition maximum (1RM) strength, mean concentric velocity with 45% 1RM (V45%) in the bench press (BP) and prone bench pull (PBP) exercises, and body composition assessments were conducted at the start (T0) and end (T1) of a 43-wk training program, after tapering for the world championships (T2) and after TC or RT (T3). A graded exercise test on a kayak ergometer for determination of maximal oxygen uptake at T0, T1, and T3 was also performed. Results: After tapering, no significant changes were observed in 1RM or V45%. TC resulted in significantly greater declines in 1RM strength (-8.9% and -7.8%, P < 0.05, respectively, for BP and PBP) than those observed for RT (-3.9% and -3.4%). Decreases in V45% in BP and PBP were larger for TC (-12.6% and -10.0%) than for RT (-9.0% and -6.7%). Increases in sum of eight skinfolds were observed after both TC and RT, whereas declines in maximal aerobic power were lower for RT (-5.6%) than for TC (-11.3%). Conclusions: Short-term TC Results in large decreases in maximal strength and especially V45% in highly trained athletes. These Results suggest the need of performing a minimal maintenance program to avoid excessive declines in neuromuscular function in cases where a prolonged break from training is required.
The effect of different dynamic stretch velocities on jump performance.
Fletcher IM.: European Journal of Applied Physiology, 2010, 109(3):491-8 . Department of Sport and Exercise Science, University of Bedfordshire, Polhill Avenue, Bedford, UK. Dynamic stretching has gained popularity, due to a number of studies showing an increase in high intensity performance compared to static stretch modalities. Twenty-four males (age mean 21 +/- 0.3 years) performed a standardised 10 min jogging warm-up followed by either; no stretching (NS), slow dynamic stretching at 50 b/min (SDS) or fast dynamic stretching at 100 b/min (FDS). Post-warm-up, squat, countermovement and depth jumps were performed. Heart rate, tympanic temperature, electromyography (EMG) and kinematic data (100 Hz) were collected during each jump. Results indicated that the FDS condition showed significantly greater jump height in all tests compared to the SDS and NS conditions. Further, the SDS trial resulted in significantly greater performance in the drop and squat jump compared to the NS condition. The reasons behind these performance changes are multi-faceted, but appear to be related to increases in heart rate and core temperature with slow dynamic stretches, while the greater increase in performance for the fast dynamic stretch intervention is linked to greater nervous system activation, shown by significant increases in EMG. In conclusion, a faster dynamic stretch component appears to prepare an athlete for a more optimum performance.
Total protein of whole saliva as a biomarker of anaerobic threshold.
Bortolini MJ, De Agostini GG, Reis IT, Lamounier RP, Blumberg JB, Espindola FS.: Research Quarterly for Exercise and Sport, 2009, 80(3):604-10 . Laboratory of Biomechanics and Molecular Biology, Federal University of Uberlândia, Brazil. Saliva provides a convenient and noninvasive matrix for assessing specific physiological parameters, including some biomarkers of exercise. We investigated whether the total protein concentration of whole saliva (TPWS) would reflect the anaerobic threshold during an incremental exercise test. After a warm-up period, 13 nonsmoking men performed a maximum incremental exercise on a cycle ergometer. Blood and stimulated saliva were collected during the test. The TPWS anaerobic threshold (PAT) was determined using the Dmax method. The PAT was correlated with the blood lactate anaerobic threshold (AT; r = .93, p < .05). No significant difference (p = .16) was observed between PAT and AT. Thus, TPWS provides a convenient and noninvasive matrix for determining the anaerobic threshold during incremental exercise tests.
Intermittent hypoxia does not affect endurance performance at moderate altitude in well-trained athletes.Faulhaber M, Gatterer H, Haider T, Patterson C, Burtscher M.: Journal of Sports Sciences, 2010, 28(5):513-9 . Department of Sport Science, University of Innsbruck, Innsbruck, Austria. In this study, we examined the effects of a pre-acclimatization programme on endurance performance at moderate altitude using a resting intermittent hypoxia protocol. The time-trial performance of 11 cyclists was determined at low altitude (600 m). Athletes were randomly assigned in a double-blind fashion to the hypoxia or the control group. The pre-acclimatization programme consisted of seven sessions each lasting 1 h in normobaric hypoxia (inspired fraction of oxygen of 12.5%, equivalent to approximately 4500 m) for the hypoxia group (n = 6) and in normoxia (inspired fraction of oxygen of 20.9%) for the control group (n = 5). The time-trials were repeated at moderate altitude (1970 m). Mean power output during the time-trial at moderate altitude was decreased in the hypoxia group (-0.26 +/- 0.11 W x kg(-1)) and in the control group (-0.13 +/- 0.04 W x kg(-1)) compared with at low altitude but did not differ between groups (P = 0.13). Our Results suggest that the applied protocol of intermittent hypoxia had no positive effect on endurance performance at moderate altitude. Whether different intermittent hypoxia protocols are advantageous remains to be determined.
Physiological measures tracking seasonal changes in peak running speed.
Saunders PU, Cox AJ, Hopkins WG, Pyne DB.: International Journal of Sports Physiology and Performance, 2010, 5(2):230-8 . Australian Institute of Sport, Canberra, Australia. It is unclear whether physiological measures monitored in an incremental treadmill test during a training season provide useful diagnostic information about changes in distance running performance. Purpose: To quantify the relationship between changes in physiological measures and performance (peak running speed) over a training season. Methods: Well-trained distance runners (34 males; VO2max 64 +/- 6 mL x kg(-1) x min(-1), mean +/- SD) completed four incremental treadmill tests over 17 wk. The tests provided values of peak running speed, VO2max, running economy, and lactate threshold (as speed and %VO2max). The physiological measures were included in simple and multiple linear regression models to quantify the relationship between changes in these measures and changes in peak speed. Results: The typical within-subject variation in peak speed from test to test was 2.5%, whereas those for physiological measures were VO2max (mL x min(-1) x kg(-1)) 3.0%, economy (m x kg x mL(-1)) 3.6%, lactate threshold (%VO2max) 8.7%, and body mass 1.8%. In simple models these typical changes predicted the following changes in performance: VO2max 1.4%, economy 0.8%, lactate threshold -0.3%, and body mass -0.2% (90% confidence limits approximately +/-0.7%); the corresponding correlations with performance were 0.57, 0.33, -0.05, and -0.13 respectively (approximately +/-0.20). In a multiple linear regression model, the contribution of each physiological variable to performance changed little after adjustment for the other variables. Conclusion: Change in VO2max in an incremental test during a running season is a good predictor of change in peak running speed, change in running economy is a moderate predictor, and lactate threshold and body mass provide little additional information.
Maximal and submaximal physiological responses to adaptation to deep water running.Azevedo LB, Lambert MI, Zogaib PS, Barros Neto TL.: Journal of Sports Sciences, 2010, 28(4):407-14 . Health and Social Care Institute, Teeside University, Middlesbrough, UK. The aim of the study was to compare physiological responses between runners adapted and not adapted to deep water running at maximal intensity and the intensity equivalent to the ventilatory threshold. Seventeen runners, either adapted (n = 10) or not adapted (n = 7) to deep water running, participated in the study. Participants in both groups undertook a maximal treadmill running and deep water running graded exercise test in which cardiorespiratory variables were measured. Interactions between adaptation (adapted vs. non-adapted) and condition (treadmill running vs. deep water running) were analysed. The main effects of adaptation and condition were also analysed in isolation. Runners adapted to deep water running experienced less of a reduction in maximum oxygen consumption (VO2max) in deep water running compared with treadmill running than runners not adapted to deep water running. Maximal oxygen consumption, maximal heart rate, maximal ventilation, VO2max at the ventilatory threshold, heart rate at the ventilatory threshold, and ventilation at the ventilatory threshold were significantly higher during treadmill than deep water running. Therefore, we conclude that adaptation to deep water running reduces the difference in VO2max between the two modalities, possibly due to an increase in muscle recruitment. The Results of this study support previous findings of a lower maximal and submaximal physiological response on deep water running for most of the measured parameters.
Prediction of oxygen uptake during level treadmill walking in people with multiple sclerosis.Agiovlasitis S, Motl RW, Fernhall B.: Journal of Rehabilitation Medicine : official Journal of the UEMS European Board of Physical and Rehabilitation Medicine, 2010-07 42(7):650-5. Department of Kinesiology, Mississippi State University, Mississippi State, MS, USA. OBJECTIVE: To determine whether the oxygen uptake (VO2) during walking at different speeds in people with multiple sclerosis is underestimated by available prediction equations and whether such underestimation relates to the validity of their assumptions. DESIGN: Cross-sectional comparison. SUBJECTS: Eighteen adults with MS and 18 adults without MS. METHODS: VO2 was measured at rest and during treadmill walking at 2.0, 3.0 and 4.0 mph with open-circuit spirometry. The actual VO2 was compared with that estimated by both the American College of Sports Medicine and the van der Walt and Wyndham equations. RESULTS: The differences between the actual VO2 and that estimated by both equations were significantly higher than zero across speeds for both groups (p < 0.001). The underestimation increased with increasing speed (p < 0.001) for both groups and was greater for participants with MS than those without MS (p < 0.011). The inaccurate prediction by the American College of Sports Medicine formula was associated with an underestimation of the net VO2 per meter (p < 0.001), and this was higher for participants with MS (p < 0.007). CONCLUSION: Rehabilitation and exercise professionals should recognize that the American College of Sports Medicine and the van der Walt and Wyndham equations underestimate VO2 during treadmill walking in individuals with and without MS.
Vertical jump performance and blood ammonia and lactate levels during typical training sessions in elite 400-m runners.Gorostiaga EM, Asiáin X, Izquierdo M, Postigo A, Aguado R, Alonso JM, Ibáñez J.: Journal of Strength and Conditioning Research / National Strength & Conditioning Association, 2010-04 24(4):1138-49. Research, Studies and Sport Medicine Center, Government of Navarra, Pamplona, Spain. This study described the effects of 6 typical high-intensity intermittent running training sessions of varying distances (60-300 m) and intensities (80-105% of the individual best 400-m record time) on blood ammonia and lactate concentration changes and on vertical jumping height, in twelve 400-m elite male runners. At the end of the training sessions, similar patterns of extremely high blood lactate (14-23 mmol.L) and ammonia levels (50-100 mumol.L) were observed. Vertical jumping performance was maintained during the initial exercise bouts up to a break zone of further increase in the number of exercise bouts, which was associated, especially in subjects with the highest initial vertical jump, with a pronounced decrease (6-28%) in vertical jumping performance, as well as with blood lactate concentrations exceeding 8-12 mmol.L, and blood ammonia levels increasing abruptly from rest values. This break zone may be related to signs of energetic deficiency of the muscle contractile machinery associated with the ability to regenerate adenosine triphosphate at high rates. It is suggested that replacing some of these extremely demanding training sessions with other intermittent training sessions that preserve muscle generating capacity should allow elite athletes to practice more frequently at competitive intensity with lower fatigue.
Talent identification and promotion programmes of Olympic athletes.Vaeyens R, Güllich A, Warr CR, Philippaerts R.: Journal of Sports Sciences, 2009-11- 27(13):1367-80 Department of Movement and Sports Sciences, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium. The start of a new Olympic cycle offers a fresh chance for individuals and nations to excel at the highest level in sport. Most countries attempt to develop systematic structures to identify gifted athletes and to promote their development in a certain sport. However, forecasting years in advance the next generation of sporting experts and stimulating their development remains problematic. In this article, we discuss issues related to the identification and preparation of Olympic athletes. We provide field-based data suggesting that an earlier onset and a higher volume of discipline-specific training and competition, and an extended involvement in institutional talent promotion programmes, during adolescence need not necessarily be associated with greater success in senior international elite sport. Next, we consider some of the promising methods that have been (recently) presented in the literature and applied in the field. Finally, implications for talent identification and promotion and directions for future research are highlighted. Anabolic and catabolic hormones and energy balance of the male bodybuilders during the preparation for the competition.Mäestu J, Eliakim A, Jürimäe J, Valter I, Jürimäe T.: Journal of Strength and Conditioning Research / National Strength & Conditioning Association, 2010-04 24(4):1074-81. Institute of Sport Pedagogy and Coaching Sciences, Center of Behavioral and Health Sciences, University of Tartu, Tartu, Estonia. The purpose of the study was to investigate simultaneous effects of energy balance, caloric intake, and the hormonal anabolic-catabolic balance in bodybuilders prior to competition. Fourteen male bodybuilders took part in an 11-week energy-restricted period to reduce body fat. The subjects were divided into the energy-restricted group (ERG) (n = 7), who were preparing for the competition, or the control group (CG) (n = 7) who continued to train regularly and did not change their dietary or training pattern. Participants were tested at 11 weeks (T1), 5 weeks (T2), and 3 days (T3) before competition for diet, body composition, and fasting hormonal assessment. Body mass and body fat percentage of ERG were significantly (p < 0.05) decreased during the study period. In ERG, insulinlike growth factor-1 (IGF-1) and insulin decreased significantly during the 11-week weight-reduction period (p < 0.05). Testosterone was decreased only from week 11 to week 5 (from 20.3 +/- 6.0 to 18.0 +/- 6.8 nmol/L). Changes in IGF-I concentration were significantly related to changes in insulin (r = 0.741), fat mass (r = 0.705), lean body mass (r = 0.696), and body mass (r = 0.652). Changes in insulin concentrations were significantly related to changes in fat mass (r = 0.630) and lean body mass (r = 0.725). These data indicate that severe energy restriction to extremely low body energy reserves decreases significantly the concentrations of 3 anabolic pathways despite high protein intake. Monitoring of insulin and IGF-1 concentration is suggested to prevent losses in muscle mass in energy-restricted conditions. Other nutritional strategies might be needed to prevent possible catabolic effect during preparation of bodybuilders to competition.
Self-regulation and performance level of elite and non-elite youth soccer players.Toering TT, Elferink-Gemser MT, Jordet G, Visscher C.: Journal of Sports Sciences, 2009-12 27(14):1509-17. Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen, Groningen, Netherlands. In learning and development, self-regulation can be described as the extent to which individuals are metacognitively, motivationally, and behaviourally proactive participants in their learning process (Zimmerman, 1989, 2006). We examined the relationship between self-regulation and performance level in elite (n = 159) and non-elite (n = 285) youth soccer players aged 11-17 years (mean 14.5 years, s = 1.4). The players completed a questionnaire that assessed planning, self-monitoring, evaluation, reflection, effort, and self-efficacy. A logistic regression analysis was performed (controlling for age) to determine which self-regulatory aspects were associated with players' performance level (elite vs. non-elite). High scores on reflection and effort were associated with a higher level of performance. Findings suggest that elite players may be more aware of their strong and weak points as well as better able to translate this awareness into action. In addition, elite players appear to be more willing to invest effort into practice and competition. It is suggested that these better developed self-regulatory skills may translate into a more effective learning environment and ultimately result in an increased capacity for performance in elite players relative to their non-elite peers.
The athlete and high altitude.Derby R, deWeber K. Current sports medicine reports, 2010 Mar-Apr 9(2):79-85. Tri-Service Military Primary Care Sports Medicine Program, Uniformed Services University, Bethesda, MD 20814, USA. Expanding athlete participation in high-altitude environments highlights the importance for a sports physician to have a good understanding of the high-altitude illness (HAI) syndromes: acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). All may occur in the setting of acute altitude exposure higher than 2500 m; incidence and severity increases as altitudes or ascent rates increase. Once HAI is recognized, proven therapies should be instituted to alleviate symptoms and avert the possibility of critical illness. Allowing for acclimatization is the best strategy for preventing HAI. Acetazolamide and dexamethasone are additional preventive measures for AMS/HACE; nifedipine, salmeterol, and phosphodiesterase inhibitors are useful in preventing HAPE. Along with the immediate hazards of HAI with altitude exposure, the sport physician also should be familiar with altitude/hypoxic training practices used by athletes to enhance fitness and performance.
Pacing strategy during the initial phase of the run in triathlon: influence on overall performance.Hausswirth C, Le Meur Y, Bieuzen F, Brisswalter J, Bernard T. European Journal of Applied Physiology 2010, 108(6):1115-23. Laboratory of Biomechanics and Physiology, Research Department, National Institute of Sport, Expertise and Performance (INSEP), 11 Avenue du Tremblay, 75012 Paris, France. The aim of the present study was to determine the best pacing strategy to adopt during the initial phase of a short distance triathlon run for highly trained triathletes. Ten highly trained male triathletes completed an incremental running test to determine maximal oxygen uptake, a 10-km control run at free pace and three individual time-trial triathlons (1.5-km swimming, 40-km cycling, 10-km running) in a randomised order. Swimming and cycling speeds were imposed as identical to the first triathlon performed and the first run kilometre was done alternatively 5% faster (Tri-Run(+5%)), 5% slower (Tri-Run(-5%)) and 10% slower (Tri-Run(-10%)) than the control run (C-Run). The subjects were instructed to finish the 9 remaining kilometres as quickly as possible at a free self-pace. Tri-Run(-5%) resulted in a significantly faster overall 10-km performance than Tri-Run(+5%) and Tri-Run(-10%) (p 0.05) (2,028 +/- 78 s vs. 2,000 +/- 72 s, 2,178 +/- 121 s and 2,087 +/- 88 s, for Tri-Run(-5%), C-Run, Tri-Run(+5%) and Tri-Run(-10%), respectively). Tri-Run(+5%) strategy elicited higher values for oxygen uptake, ventilation, heart rate and blood lactate at the end of the first kilometre than the three other conditions. After 5 and 9.5 km, these values were higher for Tri-Run(-5%) (p < 0.05). The present results showed that the running speed achieved during the cycle-to-run transition is crucial for the improvement of the running phase as a whole. Triathletes would benefit to automate a pace 5% slower than their 10-km control running speed as both 5% faster and 10% slower running speeds over the first kilometre involved weaker overall performances. Yo-Yo intermittent recovery test versus the Université de Montréal Track Test: relation with a high-intensity intermittent exercise.
Dupont G, Defontaine M, Bosquet L, Blondel N, Moalla W, Berthoin S.: Journal of Science and Medicine in Sport / Sports Medicine Australia, 2010, 13(1):146-50 Laboratory of Human Movement Studies, Faculty of Sports Sciences and Physical Education, Artois and Lille 2 Universities, France. The first purpose of this study was to determine whether the peak velocity (V(Yo-Yo)) achieved during the Yo-Yo intermittent recovery test (Yo-Yo) and the maximal aerobic velocity (MAV) determined from the Université de Montréal Track Test (UMTT) could be used interchangeably. The second purpose was to check that the V(Yo-Yo) is related to the intermittent exercise performance, which consisted of repeated 90 m distance runs in 15s performed until exhaustion, alternated with 15s of passive recovery (15/15). Fourteen amateur soccer players performed, in a random order, the 15/15 and two incremental field-tests: the Yo-Yo and the UMTT. The results of this study showed that MAV was significantly correlated to the V(Yo-Yo) (r=0.79, p<0.01). However, the error was not constant, when the V(Yo-Yo) and the MAV values were higher than 16.3 km h(-1), the MAV values tends to be higher than the V(Yo-Yo), while when the V(Yo-Yo) and the MAV values were lower than 16.3 km h(-1), the MAV values tends to be lower than the V(Yo-Yo). MAV and V(Yo-Yo) were significantly correlated to the time to exhaustion of the 15/15 (r=0.74 and r=0.72, respectively) and show that both tests are similarly related to the high-intensity intermittent exercise performance.
Muscle adaptations and performance enhancements of soccer training for untrained men.Krustrup P, Christensen JF, Randers MB, Pedersen H, Sundstrup E, Jakobsen MD, Krustrup BR, Nielsen JJ, Suetta C, Nybo L, Bangsbo J.: European Journal of Applied Physiology, 2010, 108(6):1247-58 Department of Exercise and Sport Sciences, Section of Human Physiology, Copenhagen Muscle Research Centre, University of Copenhagen, The August Krogh Building, Universitetsparken 13, Copenhagen 2100, Denmark. We examined the physical demands of small-sided soccer games in untrained middle-age males and muscle adaptations and performance effects over 12 weeks of recreational soccer training in comparison with continuous running. Thirty-eight healthy subjects (20-43 years) were randomized into a soccer (SO), running (RU) and control (CO) group. Two-three weekly 1-h training sessions were performed. Muscle lactate (30.1 +/- 4.1 vs. 15.6 +/- 3.3 mmol/kg d.w.), blood lactate, blood glucose and time above 90% HR(max) (20 +/- 4% vs. 1 +/- 1%) were higher (p < 0.05) during training in SO than in RU. After 12 weeks of training, quadriceps muscle mass and mean muscle fibre area were 9 and 15% larger (p < 0.05) in SO, but unaltered in RU, and in SO, the fraction of FTx fibres was lowered (10.7 +/- 1.8 vs. 17.9 +/- 3.2%). In SO, citrate synthase activity was 10 and 14% higher (p < 0.05) after 4 and 12 weeks, but unaltered in RU. After 4 weeks VO(2max) and Yo-Yo IE2 performance were elevated (p < 0.05) to a similar extent in SO (7 and 37%) and RU (6 and 36%) but increased further (p < 0.05) from 4 to 12 weeks in SO (6 and 23%). In SO, 30-m sprint performance was improved (p < 0.05) by 0.11 +/- 0.02 s. Blood lactate during running at 11 km/h was lowered (p < 0.05) from 0 to 4 and 4 to 12 weeks (2.6 +/- 0.3 vs. 3.8 +/- 0.6 vs. 6.1 +/- 0.9 mM) and from 0 to 12 weeks in RU. No changes occurred for CO. In conclusion, recreational soccer organized as small-sided games stimulates both aerobic and anaerobic energy turnover and is an effective type of training leading to significant cardiovascular and muscular adaptations as well as performance enhancements throughout a 12-week training period.
Monitoring endurance running performance using cardiac parasympathetic function.Buchheit M, Chivot A, Parouty J, Mercier D, Al Haddad H, Laursen PB, Ahmaidi S.: European Journal of Applied Physiology, 2010, 108(6):1153-67. Germany Research Laboratory, EA 3300 "Laboratory of Exercise Physiology and Rehabilitation", Faculty of Sport Sciences, University of Picardie, Jules Verne, 80025 Amiens, France. The aims of the present study were to (1) assess relationships between running performance and parasympathetic function both at rest and following exercise, and (2) examine changes in heart rate (HR)-derived indices throughout an 8-week period training program in runners. In 14 moderately trained runners (36 +/- 7 years), resting vagal-related HR variability (HRV) indices were measured daily, while exercise HR and post-exercise HR recovery (HRR) and HRV indices were measured fortnightly. Maximal aerobic speed (MAS) and 10 km running performance were assessed before and after the training intervention. Correlations (r > 0.60, P < 0.01) were observed between changes in vagal-related indices and changes in MAS and 10 km running time. Exercise HR decreased progressively during the training period (P 0.5% (responders), resting vagal-related indices showed a progressively increasing trend (time effect P = 0.03) and qualitative indications of possibly and likely higher values during week 7 [+7% (90% CI -3.7;17.0)] and week 9 [+10% (90% CI -1.5;23)] compared with pre-training values, respectively. Post-exercise HRV showed similar changes, despite less pronounced between-group differences. HRR showed a relatively early possible decrease at week 3 [-20% (90% CI -42;10)], with only slight reductions near the end of the program. The results illustrate the potential of resting, exercise and post-exercise HR measurements for both assessing and predicting the impact of aerobic training on endurance running performance. Are there differences in running economy at different velocities for well-trained distance runners?Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, 7489 Trondheim, Norway. The present study investigated whether there are differences in running economy at different velocities for well-trained distance runners, and to what extent a commonly used incremental protocol for measuring oxygen uptake (VO(2)) at different velocities affects the reliability of these measurements. Fifteen well-trained distance runners (9 male and 6 female) participated in this study. Gross oxygen cost of running (C (R)), heart rate (HR) and [La(-)](b) during 5-min runs at velocities ranging from 8.0 to 17 km h(-1), representing intensities ranging from 60 to 90% of maximal oxygen consumption (VO(2max)) was measured on two different days in random order. The athletes were also tested for lactate threshold, VO(2max) and time to exhaustion at MAS ((t)MAS). No significant differences in C (R) between the different relative velocities or the different set velocities were found up to 90% of VO(2max). The incremental protocol for measuring VO(2) at different velocities was found not to affect the reliability of these measurements. All athletes reached their VO(2max) whilst running to exhaustion at MAS. The females showed significantly lower VO(2max), but significantly better C (R) than the males. At velocities representing intensities between 60 and 90% of VO(2max), no differences in C (R) were found. The commonly used incremental protocol for measuring oxygen uptake (VO(2)) at different velocities was found not to affect the reliability of these measurements. This means that C (R) measured at sub-maximal velocities are representative for C (R) at race velocity for distances above 10,000 m for most runners.
Relationships between racing times of Standardbreds and v4 and v200.Lindner AE.: Journal of Animal Science, 2010, 88(3):950-4, Arbeitsgruppe Pferd, D-52428 Juelich, Germany. The objective of the study was to examine the validity of v(4) [velocity run under the defined conditions inducing 4 mmol/L of blood lactate concentration ([LA])] and v(200) (velocity run under the defined conditions inducing a heart rate of 200 beats/min) to differentiate performance level among Standardbred racehorses. For this purpose, 19 Standardbred trotting racehorses with differing racing time records in 2 training yards were submitted to a standardized exercise test to determine their v(4) and v(200) (6 horses of one yard only). The test consisted of 4 or more consecutive intervals depending on when the blood [LA] of a horse increased above 4 mmol/L. Speed and time trotted in each interval as well as time between consecutive intervals were the same for horses of a training yard. The blood [LA] measured after each interval was plotted exponentially against running speed to derive v(4) from the blood lactate-running speed relationship, and the mean heart rate during the intervals was plotted linearly against running speed to derive v(200) from the heart rate-running speed relationship. The correlation coefficient between v(4) and the racing time record was 0.77 and 0.75 for horses in racing yard A and B, respectively. There was no correlation between v(200) and the racing time record. Therefore, v(4) is a valid indicator of performance level of Standardbred trotting racehorses; however, v(200) may not be or to a lesser extent.
Recovery of heart rate following intense dynamic exercise.Coote JH.: Experimental Physiology, 2010, 95(3):431-40.of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.. The Olympic biathlon is a very demanding physical event that requires high oxygen delivery, good cross-country skiing skills and skilful use of a rifle. Like all high-performance endurance athletes, high cardiac vagal tone is a characteristic and extends the range over which cardiac output can increase. In the biathlete, however, the enhanced vagal control of the heart also allows a strategy for better control of stability needed for accurately firing a rifle at the end of each lap of the race. The role of endurance training, central command, reflexes from muscle, and of the carotid-cardiac baroreceptor reflex in changing vagal tone during intense exercise and recovery is discussed.
Acute signalling responses to intense endurance training commenced with low or normal muscle glycogen.Yeo WK, McGee SL, Carey AL, Paton CD, Garnham AP, Hargreaves M, Hawley JA.: Experimental Physiology, 2010, 95(2):351-8.Exercise Metabolism Group, School of Medical Sciences, RMIT University, PO Box 71, Bundoora, VIC 3083, Australia. We have previously demonstrated that well-trained subjects who completed a 3 week training programme in which selected high-intensity interval training (HIT) sessions were commenced with low muscle glycogen content increased the maximal activities of several oxidative enzymes that promote endurance adaptations to a greater extent than subjects who began all training sessions with normal glycogen levels. The aim of the present study was to investigate acute skeletal muscle signalling responses to a single bout of HIT commenced with low or normal muscle glycogen stores in an attempt to elucidate potential mechanism(s) that might underlie our previous observations. Six endurance-trained cyclists/triathletes performed a 100 min ride at approximately 70% peak O(2) uptake (AT) on day 1 and HIT (8 x 5 min work bouts at maximal self-selected effort with 1 min rest) 24 h later (HIGH). Another six subjects, matched for fitness and training history, performed AT on day 1 then 1-2 h later, HIT (LOW). Muscle biopsies were taken before and after HIT. Muscle glycogen concentration was higher in HIGH versus LOW before the HIT (390 +/- 28 versus 256 +/- 67 micromol (g dry wt)(1)). After HIT, glycogen levels were reduced in both groups (P < 0.05) but HIGH was elevated compared with LOW (229 +/- 29 versus 124 +/- 41 micromol (g dry wt)(1); P < 0.05). Phosphorylation of 5 AMP-activated protein kinase (AMPK) increased after HIT, but the magnitude of increase was greater in LOW (P < 0.05). Despite the augmented AMPK response in LOW after HIT, selected downstream AMPK substrates were similar between groups. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) was unchanged for both groups before and after the HIT training sessions. We conclude that despite a greater activation AMPK phosphorylation when HIT was commenced with low compared with normal muscle glycogen availability, the localization and phosphorylation state of selected downstream targets of AMPK were similar in response to the two interventions.
Apnea: a new training method in sport?Lemaître F, Joulia F, Chollet D.: Medical Hypotheses, 2010, 74(3):413-5. Faculté des Sciences du Sport et de l'Education Physique de Rouen, Centre d'Etudes des Transformations des Activités Physiques et Sportives, Equipe d'Accueil UPRES N degrees 3832, Université de Rouen, France. The physiological responses to apnea training exhibited by elite breath-hold divers may contribute to improving sports performance. Breath-hold divers have shown reduced blood acidosis, oxidative stress and basal metabolic rate, and increased hematocrit, erythropoietin concentration, hemoglobin mass and lung volumes. We hypothesise that these adaptations contributed to long apnea durations and improve performance. These results suggest that apnea training may be an effective alternative to hypobaric or normobaric hypoxia to increase aerobic and/or anaerobic performance.
Exercise at given percentages of VO2max: heterogeneous metabolic responses between individuals.Scharhag-Rosenberger F, Meyer T, Gässler N, Faude O, Kindermann W.: Journal of science and medicine in sport / Sports Medicine Australia, 201001 13(1):74-9.Institute of Sports and Preventive Medicine, University of Saarland, Saarbrücken, Germany. PURPOSE: Given percentages of VO(2max) are widely used for training and study purposes although they might not result in homogeneous metabolic strain. Therefore, the homogeneity of metabolic responses to prolonged exercise at fixed percentages of VO(2max) should be investigated. Procedures: Twenty-one healthy male subjects (29+/-5 years, 77+/-8 kg, VO(2max): 59.9+/-11.8 ml min(-1)kg(-1)) performed two incremental tests to exhaustion on a cycle ergometer to determine VO(2max). Subsequently, two 60 min tests at 60 and 75% VO(2max) were conducted in randomised order. VO(2) was kept constant by adjusting the work rate. Blood lactate (La) responses as primary outcome variable to quantify metabolic strain were assessed. Findings: Mean La was 2.1+/-1.1 mmol l(-1) (min-max: 0.7-5.6 mmol l(-1)) during the 60% VO(2max) test and 4.6+/-1.9 mmol l(-1) (min-max: 2.2-8.0 mmol l(-1)) during the 75% VO(2max) test. The coefficients of variation of La amounted for 52.4 and 41.3% during the 60 and 75% VO(2max) test, respectively. La responses did not differ significantly between three subgroups of the subjects (N=7 with VO(2max)65 ml min(-1)kg(-1); P>or=0.08). Conclusion: Altogether, prolonged exercise at given percentages of VO(2max) leads to inhomogeneous metabolic strain as indicated by the large variability of La responses. This holds true even in subgroups of similar aerobic capacity. Thus, intensity prescription for endurance training and study purposes should not be solely based upon percentages of VO(2max) when a comparable metabolic strain is intended.
Physiological determinants of Yo-Yo intermittent recovery tests in male soccer players.Rampinini E, Sassi A, Azzalin A, Castagna C, Menaspà P, Carlomagno D, Impellizzeri FM European Journal of Applied Physiology, 201001 108(2):401-9. Human Performance Laboratory, MAPEI Sport Research Center, Castellanza, Varese, Italy. The physiological determinants of performance in two Yo-Yo intermittent recovery tests (Yo-YoIR1 and Yo-YoIR2) were examined in 25 professional (n = 13) and amateur (n = 12) soccer players. The aims of the study were (1) to examine the differences in physiological responses to Yo-YoIR1 and Yo-YoIR2, (2) to determine the relationship between the aerobic and physiological responses to standardized high-intensity intermittent exercise (HIT) and Yo-Yo performance, and (3) to investigate the differences between professional and amateur players in performance and responses to these tests. All players performed six tests: two versions of the Yo-Yo tests, a test for the determination of maximum oxygen uptake ([Formula: see text]), a double test to determine [Formula: see text] kinetics and a HIT evaluation during which several physiological responses were measured. The anaerobic contribution was greatest during Yo-YoIR2. [Formula: see text] was strongly correlated with Yo-YoIR1 (r = 0.74) but only moderately related to Yo-YoIR2 (r = 0.47). The time constant (tau) of [Formula: see text] kinetics was largely related to both Yo-Yo tests (Yo-YoIR1: r = 0.60 and Yo-YoIR2: r = 0.65). The relationships between physiological variables measured during HIT (blood La(-), H(+), HCO(3) (-) and the rate of La(-) accumulation) and Yo-Yo performance (in both versions) were very large (r > 0.70). The physiological responses to HIT and the tau of the [Formula: see text] kinetics were significantly different between professional and amateur soccer players, whilst [Formula: see text] was not significantly different between the two groups. In conclusion, [Formula: see text] is more important for Yo-YoIR1 performance, whilst tau of the [Formula: see text] kinetics and the ability to maintain acid-base balance are important physiological factors for both Yo-Yo tests.
Yo-Yo intermittent recovery test versus the Université de Montréal Track Test: relation with a high-intensity intermittent exercise.Dupont G, Defontaine M, Bosquet L, Blondel N, Moalla W, Berthoin S.: Journal of Science and Medicine in Sport / Sports Medicine Australia, 201001 13(1):146-50. Laboratory of Human Movement Studies, Faculty of Sports Sciences and Physical Education, Artois and Lille 2 Universities, France. The first Purpose of this study was to determine whether the peak velocity (V(Yo-Yo)) achieved during the Yo-Yo intermittent recovery test (Yo-Yo) and the maximal aerobic velocity (MAV) determined from the Université de Montréal Track Test (UMTT) could be used interchangeably. The second Purpose was to check that the V(Yo-Yo) is related to the intermittent exercise performance, which consisted of repeated 90 m distance runs in 15s performed until exhaustion, alternated with 15s of passive recovery (15/15). Fourteen amateur soccer players performed, in a random order, the 15/15 and two incremental field-tests: the Yo-Yo and the UMTT. The results of this study showed that MAV was significantly correlated to the V(Yo-Yo) (r=0.79, p<0.01). However, the error was not constant, when the V(Yo-Yo) and the MAV values were higher than 16.3 km h(-1), the MAV values tends to be higher than the V(Yo-Yo), while when the V(Yo-Yo) and the MAV values were lower than 16.3 km h(-1), the MAV values tends to be lower than the V(Yo-Yo). MAV and V(Yo-Yo) were significantly correlated to the time to exhaustion of the 15/15 (r=0.74 and r=0.72, respectively) and show that both tests are similarly related to the high-intensity intermittent exercise performance.
Recovery of heart rate following intense dynamic exercise.Coote JH.: Experimental Physiology, 201003 95(3):431-40. School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. The Olympic biathlon is a very demanding physical event that requires high oxygen delivery, good cross-country skiing skills and skilful use of a rifle. Like all high-performance endurance athletes, high cardiac vagal tone is a characteristic and extends the range over which cardiac output can increase. In the biathlete, however, the enhanced vagal control of the heart also allows a strategy for better control of stability needed for accurately firing a rifle at the end of each lap of the race. The role of endurance training, central command, reflexes from muscle, and of the carotid-cardiac baroreceptor reflex in changing vagal tone during intense exercise and recovery is discussed.
Acute signalling responses to intense endurance training commenced with low or normal muscle glycogen.
Yeo WK, McGee SL, Carey AL, Paton CD, Garnham AP, Hargreaves M, Hawley JA.: Experimental Physiology. 201002 95(2):351-8. Exercise Metabolism Group, School of Medical Sciences, RMIT University, PO Box 71, Bundoora, VIC 3083, Australia. We have previously demonstrated that well-trained subjects who completed a 3 week training programme in which selected high-intensity interval training (HIT) sessions were commenced with low muscle glycogen content increased the maximal activities of several oxidative enzymes that promote endurance adaptations to a greater extent than subjects who began all training sessions with normal glycogen levels. The aim of the present study was to investigate acute skeletal muscle signalling responses to a single bout of HIT commenced with low or normal muscle glycogen stores in an attempt to elucidate potential mechanism(s) that might underlie our previous observations. Six endurance-trained cyclists/triathletes performed a 100 min ride at approximately 70% peak O(2) uptake (AT) on day 1 and HIT (8 x 5 min work bouts at maximal self-selected effort with 1 min rest) 24 h later (HIGH). Another six subjects, matched for fitness and training history, performed AT on day 1 then 1-2 h later, HIT (LOW). Muscle biopsies were taken before and after HIT. Muscle glycogen concentration was higher in HIGH versus LOW before the HIT (390 +/- 28 versus 256 +/- 67 micromol (g dry wt)(1)). After HIT, glycogen levels were reduced in both groups (P < 0.05) but HIGH was elevated compared with LOW (229 +/- 29 versus 124 +/- 41 micromol (g dry wt)(1); P < 0.05). Phosphorylation of 5 AMP-activated protein kinase (AMPK) increased after HIT, but the magnitude of increase was greater in LOW (P < 0.05). Despite the augmented AMPK response in LOW after HIT, selected downstream AMPK substrates were similar between groups. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) was unchanged for both groups before and after the HIT training sessions. We conclude that despite a greater activation AMPK phosphorylation when HIT was commenced with low compared with normal muscle glycogen availability, the localization and phosphorylation state of selected downstream targets of AMPK were similar in response to the two interventions.
Apnea: a new training method in sport?Lemaître F, Joulia F, Chollet D.: Medical Hypotheses, 201003 74(3):413-5. Faculté des Sciences du Sport et de l'Education Physique de Rouen, Centre d'Etudes des Transformations des Activités Physiques et Sportives, Equipe d'Accueil UPRES N degrees 3832, Université de Rouen, France. The physiological responses to apnea training exhibited by elite breath-hold divers may contribute to improving sports performance. Breath-hold divers have shown reduced blood acidosis, oxidative stress and basal metabolic rate, and increased hematocrit, erythropoietin concentration, hemoglobin mass and lung volumes. We hypothesise that these adaptations contributed to long apnea durations and improve performance. These results suggest that apnea training may be an effective alternative to hypobaric or normobaric hypoxia to increase aerobic and/or anaerobic performance.
Exercise at given percentages of VO2max: heterogeneous metabolic responses between individuals.
Scharhag-Rosenberger F, Meyer T, Gässler N, Faude O, Kindermann W.: Journal of Science and Medicine in Sport / Sports Medicine Australia, 201001 13(1):74-9. Institute of Sports and Preventive Medicine, University of Saarland, Saarbrücken, Germany. Purpose: Given percentages of VO(2max) are widely used for training and study Purposes although they might not result in homogeneous metabolic strain. Therefore, the homogeneity of metabolic responses to prolonged exercise at fixed percentages of VO(2max) should be investigated. Procedures: Twenty-one healthy male subjects (29+/-5 years, 77+/-8 kg, VO(2max): 59.9+/-11.8 ml min(-1)kg(-1)) performed two incremental tests to exhaustion on a cycle ergometer to determine VO(2max). Subsequently, two 60 min tests at 60 and 75% VO(2max) were conducted in randomised order. VO(2) was kept constant by adjusting the work rate. Blood lactate (La) responses as primary outcome variable to quantify metabolic strain were assessed. Findings: Mean La was 2.1+/-1.1 mmol l(-1) (min-max: 0.7-5.6 mmol l(-1)) during the 60% VO(2max) test and 4.6+/-1.9 mmol l(-1) (min-max: 2.2-8.0 mmol l(-1)) during the 75% VO(2max) test. The coefficients of variation of La amounted for 52.4 and 41.3% during the 60 and 75% VO(2max) test, respectively. La responses did not differ significantly between three subgroups of the subjects (N=7 with VO(2max)65 ml min(-1)kg(-1); P>or=0.08). Conclusion: Altogether, prolonged exercise at given percentages of VO(2max) leads to inhomogeneous metabolic strain as indicated by the large variability of La responses. This holds true even in subgroups of similar aerobic capacity. Thus, intensity prescription for endurance training and study Purposes should not be solely based upon percentages of VO(2max) when a comparable metabolic strain is intended.
Modificado em 31 de Maio de 2010
Higher fat oxidation in running than cycling at the same exercise intensities.Capostagno B, Bosch A.: International Journal of Sport Nutrition and Exercise Metabolism, 2010, 20(1):44-55. Dept. of Human Biology, University of Cape Town, South Africa. This study examined the differences in fat and carbohydrate oxidation during running and cycling at the same relative exercise intensities, with intensity determined in a number of ways. Specifically, exercise intensity was expressed as a percentage of maximum workload (WL(max)), maximum oxygen uptake (%VO(2max)), and maximum heart rate (%HR(max)) and as rating of perceived exertion (RPE). Ten male triathletes performed maximal running and cycling trials and subsequently exercised at 60%, 65%, 70%, 75%, and 80% of their WL(max). VO(2), HR, RPE, and plasma lactate concentrations were measured during all submaximal trials. Fat and carbohydrate oxidation were calculated from VO(2) and VCO(2) data. A 2-way ANOVA for repeated measures was used to determine any statistically significant differences between exercise modes. Fat oxidation was shown to be significantly higher in running than in cycling at the same relative intensities expressed as either %WL(max) or %VO(2max). Neither were there any significant differences in VO(2max) and HR(max) between the 2 exercise modes, nor in submaximal VO(2) or RPE between the exercise modes at the same %WL(max). However, heart rate and plasma lactate concentrations were significantly higher when cycling at 60% and 65% and 65-80%WL(max), respectively. In conclusion, fat oxidation is significantly higher during running than during cycling at the same relative intensity expressed as either %WL(max) or %VO(2max).
Modificado: 22 de Maio de 2010 |