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1.
The aim of this study was to examine the effects of ingesting a carbohydrate‐electrolyte solution on endurance capacity during a prolonged intermittent, high‐intensity shuttle running test (PIHSRT). Nine trained male games players performed two exercise trials, 7 days apart. On each occasion, they completed 75 min exercise, comprising of five 15‐min periods of intermittent running, consisting of sprinting, interspersed with periods of jogging and walking (Part A), followed by intermittent running to fatigue (Part B). The subjects were randomly allocated either a 6.9% carbohydrate‐electrolyte solution (CHO) or a non‐carbohydrate placebo (CON) immediately prior to exercise (5 ml kg‐1 body mass) and every 15 min thereafter (2 ml kg‐1 body mass). Venous blood samples were obtained at rest, during and after each PIHSRT for the determination of glucose, lactate, plasma free fatty acid, glycerol, ammonia, and serum insulin and electrolyte concentrations. During Part B, the subjects were able to continue running longer when fed CHO (CHO = 8.9 ± 1.5 min vs CON = 6.7 ± 1.0 min; P < 0.05) (mean ± s.e.m.). These results show that drinking a carbohydrate‐electrolyte solution improves endurance running capacity during prolonged intermittent exercise.  相似文献   

2.
Objective: To quantify the effects of acute hypoxic exposure on exercise capacity and performance, which includes continuous and intermittent forms of exercise. Design: A systematic review was conducted with a three-level mixed effects meta-regression. The ratio of means method was used to evaluate main effects and moderators providing practical interpretations with percentage change. Data sources: A systemic search was performed using three databases (Google scholar, PubMed and SPORTDiscus). Eligibility criteria for selecting studies: Inclusion was restricted to investigations that assessed exercise performance (time trials (TTs), sprint and intermittent exercise tests) and capacity (time to exhaustion test, TTE) with acute hypoxic (<24?h) exposure and a normoxic comparator. Results: Eighty-two outcomes from 53 studies (N?=?798) were included in this review. The results show an overall reduction in exercise performance/capacity ?17.8?±?3.9% (95% CI ?22.8% to ?11.0%), which was significantly moderated by ?6.5?±?0.9% per 1000 m altitude elevation (95% CI ?8.2% to ?4.8%) and oxygen saturation (?2.0?±?0.4%; 95% CI ?2.9% to ?1.2%). TT (?16.2?±?4.3%; 95% CI ?22.9% to ?9%) and TTE (?44.5?±?6.9%; 95% CI ?51.3% to ?36.7%) elicited a negative effect, whilst indicating a quadratic relationship between hypoxic magnitude and both TTE and TT performance. Furthermore, exercise less than 2 min exhibited no ergolytic effect from acute hypoxia.

Summary/Conclusion: This review highlights the ergolytic effect of acute hypoxic exposure, which is curvilinear for TTE and TT performance with increasing hypoxic levels, but short duration intermittent and sprint exercise seem to be unaffected.  相似文献   

3.
The onset of exercise facilitates an improvement in psychomotor performance until the second ventilatory threshold, after which performance is reduced. This inverted-U relationship appears valid for incremental and steady-state exercise, however, not for intermittent exercise. This study examined changes in psychomotor performance of team sport officials during a laboratory-based match simulation. Twelve elite Australian football (n = 5) and rugby league (n = 7) officials (32.5 ± 5.5 years; 180.0 ± 6.8 cm; 78.8 ± 7.6 kg) completed the match simulation on a non-motorised treadmill. Physiological measures were routinely taken, while psychomotor performance was assessed using the Eriksen flanker task (multiple-choice response time). Significant reductions (P < 0.05) were observed in distance covered and high-speed running during the second half when compared to the first. No significant differences (P > 0.05) in psychomotor performance at different time points were observed. Response time was significantly improved when running above 65% of maximal sprinting speed (P < 0.01). This data questions the application of the inverted-U hypothesis for intermittent exercise and suggests that the short high-intensity efforts may not result in the same physiological events that limit psychomotor performance during sustained high-intensity exercise. More so, the high-intensity efforts during the match protocol appeared to promote psychomotor performance during the intermittent exercise.  相似文献   

4.
碳水化合物对高强度折返运动能力的影响   总被引：1，自引：0，他引：1  
运动对人体代谢的需要是代表一种营养上的挑战。营养能提供体内能量的再补充、生长、修复和水份的补充。运动期间能量代谢，碳水化合物扮演着重要的角色。虽然许多研究报告表明运动中补充碳水化合物可提高持续亚极限运动的耐力，但有些项目如足球、篮球等运动移位的方式，包括了高低速度折返跑和冲刺运动。本文研究的目的是了解碳水化合物对折返能力的影响  相似文献   

5.
Abstract

Exercise-induced oxidative stress is implicated in muscle damage and fatigue which has led athletes to embark on antioxidant supplementation regimes to negate these effects. This study investigated the intake of vitamin C (VC) (1 g), blackcurrant (BC) juice (15 mg VC, 300 mg anthocyanins) and placebo in isocaloric drink form on training progression, incremental running test and 5-km time-trial performance. Twenty-three trained female runners (age, 31±8 y; mean±SD) completed three blocks of high-intensity training for 3 wks and 3 days, separated by a washout (~3.7 wks). Changes in training and performance with each treatment were analysed with a mixed linear model, adjusting for performance at the beginning of each training block. Markers of oxidative status included protein carbonyl, malondialdehyde (in plasma and in vitro erythrocytes), ascorbic acid, uric acid and erythrocyte enzyme activity of superoxide dismutase, catalase and glutathione peroxidase were analysed. There was a likely harmful effect on mean running speed during training when taking VC (1.3%; 90% confidence limits ±1.3%). Effects of the two treatments relative to placebo on mean performance in the incremental test and time trial were unclear, but runners faster by 1 SD of peak speed demonstrated a possible improvement on peak running speed with BC juice (1.9%; ±2.5%). Following VC, certain oxidative markers were elevated: catalase at rest (23%; ±21%), protein carbonyls at rest (27%; ±38%) and superoxide dismutase post-exercise (8.3%; ±9.3%). In conclusion, athletes should be cautioned about taking VC chronically, however, BC may improve performance in the elite.  相似文献   

6.
Abstract

Studies have reported the benefits of pre-cooling prior to exercise in the heat for male athletes, but at this time no research has investigated female athletes. The aim of the following study was to test the effects of pre-cooling on female repeat sprint performance in hot, humid conditions; namely is ice ingestion effective in reducing core temperature (Tc) and does this reduced Tc lead to improved repeat sprint performance in female athletes? Nine female team sport athletes with mean age (21.0 ± 1.2 y), height (169.8 ± 4.1 cm) and body mass (62.3 ± 5.0 kg) participated in this study. Participants completed 72 min of an intermittent sprint protocol (ISP) consisting of 2 × 36 min halves in hot, humid conditions (33.1 ± 0.1°C, 60.3 ± 1.5% RH) on a cycle ergometer. This was preceded by 30 min of either ice ingestion (ICE) or water consumption (CON) in a randomised order. At the end of the pre-cooling period, Tc significantly decreased following ICE (?0.7 ± 0.3°C) compared to CON (?0.1 ± 0.2°C; p = 0.001). Tc also remained lower in ICE compared to CON during the ISP (p = 0.001). Ratings of perceived thermal sensation were lower in ICE compared to CON (p = 0.032) at the beginning (p = 0.022) and mid-point (p = 0.035) of the second half. No differences in work, mean power, peak power, rating of perceived exertion, heart rate or sweat loss between conditions were recorded (p > 0.05). Ice ingestion significantly reduced female Tc prior to intermittent exercise in the heat and reduced thermal sensation; however, this did not coincide with improved performance.  相似文献   

7.
We tested the hypothesis that work-matched supramaximal intermittent warm-up improves final-sprint power output to a greater degree than submaximal constant-intensity warm-up during the last 30?s of a 120-s supramaximal exercise simulating the final sprint during sports events lasting approximately 2?min. Ten male middle-distance runners performed a 120-s supramaximal cycling exercise consisting of 90?s of constant-workload cycling at a workload corresponding to 110% maximal oxygen uptake (VO2max) followed by 30?s of maximal-effort cycling. This exercise was preceded by 1) no warm-up (Control), 2) a constant-workload cycling warm-up at a workload of 60%VO2max for 6?min and 40?s, or 3) a supramaximal intermittent cycling warm-up for 6?min and 40?s consisting of 5 sets of 65?s of cycling at a workload of 46%VO2max?+?15?s of supramaximal cycling at a workload of 120%VO2max. By design, total work was matched between the two warm-up conditions. Supramaximal intermittent and submaximal constant-workload warm-ups similarly increased 5-s peak (590?±?191 vs. 604?±?215W, P?=?0.41) and 30-s mean (495?±?137 vs. 503?±?154W, P?=?0.48) power output during the final 30-s maximal-effort cycling as compared to the no warm-up condition (5-s peak: 471?±?165W; 30-s mean: 398?±?117W). VO2 during the 120-s supramaximal cycling was similarly increased by the two warm-ups as compared to no-warm up (P?≤?0.05). These findings show that work-matched supramaximal intermittent and submaximal constant-workload warm-ups improve final sprint (～30?s) performance to similar extents during the late stage of a 120-s supramaximal exercise bout.  相似文献   

8.
Abstract

The aim of this study was to include self-paced exercise within a modified Loughborough Intermittent Shuttle Test (LIST-P) in order to quantify key performance variables not possible with prescribed workloads. Sixteen male games players performed two trials of the LIST-P, at least 7 days apart. The LIST-P incorporates 4 × 15-min blocks of “prescribed-pace” activity (participants exercise in time to audible signals) followed by 2 × 15-min blocks of “self-paced” running (no audible signals). Distances covered and mean speeds were monitored during self-paced exercise. Total distance covered (12.54 ± 0.45 km vs. 12.64 ± 0.32 km; P = 0.10) and mean speed (8.37 ± 0.31 km ? h?1 vs. 8.44 ± 0.22 km ? h?1; P = 0.10) was similar between trials. Other indices also showed the test to be reliable (Pearson’s correlation = 0.89 and 0.90 (P < 0.01), total distance and mean speed, respectively; intraclass correlation coefficient = 0.88 and 0.88 (P < 0.01); standard error of measurement = ±0.13 km and ±0.09 km ? h?1; coefficient of variation (CV) = 1.7% and 1.7%; ratio limits of agreement = 1.00 */÷1.03 and 1.01 */÷1.04). Sprint time was also similar between trials (2.60 ± 0.19 s vs. 2.64 ± 0.23 s; P = 0.29). Incorporating self-paced exercise within an established intermittent shuttle running test appears to be a sensitive means of quantifying key performance variables for multiple-sprint sports research.  相似文献   

9.
The purpose of this study was to examine CHO ingestion on a cognitive task using a field-simulated time-trial (TT) under hypoxia in well-trained triathletes. Ten male triathletes (age: 22.1 ± 1.1 years; VO2max: 59.4 ± 1.4 ml/kg/min) participated in this double-blind/crossover/counter-balanced design study. Participants completed 3 TT trials: 1) normoxic placebo (NPLA; FiO2 = 20.9%), 2) hypoxic placebo (HPLA; FiO2 = 16.3%), and 3) hypoxic CHO (HCHO; 6% CHO provided as 2 ml/kg/15 min; FiO2 = 16.3%). During the TT, physiological responses (SpO2, HR, RPE, and blood glucose/lactate), cognitive performance, and cerebral haemodynamics were measured. Hypoxia reduced TT performance by ~3.5–4% (p < 0.05), but CHO did not affect TT performance under hypoxia. For the cognitive task, CHO slightly preserved exercise-induced cognitive reaction speed but did not affect response accuracy during hypoxic exercise. However, CHO did not preserve the decreased Hb-Diff (cerebral blood flow, CBF) and increased HHb in the prefrontal lobe (p < 0.05) during hypoxic exercise, and CHO failed to preserve hypoxia-suppressed prefrontal CBF and tissue oxygen saturation. In conclusion, the present study demonstrates that CHO is effective in sustaining reaction speed for a cognitive task but not promoting TT performance during hypoxic exercise, which would be important for strategy-/decision-making when athletes compete at moderate high-altitude.  相似文献   

10.
This study investigated the relationship between several measures of lower-body stiffness and physical performance variables in 22 sub-elite male football players (mean ± SD; 21.9 ± 1.5 yr; 1.79 ± 0.06 m; 72.2 ± 7.2 kg). The participants were assessed for individual muscle stiffness of the Rectus Femoris (RF), Biceps Femoris (BF) and Medial Gastrocnemius (MG) muscles and vertical stiffness (Kvert) was also assessed assessed running acceleration, maximal sprint speed, agility, vertical jumping and muscular strength. Pearson’s correlations quantified the relationships and participants were also separated into relatively stiff (SG) and compliant groups (CG) for each variable. When ranked by Kvert the SG exhibited superior performance during sprinting, agility, jumping and strength (p ≤ 0.05) and when ranked by RF stiffness, SG exhibited superior sprint, agility and drop jump performance (p ≤ 0.05), while MG and BF stiffness were not related to performance. Higher stiffness appears to be beneficial to athletic performance for football players and therefore it may be beneficial for practitioners working with athletes that are required to perform dynamic activities to consider the contribution of stiffness to athletic performance.  相似文献   

11.
PurposeThe purpose of this study was to compare the effects of intermittent sprint training and plyometric training on endurance running performance.MethodsFourteen moderately trained male endurance runners were allocated into either the intermittent sprint training group (n = 7) or the plyometric training group (n = 7). The preliminary tests required subjects to perform a treadmill graded exercise test, a countermovement jump test for peak power measurement, and a 10-km time trial. Training included 12 sessions of either intermittent sprint or plyometric training carried out twice per week. On completion of the intervention, post-tests were conducted.ResultsBoth groups showed significant reduction in weekly training mileage from pre-intervention during the intervention period. There were significant improvements in the 10-km time trial performance and peak power. There was also significant improvement in relative peak power for both groups. The 10-km time trial performance and relative peak power showed a moderate inverse correlation.ConclusionThese findings showed that both intermittent sprint and plyometric training resulted in improved 10-km running performance despite reduction in training mileage. The improvement in running performance was accompanied by an improvement in peak power and showed an inverse relationship with relative peak power.  相似文献   

12.
The aim of this study was to assess the effect of the recovery duration in intermittent training drills on metabolism and coordination in sport games. Ten nationally ranked male tennis players (age 25.3±3.7 years, height 1.83±0.8 m, body mass 77.8±7.7 kg; mean ±s x ) participated in a passing-shot drill (baseline sprint with subsequent passing shot) that aimed to improve both starting speed and stroke quality (speed and precision). Time pressure for stroke preparation was individually adjusted by a ball-machine and corresponded to 80% of maximum running speed. In two trials (T10, T15) separated by 2 weeks, the players completed 30 strokes and sprints subdivided into 6 2 5 repetitions with a 1 min rest between series. The rest between each stroke-and-sprint lasted either 10 s (T10) or 15 s (T15). The sequence of both conditions was randomized between participants. Post-exercise blood lactate concentration was significantly elevated in T10 (9.04±3.06 vs 5.01±1.35 mmol·l-1, P ? 0.01). Running time for stroke preparation (1.405±0.044 vs 1.376±0.045 s, P ? 0.05) and stroke speed (106±12 vs 114±8 km·h-1, P ? 0.05) were significantly decreased in T10, while stroke precision - that is, more target hits ( P ? 0.1) and fewer errors (P ? 0.05) - tended to be higher. We conclude that running speed and stroke quality during intermittent tennis drills are highly dependent on the duration of recovery time. Optimization of training efficacy in sport games (e.g. combined improvement of conditional and technical skills) requires skilful fine-tuning of monitoring guidelines.  相似文献   

13.
目的:观察补充活性肽对大鼠骨骼肌细胞结蛋白和波形蛋白免疫染色和血清酶活性的影响,研究活性肽对运动性骨骼肌微结构损伤的保护作用。方法:雄性SD大鼠100只,依分别补充安慰剂和活性肽,运动与不运动,以及运动后0h、12h、24h和48h等不同时间随机分为10组,所有动物膳食平衡1周后,进行实验。运动组大鼠以(20±1)m/min的速度,坡度为-16,°持续性跑台训练120min。实验组和对照组所有动物在膳食平衡期间每天分别进行灌胃15%活性肽饮料2mL和等量的安慰剂。结果:补充活性肽可减轻大鼠离心运动后骨骼肌结蛋白免疫染色的丢失,增强波形蛋白的免疫染色,明显减少血清酶CK、LDH的漏出。  相似文献   

14.
Abstract

The effect of intermittent hypoxia on sea-level endurance performance was assessed by using hypoxic tents to simulate the live high-train low approach to altitude training. Eleven male sub-elite competitive runners and triathletes participated in a crossover study of usual training (control) and usual training with altitude exposure (altitude). Altitude treatment consisted of 25±3?d (mean±SD) of sleeping in tents for 8.1±0.6?h.d?1, progressing from a simulated altitude of 2500?m to 3500?m above sea level. Washout period between control and altitude treatments was 4?wk. Three treadmill runs to exhaustion lasting ～2, ～4 and ～8?min were completed 7 and 12?d after control and altitude treatments. Times for standard competition distances (800, 1500 and 3000?m), were predicted using a log-log model, improved by 1.0% (90% confidence limits, ±1.3%), 1.4% (±1.2%) and 1.9% (±1.5%), respectively. Improvements were greater in the six athletes with an I allele for angiotensin converting enzyme (ACE): 2.3% (±1.5%), 2.2% (±1.5%), and 2.1%, (±2.1%), respectively. Effects of simulated altitude on hemoglobin concentration were unclear. Altitude exposure simulated with hypoxic tents is likely to enhance performance substantially in middle-distance endurance running events, especially for individuals with an I allele of the ACE gene.  相似文献   

15.
This study examined the effects of different work?–?rest durations during 40?min intermittent treadmill exercise and subsequent running performance. Eight males (mean?±?s: age 24.3?±?2.0 years, body mass 79.4?±?7.0?kg, height 1.77?±?0.05?m) undertook intermittent exercise involving repeated sprints at 120% of the speed at which maximal oxygen uptake (v-[Vdot]O2max) was attained with passive recovery between each one. The work?–?rest ratio was constant at 1:1.5 with trials involving short (6:9?s), medium (12:18?s) or long (24:36?s) work?–?rest durations. Each trial was followed by a performance run to volitional exhaustion at 150% v-[Vdot]O2max. After 40?min, mean exercise intensity was greater during the long (68.4?±?9.3%) than the short work?–?rest trial (54.9?±?8.1% [Vdot]O2max; P?<?0.05). Blood lactate concentration at 10?min was higher in the long and medium than in the short work?–?rest trial (6.1?±?0.8, 5.2?±?0.9, 4.5?±?1.3?mmol?·?l?1, respectively; P?<?0.05). The respiratory exchange ratio was consistently higher during the long than during the medium and short work?–?rest trials (P <?0.05). Plasma glucose concentration was higher in the long and medium than in the short work?–?rest trial after 40?min of exercise (5.6?±?0.1, 6.6?±?0.2 and 5.3?±?0.5?mmol?·?l?1, respectively; P?<?0.05). No differences were observed between trials for performance time (72.7?±?14.9, 63.2?±?13.2, 57.6?±?13.5?s for the short, medium and long work?–?rest trial, respectively; P = 0.17), although a relationship between performance time and 40?min plasma glucose was observed (P?<?0.05). The results show that 40?min of intermittent exercise involving long and medium work?–?rest durations elicits greater physiological strain and carbohydrate utilization than the same amount of intermittent exercise undertaken with a short work?–?rest duration.  相似文献   

16.
Abstract

This study examined the effects of a 6-week intermittent exercise training, at different intensities, on body composition, functional walking and aerobic endurance in overweight children. Forty-eight overweight children (age: 10.4 ± 0.9 years) were randomly assigned to either intervention or control group. Lower and higher intensity intermittent exercise groups (LIIE and HIIE) performed intermittent running three times a week. LIIE performed more intervals at a lower intensity [16 intervals at 100% of individual maximal aerobic speed (MAS), 8 minutes in total], and HIIE performed fewer intervals at a higher intensity (12 intervals at 120% of MAS, 6 minutes in total). Each interval consisted of a 15-second run at the required speed, followed by a 15-second passive recovery. After 6 weeks, HIIE had a significantly (p < 0.05) higher percentage reduction in sum of skinfolds (i.e. calf and triceps), and significantly (p < 0.05) fewer steps during the functional obstacle performance, as compared with LIIE and control group. Significant improvement (p < 0.05) was found in intermittent aerobic endurance for HIIE as compared to the control group. Higher intensity intermittent training is an effective and time-efficient intervention for improving body composition, functional walking and aerobic endurance in overweight children.  相似文献   

17.
It has previously been shown that the metabolic acidaemia induced by a continuous warm-up at the 'lactate threshold' is associated with a reduced accumulated oxygen deficit and decreased supramaximal performance. The aim of this study was to determine if an intermittent, high-intensity warm-up could increase oxygen uptake (V02) without reducing the accumulated oxygen deficit, and thus improve supramaximal performance. Seven male 500 m kayak paddlers, who had represented their state, volunteered for this study. Each performed a graded exercise test to determine V02max and threshold parameters. On subsequent days and in a random, counterbalanced order, the participants then performed a continuous or intermittent, high-intensity warm-up followed by a 2 min, all-out kayak ergometer test. The continuous warm-up consisted of 15 min of exercise at approximately 65% V02max. The intermittent, high-intensity warm-up was similar, except that the last 5 min was replaced with five 10 s sprints at 200% V02max, separated by 50 s of recovery at ~55% V02max. Significantly greater (P<0.05) peak power (intermittent vs continuous: 629 ± 199 vs 601 ± 204W) and average power (intermittent vs continuous: 328±39.0 vs 321 ±42.4 W) were recorded after the intermittent warm-up. There was no significant difference between conditions for peak V02, total V02 or the accumulated oxygen deficit. The results of this study indicate that 2 min all-out kayak ergometer performance is significantly better after an intermittent rather than a continuous warm-up.  相似文献   

18.
This investigation assessed whether prior heavy resistance exercise would improve the repeated sprint performance of 16 trained youth soccer players (Age 17.05 ± 0.65 years; height 182.6 ± 8.9 cm; body mass 77.8 ± 8.2 kg). In session 1, individual 1 repetition max was measured utilising a squat movement. In sessions 2 and 3, participants performed a running-based repeated anaerobic sprint test with and without prior heavy resistance exercise of 91% of their 1 repetition max. Times were recorded for each of the 6 sprints performed in the repeated sprint test and summed to provide total time. T-tests compared the two exercise conditions via differences in corresponding sprint times and total time. Analysis revealed significantly reduced total time with use of heavy resistance exercise (33.48 (±1.27) vs. 33.59 (±1.27); P = 0.01). Sprints 1 (P = 0.05) and 2 (P = 0.02) were also faster in the heavy resistance exercise condition (5.09 (±0.16) vs. 5.11 (±0.16) and 5.36 (±0.24) vs. 5.45 (±0.26) seconds respectively) although no other differences were shown. Findings demonstrate improved sprint times of trained adolescent soccer players after heavy resistance exercise although benefits appear not as sustained as in adult participants.  相似文献   

19.
In this study we examined the performance during, and the physiological and metabolic responses to, prolonged, intermittent, high-intensity shuttle running in hot (～30 C, dry bulb temperature) and moderate (～20 C) environmental conditions. Twelve male students, whose mean (s x ) age, body mass and maximal oxygen uptake (V O 2m ax ) were 22 ± 1 years, 69.8 ± 01.8 kg and 56.9 ± 1.1 ml . kg ?1 . min ?1 respectively, performed intermittent high- and low-speed running involving five sets of ～15 min of repeated cycles of walking and variable speed running followed by 60 s run/rest exercise until fatigue. The total distance completed in the hot and moderate trials was 8842 3790 m and 11,280 214 m respectively (P < 0.01). This decrement in performance occurred even though no differences existed in the level of dehydration, rating of perceived exertion, blood glucose and lactate, plasma free fatty acid and ammonia concentrations between the two trials. However, water consumption was almost twice as great in the hot trial (hot vs moderate: 1.18 ± 0.12 vs 0.63 ± 0.07 l . h ?1 , P < 0.01). Rectal temperature (hot vs moderate: 39.4 ± 0.1 vs 38.0 ± 0.1 C, P < 0.01) and heart rate (hot vs moderate: 186 ± 2 vs 179 ± 2 beats . min ?1 , P < 0.05) were higher at the end of the hot condition than at the same point in time in the moderate condition. The correlation between the rate of rise in rectal temperature and the distance completed during the hot condition was -0.94 (P < 0.01); for the moderate condition it was -0.65 (P <0.05). The reduced performance in the hot condition was associated with high body temperature; the precise mechanisms by which the performance decrement was brought about are, however, unclear.  相似文献   

20.
This investigation reports the effects of chewing caffeinated gum on race performance with trained cyclists. Twenty competitive cyclists completed two 30-km time trials that included a maximal effort 0.2-km sprint each 10-km. Caffeine (~3–4 mg · kg?1) or placebo was administered double-blind via chewing gum at the 10-km point following completion of the first sprint. Measures of power output, oxygen uptake, heart rate, lactate and perceived exertion were taken at set intervals during the time trial. Results indicated no substantial differences in any measured variables between caffeine and placebo conditions during the first 20-km of the time trial. Caffeine gum did however lead to substantial enhancements (mean ± 90% confidence limits (CLs)) in mean power during the final 10-km (3.8% ± 2.3%), and sprint power at 30-km (4.0% ± 3.6%). The increases in performance over the final 10-km were associated with small increases in heart rate and blood lactate (effect size of 0.24 and 0.28, respectively). There were large inter-individual variations in the response to caffeine, and apparent gender related differences in sprint performance. Chewing caffeine gum improves mean and sprint performance power in the final 10-km of a 30-km time trial in male and female cyclists most likely through an increase in nervous system activation.  相似文献   

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