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1.
Abstract

The aim of this study was to assess the effect of intermittent hypoxia exposure on direct and indirect methods used to evaluate recombinant human erythropoietin (rhEPO) misuse. Sixteen male triathletes were randomly assigned to either the intermittent hypoxia exposure group (experimental group) or the control normoxic group (control group). The members of the experimental group were exposed to simulated altitude (from 4000 to 5500 m) in a hypobaric chamber for 3 h per day, 5 days a week, for 4 weeks. Blood and urine samples were collected before and after the first and the final exposures, and again 2 weeks after the final exposure. While serum EPO significantly increased after the first [from a mean 8.3 IU · l?1 (s = 3.2) to 16.6 IU · l?1 (s = 4.7)] and final exposures [from 4.6 IU · l?1 (s = 1.4) to 24.8 IU · l?1 (s = 9.3)], haemoglobin, percentage of reticulocytes, and soluble transferrin receptor were not elevated. Second-generation ON/OFF models (indirect rhEPO misuse detection) were insensitive to intermittent hypoxia exposure. The distribution of the urinary EPO isoelectric profiles (direct rhEPO misuse detection) was altered after intermittent hypoxia exposure with a slight shift towards more basic isoforms. However, those shifts never resulted in misinterpretation of results. The intermittent hypoxia exposure protocol studied did not produce any false-positive result for indirect or direct detection of rhEPO misuse in spite of the changes in EPO serum concentrations and urinary EPO isoelectric profiles, respectively.  相似文献   

2.
高住低训中EPO变化规律的研究   总被引：2，自引：0，他引：2  
血清EPO(erythropoietin，促红细胞生成素)与红细胞的生成有密切关系。为确切了解EPO在高住低训中的变化规律，将14名大学生分为高住低训组和低住低训组，每组7人。高住低训组每天低压低氧(2500m模拟高度)暴露12小时；低住低训组在实验期间不进行低氧暴露。两组每天在常压常氧环境下进行一次3000m跑训练。实验为期4周。结果表明，促红细胞生成素在间断性低氧暴露初期就有升高变化，1天后出现高峰，这一高EPO水平一直维持到低压氧暴露结束。另外，对第2次低氧暴露完当天出低压氧仓即刻与常氧暴露10h后所测EPO结果的比较表明，常氧暴露后EPO呈下降趋势，说明间断性低氧暴露对EPO生成存在着慢性积累的过程。低住低训组的EPO水平一直比较平稳，说明常氧环境对EPO的分泌无明显影响。  相似文献   

3.
间歇低氧训练对大鼠肾脏EPO基因表达的影响   总被引：1，自引：0，他引：1  
为探讨间歇低氧训练对大鼠肾脏。EPO mRNA基因表达的影响,为高原训练方案的制定提供理论依据,用RT-PCR技术检测大鼠肾脏。EPOmRNA水平。结果表明急性低氧应激后大鼠肾脏EPO mRNA表达水平均显著性升高(P<0.05),急性低氧运动组升高极显著(P<0.01);海拔3000 m间歇低氧训练组EPO mRNA表达水平显著性升高(P<0.05)。认为海拔3000 m的间歇低氧训练能稳定EPO mRNA表达的上调。提示3000 m的海拔高度可能是较适宜间歇低氧训练的海拔高度。  相似文献   

4.
rhEPO可通过增加机体红细胞数目和血红蛋白含量，提高最大吸氧量，从而增强运动员耐力，但滥用rhEPO可能对运动员身体造成很大危害。尽管近10年来，直接和间接的方法都被应用于rhEPO的检测，但没有一个间接指标能达到令人满意的检验效果。在悉尼奥运会上，国际奥委会采用了一种综合血检和尿检的方法来检测rhEPO。此外，在将来可能有人会采用例如基因兴奋剂的方法来提高氧转运能力。  相似文献   

5.
运动与促红细胞生成素   总被引：5，自引：0，他引：5  
介绍促红细胞生成素(EPO)的来源及生物学活性,综述近年来国内外有关运动与EPO的研究成果:分析急性运动及长期耐力运动对血浆EPO的影响;高原训练后EPO的变化情况;提出EPO可作为耐力运动训练的评价预测指标;最后就rhEPO作为兴奋剂的使用、危害及检测作了介绍。  相似文献   

6.
The aim of this study was to assess the effects of cold-water immersion (cryotherapy) on indices of muscle damage following a bout of prolonged intermittent exercise. Twenty males (mean age 22.3 years, s = 3.3; height 1.80 m, s = 0.05; body mass 83.7 kg, s = 11.9) completed a 90-min intermittent shuttle run previously shown to result in marked muscle damage and soreness. After exercise, participants were randomly assigned to either 10 min cold-water immersion (mean 10 degrees C, s = 0.5) or a non-immersion control group. Ratings of perceived soreness, changes in muscular function and efflux of intracellular proteins were monitored before exercise, during treatment, and at regular intervals up to 7 days post-exercise. Exercise resulted in severe muscle soreness, temporary muscular dysfunction, and elevated serum markers of muscle damage, all peaking within 48 h after exercise. Cryotherapy administered immediately after exercise reduced muscle soreness at 1, 24, and 48 h (P < 0.05). Decrements in isometric maximal voluntary contraction of the knee flexors were reduced after cryotherapy treatment at 24 (mean 12%, s(x) = 4) and 48 h (mean 3%, s(x) = 3) compared with the control group (mean 21%, s(x) = 5 and mean 14%, s(x) = 5 respectively; P < 0.05). Exercise-induced increases in serum myoglobin concentration and creatine kinase activity peaked at 1 and 24 h, respectively (P < 0.05). Cryotherapy had no effect on the creatine kinase response, but reduced myoglobin 1 h after exercise (P < 0.05). The results suggest that cold-water immersion immediately after prolonged intermittent shuttle running reduces some indices of exercise-induced muscle damage.  相似文献   

7.
Abstract

To quantify the effects of adaptation to acutely intermittent hypoxia on running performance, we randomized 29 trained male hockey and soccer players in double-blind fashion to altitude or placebo groups for 15 days of daily use of a functional or placebo hypoxic re-breathing device. Each day's exposure consisted of alternately breathing stale and fresh air for 6 and 4 min respectively over 1 h. Oxygen saturation was monitored with pulse oximeters and progressively reduced in the hypoxia group (90% on Day 1, 77% on Day 15; equivalent to altitudes of ～3600–6000 m above sea level). Performance tests were an incremental run to maximum speed followed by six maximal-effort running sprints; tests were performed 1 day before, 3 days after, and 12 days after the 15-day treatment. Relative to placebo, at 3 days post treatment the hypoxia group showed a mean increase in maximum speed of 2.0% (90% confidence limits, ±0.5%); sprint speed was relatively faster by 1.5% (±1.7%) in the first sprint through 7.0% (±1.5%) in the last; there were also substantial reductions in exercise lactate concentration and resting and exercise heart rate. Substantial effects on performance were still present 9 days later. Thus, adaptation to acutely intermittent hypoxia substantially improves high-intensity running performance.  相似文献   

8.
To investigate the benefits of 'living high and training low' on anaerobic performance at sea level, eight 400-m runners lived for 10 days in normobaric hypoxia in an altitude house (oxygen content = 15.8%) and trained outdoors in ambient normoxia at sea level. A maximal anaerobic running test and 400-m race were performed before and within 1 week of living in the altitude house to determine the maximum speed and the speeds at different submaximal blood lactate concentrations (3, 5, 7, 10 and 13 mmol x l(-1)) and 400-m race time. At the same time, ten 400-m runners lived and trained at sea level and were subjected to identical test procedures. Multivariate analysis of variance indicated that the altitude house group but not the sea-level group improved their 400-m race time during the experimental period (P < 0.05). The speeds at blood lactate concentrations of 5-13 mmol x l(-1) tended to increase in the altitude house group but the response was significant only at 5 and 7 mmol x l(-1) (P < 0.05). Furthermore, resting blood pH was increased in six of the eight altitude house athletes from 0.003 to 0.067 pH unit (P < 0.05). The results of this study demonstrate improved 400-m performance after 10 days of living in normobaric hypoxia and training at sea level. Furthermore, the present study provides evidence that changes in the acid-base balance and lactate metabolism might be responsible for the improvement in sprint performance.  相似文献   

9.
To examine the activity profile and physiological demands of top-class soccer refereeing, we performed computerized time-motion analyses and measured the heart rate and blood lactate concentration of 27 referees during 43 competitive matches in the two top Danish leagues. To relate match performance to physical capacity and training, several physiological tests were performed before and after intermittent exercise training. Total distance covered was 10.07+/-0.13 km (mean +/- s(x)), of which 1.67+/-0.08 km was high-intensity running. High-intensity running and backwards running decreased (P < 0.05) in the second half. Mean heart rate was 162+/-2 beats min(-1) (85+/-1% of maximal heart rate) and the mean blood lactate concentration was 4.9+/-0.3 (range 1.7-14.0) mmol x l(-1). The amount of high-intensity running during a match was related to the Yo-Yo intermittent recovery test (r2 = 0.57; P<0.05) and the 12 min run (r2 = 0.21; P<0.05). After intermittent training (n = 8), distance covered during high-intensity running was greater (2.06+/-0.13 vs 1.69+/-0.08 km; P< 0.05) and mean heart rate was lower (159+/-1 vs 164+/-2 beats x min(-1); P< 0.05) than before training. The results of the present study demonstrate that: (1) top-class soccer referees have significant aerobic energy expenditure throughout a game and episodes of considerable anaerobic energy turnover; (2) the ability to perform high-intensity running is reduced towards the end of matches; (3) the Yo-Yo intermittent recovery test can be used to evaluate referees' match performance; and (4) intense intermittent exercise training improves referees' performance capacity during a game.  相似文献   

10.
The aim of the study was to examine several physiological responses to a climbing-specific task to identify determinants of endurance in sport rock climbing. Finger strength and endurance of intermediate rock climbers (n = 11) and non-climbers (n = 9) were compared using climbing-specific apparatus. After maximum voluntary contraction (MVC) trials, two isometric endurance tests were performed at 40% (s = 2.5%) MVC until volitional exhaustion (continuous contractions and intermittent contractions of 10 s, with 3 s rest between contractions). Changes in muscle blood oxygenation and muscle blood volume were recorded in the flexor digitorum superficialis using near infra-red spectroscopy. Statistical significance was set at P < 0.05. Climbers had a higher mean MVC (climbers: 485 N, s = 65; non-climbers 375 N, s = 91) (P = 0.009). The group mean endurance test times were similar. The force-time integral, used as a measure of climbing-specific endurance, was greater for climbers in the intermittent test (climbers: 51,769 N x s, s = 12,229; non-climbers: 35,325 N x s, s = 9724) but not in the continuous test (climbers: 21,043 N x s, s = 4474; non-climbers: 15,816 N x s, s = 6263). Recovery of forearm oxygenation during rest phases (intermittent test) explained 41.1% of the variability in the force-time integral. Change in total haemoglobin was significantly greater in non-climbers (continuous test) than climbers (P = 0.023--40% test timepoint, P = 0.014--60% test timepoint). Pressor responses were similar between groups and not related to the force-time integral for either test. We conclude that muscle re-oxygenation during rest phases is a predictor of endurance performance.  相似文献   

11.
It has previously been shown that measurement of the critical speed is a non-invasive method of estimating the blood lactate response during exercise. However, its validity in children has yet to be demonstrated. The aims of this study were: (1) to verify if the critical speed determined in accordance with the protocol of Wakayoshi et al. is a non-invasive means of estimating the swimming speed equivalent to a blood lactate concentration of 4 mmol x l(-1) in children aged 10-12 years; and (2) to establish whether standard of performance has an effect on its determination. Sixteen swimmers were divided into two groups: beginners and trained. They initially completed a protocol for determination of speed equivalent to a blood lactate concentration of 4 mmol x l(-1). Later, during training sessions, maximum efforts were swum over distances of 50, 100 and 200 m for the calculation of the critical speed. The speeds equivalent to a blood lactate concentration of 4 mmol x l(-1) (beginners = 0.82 +/- 0.09 m x s(-1), trained = 1.19 +/- 0.11 m x s(-1); mean +/- s) were significantly faster than the critical speeds (beginners = 0.78 +/- 0.25 m x s(-1), trained = 1.08 +/- 0.04 m x s(-1)) in both groups. There was a high correlation between speed at a blood lactate concentration of 4 mmol x l(-1) and the critical speed for the beginners (r= 0.96, P < 0.001), but not for the trained group (r= 0.60, P> 0.05). The blood lactate concentration corresponding to the critical speed was 2.7 +/- 1.1 and 3.1 +/- 0.4 mmol x l(-1) for the beginners and trained group respectively. The percent difference between speed at a blood lactate concentration of 4 mmol x l(-1) and the critical speed was not significantly different between the two groups. At all distances studied, swimming performance was significantly faster in the trained group. Our results suggest that the critical speed underestimates swimming intensity corresponding to a blood lactate concentration of 4 mmol x l(-1) in children aged 10-12 years and that standard of performance does not affect the determination of the critical speed.  相似文献   

12.
To examine the activity profile and physiological demands of top-class soccer refereeing, we performed computerized time-motion analyses and measured the heart rate and blood lactate concentration of 27 referees during 43 competitive matches in the two top Danish leagues. To relate match performance to physical capacity and training, several physiological tests were performed before and after intermittent exercise training. Total distance covered was 10.07 - 0.13 km (mean - s x ), of which 1.67 - 0.08 km was high-intensity running. High-intensity running and backwards running decreased (P ? 0.05) in the second half. Mean heart rate was 162 - 2 beats· min -1 (85 - 1% of maximal heart rate) and the mean blood lactate concentration was 4.9 - 0.3 (range 1.7-14.0) mmol·l -1 . The amount of high-intensity running during a match was related to the Yo-Yo intermittent recovery test ( r 2 = 0.57; P ? 0.05) and the 12 min run ( r 2 = 0.21; P ? 0.05). After intermittent training ( n = 8), distance covered during high-intensity running was greater (2.06 - 0.13 vs 1.69 - 0.08 km; P ? 0.05) and mean heart rate was lower (159 - 1 vs 164 - 2 beats· min -1 ; P ? 0.05) than before training. The results of the present study demonstrate that: (1) top-class soccer referees have significant aerobic energy expenditure throughout a game and episodes of considerable anaerobic energy turnover; (2) the ability to perform high-intensity running is reduced towards the end of matches; (3) the Yo-Yo intermittent recovery test can be used to evaluate referees' match performance; and (4) intense intermittent exercise training improves referees' performance capacity during a game.  相似文献   

13.
Exercise intensity and metabolic response in singles tennis   总被引：5，自引：0，他引：5  
The aim of this study was to determine exercise intensity and metabolic response during singles tennis play. Techniques for assessment of exercise intensity were studied on-court and in the laboratory. The on-court study required eight State-level tennis players to complete a competitive singles tennis match. During the laboratory study, a separate group of seven male subjects performed an intermittent and a continuous treadmill run. During tennis play, heart rate (HR) and relative exercise intensity (72 +/- 1.9% VO2max; estimated from measurement of heart rate) remained constant (83.4 +/- 0.9% HRmax; mean +/- s(x)) after the second change of end. The peak value for estimated play intensity (1.25 +/- 0.11 steps x s(-1); from video analysis) occurred after the fourth change of end (P< 0.005). Plasma lactate concentration, measured at rest and at the change of ends, increased 175% from 2.13 +/- 0.32 mmol x l(-1) at rest to a peak 5.86 +/- 1.33 mmol x l(-1) after the sixth change of end (P < 0.001). A linear regression model, which included significant terms for %HRmax (P< 0.001), estimated play intensity (P < 0.001) and subject (P < 0.00), as well as a %HRmax subject interaction (P < 0.05), accounted for 82% of the variation in plasma lactate concentration. During intermittent laboratory treadmill running, % VO2peak estimated from heart rate was 17% higher than the value derived from the measured VO2 (79.7 +/- 2.2% and 69.0 +/- 2.5% VO2peak respectively; P< 0.001). The %VO2peak was estimated with reasonable accuracy during continuous treadmill running (5% error). We conclude that changes in exercise intensity based on measurements of heart rate and a time-motion analysis of court movement patterns explain the variation in lactate concentration observed during singles tennis, and that measuring heart rate during play, in association with preliminary fitness tests to estimate VO2, will overestimate the aerobic response.  相似文献   

14.
Strenuous physical exercise of the limb muscles commonly results in damage, especially when that exercise is intense, prolonged and includes eccentric contractions. Many factors contribute to exercise-induced muscle injury and the mechanism is likely to differ with the type of exercise. Competitive sports players are highly susceptible to this type of injury. AM3 is an orally administered immunomodulator that reduces the synthesis of proinflammatory cytokines and normalizes defective cellular immune fractions. The ability of AM3 to prevent chronic muscle injury following strenuous exercise characterized by eccentric muscle contraction was evaluated in a double-blind and randomized pilot study. Fourteen professional male volleyball players from the First Division of the Spanish Volleyball League volunteered to take part. The participants were randomized to receive either placebo (n=7) or AM3 (n=7). The physical characteristics (mean+/-s) of the placebo group were as follows: age 25.7+/-2.1 years, body mass 87.2+/-4.1 kg, height 1.89+/-0.07 m, maximal oxygen uptake 65.3+/-4.2 ml.kg(-1).min(-1). Those of the AM3 group were as follows: age 26.1+/-1.9 years, body mass 85.8+/-6.1 kg, height 1.91+/-0.07 m, maximal oxygen uptake 64.6+/-4.5 ml.kg(-1).min(-1). All participants were evaluated for biochemical indices of muscle damage, including concentrations of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine kinase (CK) and its MB fraction (CK-MB), myoglobin, lactate dehydrogenase, urea, creatinine and gamma-glutamyltranspeptidase, both before and 30 days after treatment (over the peak of the competitive season). In the placebo group, competitive exercise (i.e. volleyball) was accompanied by significant increases in creatine kinase (494+/-51 to 560+/-53 IU.l(-1), P < 0.05) and myoglobin (76.8+/-2.9 to 83.9+/-3.1 microg.l(-1), P < 0.05); aspartate aminotransferase (30.8+/-3.0 to 31.1+/-2.9 IU.l(-1)) and lactate dehydrogenase (380+/-31 to 376+/-29 IU.l(-1)) were relatively unchanged after the 30 days maximum effort. AM3 not only inhibited these changes, it led to a decrease from baseline serum concentrations of creatine kinase (503+/-49 to 316+/-37 IU.l(-1), P < 0.05) and myoglobin (80.1+/-3.2 to 44.1+/-2.6 IU.l(-1), P < 0.05), as well as aspartate aminotransferase (31.1+/-3.3 to 26.1+/-2.7 IU.l(-1), P < 0.05) and lactate dehydrogenase (368+/-34 to 310+/-3 IU.l(-1), P < 0.05). The concentration of CK-MB was also significantly decreased from baseline with AM3 treatment (11.6+/-1.2 to 5.0+/-0.7 IU.l(-1), P < 0.05), but not with placebo (11.4+/-1.1 to 10.8+/-1.4 IU.l(-1)). In conclusion, the use of immunomodulators, such as AM3, by elite sportspersons during competition significantly reduces serum concentrations of proteins associated with muscle damage.  相似文献   

15.
The aim of this study was to determine the effect of carbohydrate (CHO) versus placebo (PLA) beverage consumption on the immune and plasma cortisol responses to a soccer-specific exercise protocol in 8 university team soccer players. In a randomized, counterbalanced design, the players received carbohydrate or placebo beverages before, during and after two 90 min soccer-specific exercise bouts (3 days apart) designed to mimic the activities performed and the distance covered in a typical soccer match. Blood and saliva samples were collected before, during and after the exercise protocol. Plasma lactate concentration increased to approximately 4 mmol x l(-1) at 45 and 90 min of exercise in both treatments (P<0.01). Plasma glucose concentration was significantly lower after 90 min of exercise with ingestion of the placebo than the carbohydrate (PLA: 4.57+/-0.12 mmol x l(-1); CHO: 5.49+/-0.11 mmol x l(-1); P<0.01). The pattern of change in plasma cortisol, circulating lymphocyte count and saliva immunoglobulin A secretion did not differ between the carbohydrate and placebo trials. Blood neutrophil counts were 14% higher 1 h after the placebo trial than the carbohydrate trial (PLA: 4.8+/-0.5x10(9) cells x l(-1); CHO: 4.2+/-0.5x10(9) cells x l(-1); P = 0.06), but the treatment had no effect on the degranulation response of blood neutrophils stimulated by bacterial lipopolysaccharide. We conclude that, although previous studies have shown that carbohydrate feeding is effective in attenuating immune responses to prolonged continuous strenuous exercise, the same cannot be said for a soccer-specific intermittent exercise protocol. When overall exercise intensity is moderate, and changes in plasma glucose, cortisol and immune variables are relatively small, it would appear that carbohydrate ingestion has only a minimal influence on the immune response to exercise.  相似文献   

16.
不同训练强度对间歇性缺氧大鼠骨骼肌NO和NOS的影响   总被引：6，自引：0，他引：6  
利用低氧舱技术模拟“高住低练”环境,观察间歇性缺氧条件和两种不同运动训练强度对骨骼肌NO和NOS的共同作用效应。SD雄性大鼠50只,随机分为6组:(1)常氧对照组(NC),(2)常氧低强度运动组(NEL),(3)常氧高强度运动组(NEH),(4)低氧对照组(HC),(5)低氧低强度运动组(HEL),(6)低氧高强度运动组(HEH)。低氧组每日20时至次日8时置于低氧舱中,其余时间置于常氧环境下。低氧舱氧浓度控制在14.7%,相当于海拔高度大约2800米。运动组每天在常氧环境中进行30分钟跑台训练,速度定为26.8米/分钟,低强度运动组坡度0度,高强度运动组坡度15度。9周后各组大鼠于安静状态进行宰杀,取股四头肌,匀浆进行NO含量和NOS活性检测。结果显示:常氧高强度运动组股四头肌NO水平与常氧对照组相比呈升高趋势并接近显著性水平(p=0.052)。低氧低运动强度组NO显著高于其他组,NOS变化组间比较均未达显著性水平。说明常氧条件下,高强度运动强度才能使NO释放增加。而在间歇性缺氧条件下,较低强度运动即可使NO释放明显增加。提示间歇性缺氧条件可使引起NO释放的运动强度阈值下降。  相似文献   

17.
The aim of this study was to devise a laboratory-based protocol for a motorized treadmill that was representative of work rates observed during soccer match-play. Selected physiological responses to this soccer-specific intermittent exercise protocol were then compared with steady-rate exercise performed at the same average speed. Seven male university soccer players (mean +/- s: age 24 +/- 2 years, height 1.78 +/- 0.1 m, mass 72.2 +/- 5.0 kg, VO2max 57.8 +/- 4 ml x kg(-1) x min(-1)) completed a 45-min soccer-specific intermittent exercise protocol on a motorized treadmill. They also completed a continuous steady-rate exercise session for an identical period at the same average speed. The physiological responses to the laboratory-based soccer-specific protocol were similar to values previously observed for soccer match-play (oxygen consumption approximately 68% of maximum, heart rate 168 +/- 10 beats x min(-1)). No significant differences were observed in oxygen consumption, heart rate, rectal temperature or sweat production rate between the two conditions. Average minute ventilation was greater (P < 0.05) in intermittent exercise (81.3 +/- 0.2 l x min(-1)) than steady-rate exercise (72.4 +/- 11.4 l x min(-1)). The rating of perceived exertion for the session as a whole was 15 +/- 2 during soccer-specific intermittent exercise and 12 +/- 1 for continuous exercise (P < 0.05). The physiological strain associated with the laboratory-based soccer-specific intermittent protocol was similar to that associated with 45 min of soccer match-play, based on the variables measured, indicating the relevance of the simulation as a model of match-play work rates. Soccer-specific intermittent exercise did not increase the demands placed on the aerobic energy systems compared to continuous exercise performed at the same average speed, although the results indicate that anaerobic energy provision is more important during intermittent than during continuous exercise at the same average speed.  相似文献   

18.
The aim of this study was to examine the effect of fatigue from maximal tennis hitting on skilled tennis performance. Eighteen senior county tennis players (9 males, 9 females) volunteered to participate in the study. Their mean ( - s x -macron ) age and body mass were as follows: males 20.7 - 0.9 years and 60.6 - 2.7 kg respectively, females 21.7 - 0.6 years and 71.5 - 1.8 kg respectively. The players undertook two performance tests, both against a tennis ball serving machine, on an indoor tennis surface: (1) a pre- and post-skill test of groundstrokes and service; (2) the Loughborough Intermittent Tennis Test (4 min work plus 40 s recovery) to volitional fatigue. Body mass decreased by 1.5% ( P ? 0.0001). Mean heart rates differed between rest, post-warm-up and all intermittent test values ( P ? 0.01), between the pre- and post-skill tests ( P ? 0.0001) and between bouts and recoveries ( P ? 0.01). Peak blood glucose and lactate concentrations were 5.9 mmol· l -1 (50% into the intermittent tennis test) and 9.6 - 0.9 mmol· l -1 (25% into the test) respectively. Mean time to volitional fatigue was 35.4 - 4.6 min. Groundstroke hitting accuracy decreased by 69% from start to volitional fatigue in the intermittent test ( P ? 0.01). Service accuracy to the right court declined by 30% after the intermittent tennis test. The results of this study suggest that fatigue was accompanied by a decline in some but not all tennis skills.  相似文献   

19.
Physiological correlates to off-road cycling performance   总被引：1，自引：1，他引：0  
The aim of this study was to examine the relationships between maximal and submaximal tests for aerobic fitness and performance in an off-road cross-country circuit race. Thirteen competitive off-road male cyclists participated in the study. Peak oxygen uptake (VO2peak), peak power output, and lactate thresholds corresponding to 1 mmol x l(-1) above baseline (lactate threshold) and to 4 mmol x l(-1) (onset of blood lactate accumulation) were measured during an incremental cycling test. Race time and final ranking within the same group of cyclists were determined during a cross-country off-road competition. All correlations between the measured parameters of aerobic fitness and off-road cycling performance were significant, particularly between race time and physiological parameters scaled to body mass0.79 (r = -0.68 to -0.94; P < 0.05) and between final ranking and physiological parameters expressed relative to body mass0.79 (r = -0.81 to - 0.96; P < 0.001). Moreover, there was a large difference (effect sizes = 1.12-1.70) in all measured parameters of aerobic fitness between the group of six cyclists with a race time above the median and the group of six cyclists with a race time below the median (P < 0.05). In conclusion, the results of this study provide empirical support to the widespread use of these maximal (VO2peak, peak power output) and submaximal (lactate thresholds) parameters of aerobic fitness in the physiological assessments of off-road cyclists. Furthermore, our results suggest body size should be taken into account when evaluating such athletes.  相似文献   

20.
Abstract

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 · kg?1) and in the control group (?0.13 ± 0.04 W · 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.  相似文献   

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