共查询到20条相似文献，搜索用时 417 毫秒
1.
Marc J. Quod David T. Martin Andrew S. Gardner Shona L. Halson Frank E. Marino 《Journal of sports sciences》2013,31(14):1477-1487
Abstract The purpose of this study was to compare the effects of two practical precooling techniques (skin cooling vs. skin + core cooling) on cycling time trial performance in warm conditions. Six trained cyclists completed one maximal graded exercise test ([Vdot]O2peak 71.4 ± 3.2 ml · kg?1 · min?1) and four ～40 min laboratory cycling time trials in a heat chamber (34.3°C ± 1.1°C; 41.2% ± 3.0% rh) using a fixed-power/variable-power format. Cyclists prepared for the time trial using three techniques administered in a randomised order prior to the warm-up: (1) no cooling (control), (2) cooling jacket for 40 min (jacket) or (3) 30-min water immersion followed by a cooling jacket application for 40 min (combined). Rectal temperature prior to the time trial was 37.8°C ± 0.1°C in control, similar in jacket (37.8°C ± 0.3°C) and lower in combined (37.1°C ± 0.2°C, P < 0.01). Compared with the control trial, time trial performance was not different for jacket precooling (?16 ± 36 s, ?0.7%; P = 0.35) but was faster for combined precooling (?42 ± 25 s, ?1.8%; P = 0.009). In conclusion, a practical combined precooling strategy that involves immersion in cool water followed by the use of a cooling jacket can produce decrease in rectal temperature that persist throughout a warm-up and improve laboratory cycling time trial performance in warm conditions. 相似文献
2.
The aim of this study was to determine the influence of type of warm-up on metabolism and performance during high-intensity exercise. Eight males performed 30 s of intense exercise at 120% of their maximal power output followed, 1 min later, by a performance cycle to exhaustion, again at 120% of maximal power output. Exercise was preceded by active, passive or no warm-up (control). Muscle temperature, immediately before exercise, was significantly elevated after active and passive warm-ups compared to the control condition (36.9 +/- 0.18 degrees C, 36.8 +/- 0.18 degrees C and 33.6 +/- 0.25 degrees C respectively; mean +/- sx) (P< 0.05). Total oxygen consumption during the 30 s exercise bout was significantly greater in the active and passive warm-up trials than in the control trial (1017 +/- 22, 943 +/- 53 and 838 +/- 45 ml O2 respectively). Active warm-up resulted in a blunted blood lactate response during high-intensity exercise compared to the passive and control trials (change = 5.53 +/- 0.52, 8.09 +/- 0.57 and 7.90 +/- 0.38 mmol x l(-1) respectively) (P < 0.05). There was no difference in exercise time to exhaustion between the active, passive and control trials (43.9 +/- 4.1, 48.3 +/- 2.7 and 46.9 +/- 6.2 s respectively) (P= 0.69). These results indicate that, although the mechanism by which muscle temperature is elevated influences certain metabolic responses during subsequent high-intensity exercise, cycling performance is not significantly affected. 相似文献
3.
Whole-body pre-cooling and heat storage during self-paced cycling performance in warm humid conditions 总被引：1，自引：1，他引：0
The aim of this study was to establish the effect that pre-cooling the skin without a concomitant reduction in core temperature has on subsequent self-paced cycling performance under warm humid (31 degrees C and 60% relative humidity) conditions. Seven moderately trained males performed a 30 min self-paced cycling trial on two separate occasions. The conditions were counterbalanced as control or whole-body pre-cooling by water immersion so that resting skin temperature was reduced by approximately 5-6 degrees C. After pre-cooling, mean skin temperature was lower throughout exercise and rectal temperature was lower (P < 0.05) between 15 and 25 min of exercise. Consequently, heat storage increased (P < 0.003) from 84.0+/-8.8 W x m(-2) to 153+/-13.1 W x m(-2) (mean +/- s(mean)) after pre-cooling, while total body sweat fell from 1.7+/-0.1 l x h(-1) to 1.2+/-0.1 l h(-1) (P < 0.05). The distance cycled increased from 14.9+/-0.8 to 15.8+/-0.7 km (P < 0.05) after pre-cooling. The results indicate that skin pre-cooling in the absence of a reduced rectal temperature is effective in reducing thermal strain and increasing the distance cycled in 30 min under warm humid conditions. 相似文献
4.
To assess the effect of cold water immersion and active recovery on thermoregulation and repeat cycling performance in the heat, ten well-trained male cyclists completed five trials, each separated by one week. Each trial consisted of a 30-min exercise task, one of five 15-min recoveries (intermittent cold water immersion in 10 degrees C, 15 degrees C and 20 degrees C water, continuous cold water immersion in 20 degrees C water or active recovery), followed by 40 min passive recovery, before repeating the 30-min exercise task. Recovery strategy effectiveness was assessed via changes in total work in the second exercise task compared with that in the first. Following active recovery, a mean 4.1% (s = 1.8) less total work (P = 0.00) was completed in the second than in the first exercise task. However, no significant differences in total work were observed between any of the cold water immersion protocols. Core and skin temperature, blood lactate concentration, heart rate, rating of thermal sensation, and rating of perceived exertion were recorded. During both exercise tasks there were no significant differences in blood lactate concentration between interventions; however, following active recovery blood lactate concentration was significantly lower (P < 0.05; 2.0 +/- 0.8 mmol . l(-1)) compared with all cold water immersion protocols. All cold water immersion protocols were effective in reducing thermal strain and were more effective in maintaining subsequent high-intensity cycling performance than active recovery. 相似文献
5.
Diurnal variation in cycling performance: influence of warm-up 总被引：2，自引：0，他引：2
We examined the effects of time of day on a cycling time trial with and without a prolonged warm-up, among cyclists who tended towards being high in "morningness". Eight male cyclists (mean +/- s: age = 24.9 +/- 3.5 years, peak power output = 319 +/- 34 W, chronotype = 39 +/- 6 units) completed a 16.1-km time trial without a substantial warm-up at both 07:30 and 17:30 h. The time trial was also completed at both times of day after a 25-min warm-up at 60% of peak power. Power output, heart rate, intra-aural temperature and category ratings of perceived exertion (CR-10) were measured throughout the time trial. Post-test blood lactate concentration was also recorded. Warm-up generally improved time trial performance at both times of day (95% CI for improvement = 0 to 30 s), but mean cycling time was still significantly slower at 07:30 h than at 17:30 h after the warm-up (95% CI for difference = 33 to 66 s). Intra-aural temperature increased as the time trial progressed (P < 0.0005) and was significantly higher throughout the time trials at 17:30 h (P = 0.001), irrespective of whether the cyclists performed a warm-up or not. Blood lactate concentration after the time trial was lowest at 07:30 h without a warm-up (P = 0.02). No effects of time of day or warm-up were found for CR-10 or heart rate responses during the time trial. These results suggest that 16.1-km cycling performance is worse in the morning than in the afternoon, even with athletes who tend towards 'morningness', and who perform a vigorous 25-min warm-up. Diurnal variation in cycling performance is, therefore, relatively robust to some external and behavioural factors. 相似文献
6.
The thermoregulatory responses of upper-body trained athletes were examined at rest, during prolonged arm crank exercise and recovery in cool (21.5 +/- 0.9 degrees C, 43.9 +/- 10.1% relative humidity; mean +/- s) and warm (31.5 +/- 0.6 degrees C, 48.9 +/- 8.4% relative humidity) conditions. Aural temperature increased from rest by 0.7 +/- 0.7 degrees C (P< 0.05) during exercise in cool conditions and by 1.6 +/- 0.7 degrees C during exercise in warm conditions (P< 0.05). During exercise in cool conditions, calf skin temperature decreased (1.5 +/- 1.3 degrees C), whereas an increase was observed during exercise in warm conditions (3.0 +/- 1.7 degrees C). Lower-body skin temperatures tended to increase by greater amounts than upper-body skin temperatures during exercise in warm conditions. No differences were observed in blood lactate, heart rate or respiratory exchange ratio responses between conditions. Perceived exertion at 45 min of exercise was greater than that reported at 5 min of exercise during the cool trial (P< 0.05), whereas during exercise in the warm trial the rating of perceived exertion increased from initial values by 30 min (P < 0.05). Heat storage, body mass losses and fluid consumption were greater during exercise in warm conditions (7.06 +/- 2.25 J x g(-1) x degrees C(-1), 1.3 +/- 0.5 kg and 1,038 +/- 356 ml, respectively) than in cool conditions (1.35 +/- 0.23 J x g(-1) x degrees C(-1), 0.8 +/- 0.2 kg and 530 +/- 284 ml, respectively; P < 0.05). The results of this study indicate that the increasing thermal strain with constant thermal stress in warm conditions is due to heat storage within the lower body. These results may aid in understanding thermoregulatory control mechanisms of populations with a thermoregulatory dysfunction, such as those with spinal cord injuries. 相似文献
7.
Sweat lactate reflects eccrine gland metabolism. However, the metabolic tendencies of eccrine glands in a hot versus thermoneutral environment are not well understood. Sixteen male volunteers completed a maximal cycling trial and two 60-min cycling trials [30 degrees C = 30 +/- 1 degrees C and 18 degrees C = 18 +/- 1 degrees C wet bulb globe temperature (WBGT)]. The participants were requested to maintain a cadence of 60 rev min(-1) with the intensity individualized at approximately 90% of the ventilatory threshold. Sweat samples at 10, 20, 30, 40, 50 and 60 min were analysed for lactate concentration. Sweat rate at 30 degrees C (1380 +/- 325 ml x h(-1)) was significantly greater (P < 0.05) than at 18 degrees C (632 +/- 311 ml x h(-1)). Sweat lactate concentration was significantly greater (P < 0.05) at each time point during the 18 degrees C trial, with values between trials tending to converge across time. During the 30 degrees C trial, both heart rate (20, 30, 40, 50 and 60 min) and rectal temperature (30, 40, 50 and 60 min) were significantly higher than in the 18 degrees C trial. Higher sweat lactate concentrations coupled with lower sweat rates may indicate a greater relative contribution of oxygen-independent metabolism within eccrine glands during exercise at 18 degrees C. Decreases in sweat lactate concentration across time suggest either greater dilution due to greater sweat volume or increased reliance on aerobic metabolism within eccrine glands. The convergence of lactate concentrations between trials may indicate that time-dependent modifications in sweat gland metabolism occur at different rates contingent partially on environmental conditions. 相似文献
8.
The aim of this study was to assess the effect of time of day on physiological responses to running at the speed at the lactate threshold. After determination of the lactate threshold, using a standard incremental protocol, nine male runners (age 26.3 +/- 5.7 years, height 1.77 +/- 0.07 m, mass 73.1 +/- 6.5 kg, lactate threshold speed 13.6 +/- 1.6 km x h(-1); mean +/- s) completed a standardized 30 min run at lactate threshold speed, twice within 24 h (07:00-09:00 h and 18:00-21:00 h). Core body temperature, heart rate, minute ventilation, oxygen uptake, carbon dioxide expired, respiratory exchange ratio and capillary blood lactate were measured at rest, after a warm-up and at 10, 20 and 30 min during the run. In addition, the rating of perceived exertion was reported every 10 min during the run. Significant diurnal variation was observed only for body temperature (36.9 +/- 0.9 degrees C vs 37.3 +/- 0.3 degrees C) and respiratory exchange ratio at rest (0.86 +/- 0.01 vs 0.89 +/- 0.07) (P < 0.05). Diurnal variation persisted for body temperature throughout the warm-up (37.1 +/- 0.2 degrees C vs 37.5 +/- 0.3 degrees C) and during exercise (36.2 +/- 0.6 degrees C vs 38.6 +/- 0.4 degrees C), but only during the warm-up for the respiratory exchange ratio (0.85 +/- 0.05 vs 0.87 +/- 0.02) (P < 0.05). The rating of perceived exertion was significantly elevated during the morning trial (12.7 +/- 0.9 vs 11.9 +/- 1.2) (P < 0.05). These findings suggest that, despite the diurnal variation in body temperature, other physiological responses to running at lactate threshold speed are largely unaffected. However, a longer warm-up may be required in morning trials because of a slower increase in body temperature, which could have an impact on ventilation responses and ratings of perceived exertion. 相似文献
9.
It is perceived that, during the triathlon or duathlon, cycling with a steep (> 76 degrees) rather than a shallow (< 76 degrees ) frame geometry might attenuate the fatigue associated with progression from the cycle to run disciplines and improve subsequent 10-km running performance. This is based on anecdotal testimony from athletes purporting to have experienced improved performance; no empirical evidence exists. To evaluate this view, eight male triathletes completed a counterbalanced, 40-km cycle ride at two frame geometries (73 degrees and 81 degrees) at approximately 70% VO2peak. Immediately after completion of each 40-km cycle, a self-paced 10-km treadmill time trial was undertaken, during which physiological, kinematic and performance variables were measured. The 10-km run performance (mean +/- s: 42:55 +/- 4:19 vs 46:15 +/- 4:52 min; P< 0.01) and combined cycle and run performance (1:45:49 +/- 5:45 vs 1:50:33 +/- 6:08; P< 0.001) were faster in the 81 degrees than the 73 degrees condition. Improvements in performance were most prominent during the first 5 km of the run (21:41 +/- 2:15 vs 24:15 +/- 2:31 min in the 81 degrees and 73 degrees conditions respectively). These improvements were not evident during the second 5 km of the run. No differences in physiological variables were noted, although heart rate, stride length and stride frequency were increased during the 81 degrees condition (P < 0.05). Modifying frame geometry from a seat tube angle of 73 degrees to 81 degrees improves 10-km running and combined cycle plus run performance. These improvements in performance might relate to alterations during the cycling phase, which minimizes the 'residual effect' of this (i.e. the adverse changes in substrate availability, thermoregulatory, cardiovascular and biomechanical factors felt immediately after transition from cycling to running) and attenuates negative changes in physiological and kinematic responses during the 10-km run. 相似文献
10.
Nine males cycled at 53% (s = 2) of their peak oxygen uptake (VO(2peak)) for 90 min (dry bulb temperature: 25.4 degrees C, s = 0.2; relative humidity: 61%, s = 3). One litre of flavoured water at 10 (cold), 37 (warm) or 50 degrees C (hot) was ingested 30 - 40 min into exercise. Immediately after the 90 min of exercise, participants cycled at 95%VO(2peak) to exhaustion to assess exercise capacity. Rectal and mean skin temperatures and heart rate were recorded. The gradient of rise in rectal temperature was influenced (P < 0.01) by drink temperature. Mean skin temperature was highest in the hot trial (cold trial: 34.2 degrees C, s = 0.5; warm trial: 34.4 degrees C, s = 0.5; hot trial: 34.7 degrees C, s = 0.6; P < 0.01). Significant differences were observed in heart rate (cold trial: 132 beats . min(-1), s = 13; warm trial: 134 beats . min(-1), s = 12; hot trial: 139 beats . min(-1), s = 13; P < 0.05). Exercise capacity was similar between trials (cold trial: 234 s, s = 69; warm trial: 214 s, s = 52; hot trial: 203 s, s = 53; P = 0.562). The heat load and debt induced via drinking resulted in appropriate thermoregulatory reflexes during exercise leading to an observed heat content difference of only 33 kJ instead of the predicted 167 kJ between the cold and hot trials. These results suggest that there may be a role for drink temperature in influencing thermoregulation during exercise. 相似文献
11.
Nine male student games players consumed either flavoured water (0.1 g carbohydrate, Na+ 6 mmol x l(-1)), a solution containing 6.5% carbohydrate-electrolytes (6.5 g carbohydrate, Na+ 21 mmol x l(-1)) or a taste placebo (Na+ 2 mmol x l(-1)) during an intermittent shuttle test performed on three separate occasions at an ambient temperature of 30 degrees C (dry bulb). The test involved five 15-min sets of repeated cycles of walking and variable speed running, each separated by a 4-min rest (part A of the test), followed by 60 s run/60 s rest until exhaustion (part B of the test). The participants drank 6.5 ml x kg(-1) of fluid as a bolus just before exercise and thereafter 4.5 ml x kg(-1) during every exercise set and rest period (19 min). There was a trial order effect. The total distance completed by the participants was greater in trial 3 (8441 +/- 873 m) than in trial 1 (6839 +/- 512, P < 0.05). This represented a 19% improvement in exercise capacity. However, the trials were performed in a random counterbalanced order and the participants completed 8634 +/- 653 m, 7786 +/- 741 m and 7099 +/- 647 m in the flavoured water (FW), placebo (P) and carbohydrate-electrolyte (CE) trials, respectively (P = 0.08). Sprint performance was not different between the trials but was impaired over time (FW vs P vs CE: set 1, 2.41 +/- 0.02 vs 2.39 +/- 0.03 vs 2.39 +/- 0.03 s; end set, 2.46 +/- 0.03 vs 2.47 +/- 0.03 vs 2.47 +/- 0.02 s; main effect time, P < 0.01). The rate of rise in rectal temperature was greater in the carbohydrate-electrolyte trial (rise in rectal temperature/duration of trial, degrees C x h(-1); FW vs CE, P < 0.05; P vs CE, N.S.). Blood glucose concentrations were higher in the carbohydrate-electrolyte than in the other two trials (FW vs P vs CE:rest, 4.4 +/- 0.1 vs 4.3 +/- 0.1 vs 4.2 +/- 0.1 mmol x l(-1); end of exercise, 5.4 +/- 0.3 vs 6.4 +/- 0.6 vs 7.2 +/- 0.5 mmol x l(-1); main effect trial, P < 0.05; main effect time, P < 0.01). Plasma free fatty acid concentrations at the end of exercise were lower in the carbohydrate-electrolyte trial than in the other two trials (FW vs P vs CE: 0.57 +/- 0.08 vs 0.53 +/- 0.11 vs 0.29 +/- 0.04 mmol x l(-1); interaction, P < 0.01). The correlation between the rate of rise in rectal temperature (degrees C x h(-1)) and the distance completed was -0.91, -0.92 and -0.96 in the flavoured water, placebo and carbohydrate-electrolyte conditions, respectively (P < 0.01). Heart rate, blood pressure, plasma ammonia, blood lactate, plasma volume and rate of perceived exertion were not different between the three fluid trials. Although drinking the carbohydrate-electrolyte solution induced greater metabolic changes than the flavoured water and placebo solutions, it is unlikely that in these unacclimated males carbohydrate availability was a limiting factor in the performance of intermittent running in hot environmental conditions. 相似文献
12.
Greg Atkinson Clare Todd Thomas Reilly James Waterhouse 《Journal of sports sciences》2013,31(3):321-329
We examined the effects of time of day on a cycling time trial with and without a prolonged warm-up, among cyclists who tended towards being high in “morningness”. Eight male cyclists (mean?±?s: age = 24.9?±?3.5 years, peak power output = 319?±?34?W, chronotype = 39?±?6 units) completed a 16.1-km time trial without a substantial warm-up at both 07:30 and 17:30?h. The time trial was also completed at both times of day after a 25-min warm-up at 60% of peak power. Power output, heart rate, intra-aural temperature and category ratings of perceived exertion (CR-10) were measured throughout the time trial. Post-test blood lactate concentration was also recorded. Warm-up generally improved time trial performance at both times of day (95% CI for improvement = 0 to 30?s), but mean cycling time was still significantly slower at 07:30?h than at 17:30?h after the warm-up (95% CI for difference = 33 to 66?s). Intra-aural temperature increased as the time trial progressed (P <?0.0005) and was significantly higher throughout the time trials at 17:30?h (P = 0.001), irrespective of whether the cyclists performed a warm-up or not. Blood lactate concentration after the time trial was lowest at 07:30?h without a warm-up (P = 0.02). No effects of time of day or warm-up were found for CR-10 or heart rate responses during the time trial. These results suggest that 16.1-km cycling performance is worse in the morning than in the afternoon, even with athletes who tend towards ‘morningness’, and who perform a vigorous 25-min warm-up. Diurnal variation in cycling performance is, therefore, relatively robust to some external and behavioural factors. 相似文献
13.
Effects of active,passive or no warm-up on metabolism and performance during high-intensity exercise
The aim of this study was to determine the influence of type of warm-up on metabolism and performance during high-intensity exercise. Eight males performed 30 s of intense exercise at 120% of their maximal power output followed, 1 min later, by a performance cycle to exhaustion, again at 120% of maximal power output. Exercise was preceded by active, passive or no warm-up (control). Muscle temperature, immediately before exercise, was significantly elevated after active and passive warm-ups compared to the control condition (36.9 - 0.18°C, 36.8 - 0.18°C and 33.6 - 0.25°C respectively; mean - sx ) ( P ? 0.05). Total oxygen consumption during the 30 s exercise bout was significantly greater in the active and passive warm-up trials than in the control trial (1017 - 22, 943 - 53 and 838 - 45 ml O 2 respectively). Active warm-up resulted in a blunted blood lactate response during high-intensity exercise compared to the passive and control trials (change = 5.53 - 0.52, 8.09 - 0.57 and 7.90 - 0.38 mmol· l -1 respectively) ( P ? 0.05). There was no difference in exercise time to exhaustion between the active, passive and control trials (43.9 - 4.1, 48.3 - 2.7 and 46.9 - 6.2 s respectively) ( P = 0.69). These results indicate that, although the mechanism by which muscle temperature is elevated influences certain metabolic responses during subsequent high-intensity exercise, cycling performance is not significantly affected. 相似文献
14.
Nine well-trained, unacclimatized female hockey players performed the Loughborough Intermittent Shuttle Test (LIST) interspersed with three field hockey skill tests in hot (30 degrees C, 38% relative humidity) and moderate (19 degrees C, 51% relative humidity) environmental conditions. Field hockey skill performance declined in both the hot and moderate conditions following 30 and 60 min of the LIST compared with pre-LIST values (P < 0.01). This decrement in performance was compounded in the hot environment with a 6% poorer performance in the heat recorded for the second skill test at 30?min (P < 0.05, hot 101.7 +/- 3.6 vs moderate 95.7 +/- 2.9 s; mean +/- s(x)). However, no difference was found in the decision-making element of the skill test. Fifteen-metre sprint times were slower in the hot condition (P < 0.01). In the hot environment, rectal temperature (P < 0.01), perceived exertion (P < 0.05), perceived thirst (P < 0.01), blood glucose concentration (P < 0.05) and serum aldosterone concentration (P < 0.01) were higher. Estimated mean ( +/- s(x)) sweat rate was higher in the hot trial (1.27 +/- 0.10 l.h(-1)) than in the moderate trial (1.05 +/- 0.12 l.h(-1)) (P < 0.05). Body mass was well maintained in both trials. No differences in serum cortisol, blood lactate, plasma volume or plasma ammonia concentrations were found. These results demonstrate that field hockey skill performance is decreased following intermittent high-intensity shuttle running and that this decrease is greater in hot environmental conditions. The exact mechanism for this decrement in performance remains to be elucidated, but is unlikely to be due to low glycogen concentration or dehydration. 相似文献
15.
The purpose of the present study was to re-examine the relationship between deep body temperature and relative exercise intensity, during running rather than cycling (Saltin and Hermansen, 1966). Twenty male competitive and recreational distance runners, aged 22 + 0.9 years (mean +/- sx), were selected to form two groups, one with high maximal oxygen uptake (VO2max) values (72.8 +/- 0.8 ml x kg(-1) x min(-1)) and the other with moderate values (59.4 +/- 0.7 ml x kg(-1) x min(-1)). The participants completed two 60 min constant-paced treadmill runs at a common speed (absolute intensity) of 10.5 km x h(-1) and at a relative exercise intensity at a speed equivalent to 65% of VO2max. During the relative exercise intensity trial, no differences were found in rectal temperature, skin temperature or heart rate between groups. However, when running at the common speed, differences were identified in rectal temperature. At 60 min, rectal temperature was 37.70 +/- 0.19 degrees C and 38.19 +/- 0.11 degrees C for the high and moderate VO2max groups, respectively (P < 0.05). Sweat lost was significantly higher in the moderate VO2max group (moderate: 1.05 +/- 0.06 kg x h(-1); high: 0.82 +/- 0.08 kg x h(-1); P < 0.05). Heart rates were also different between groups over the first 20 min during the common speed trial (P < 0.05). The results of the present study support the findings of Saltin and Hermansen (1966), in that the set-point at which temperature is maintained is related to the relative exercise intensity. 相似文献
16.
In this study, we examined thermoregulatory responses to ingestion of separate aliquots of drinks at different temperatures during low-intensity exercise in conditions of moderate heat stress. Eight men cycled at 50% (s = 3) of their peak oxygen uptake (VO2peak) for 90 min (dry bulb temperature: 25.3 degrees C, s = 0.5; relative humidity: 60%, s = 5). Four 400-ml aliquots of flavoured water at 10 degrees C (cold), 37 degrees C (warm) or 50 degrees C (hot) were ingested after 30, 45, 60, and 75 min of exercise. Immediately after the 90 min of exercise, participants cycled at 95% VO2peak to exhaustion to assess exercise capacity. There were no differences between trials in rectal temperature at the end of the 90 min of exercise (cold: 38.11 degrees C, s = 0.30; warm: 38.10 degrees C, s = 0.33; hot: 38.21 degrees C, s = 0.30; P = 0.765). Mean skin temperature between 30 and 90 min tended to be influenced by drink temperature (cold: 34.49 degrees C, s = 0.64; warm: 34.53 degrees C, s = 0.69; hot: 34.71 degrees C, s = 0.48; P = 0.091). Mean heart rate from 30 to 90 min was higher in the hot trial (129 beats . min(-1), s = 7; P < 0.05) than on the cold (124 beats . min(-1), s = 9) and warm trials (126 beats . min(-1), s = 8). Ratings of thermal sensation were higher on the hot trial than on the cold trial at 35 and 50 min (P < 0.05). Exercise capacity was similar between trials (P = 0.963). The heat load and debt induced by periodic drinking resulted in similar body temperatures during low-intensity exercise in conditions of moderate heat stress due to appropriate thermoregulatory reflexes. 相似文献
17.
Tessa Maroni Brian Dawson Kimberley Barnett Kym Guelfi Carly Brade Louise Naylor 《European Journal of Sport Science》2018,18(4):441-449
This study compared the effects of a hand cooling glove (～16°C water temperature; subatmospheric pressure of ?40 mmHg) and a cooling jacket (CJ) on post-exercise cooling rates (gastrointestinal core temperature, Tc; skin temperature, Tsk) and cognitive performance (the Stroop Colour–Word test). Twelve male athletes performed four trials (within subjects, counterbalanced design) involving cycling at a workload equivalent to 75% ?O2max in heat (35.7?±?0.2°C, 49.2?±?2.6% RH) until a Tc of 39°C or exhaustion occurred. A 30-min cooling period (in 22.3?±?0.3°C, 42.1?±?3.6% RH) followed, where participants adopted either one-hand cooling (1H), two-hand cooling (2H), wore a CJ or no cooling (NC). No significant differences were seen in Tc and Tsk cooling rates between trials; however, moderate effect sizes (d?=?0.50–0.76) suggested Tc cooling rates to be faster for 1H, 2H and CJ compared to NC after 5 min; 1H and CJ compared to NC after 10 min and for CJ to be faster than 2H at 25–30 min. Reaction times on the cognitive test were similar between all trials after the 30 min cooling/no-cooling period (p?>?.05). In conclusion, Tc cooling rates were faster with 1H and CJ during the first 10 min compared to NC, with minimal benefit associated with 2H cooling. Reaction time responses were not impacted by the use of the glove(s) or CJ. 相似文献
18.
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 (nu-VO2max) 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% nu-VO2max. 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% VO2max; 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 x 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 x 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
19.
The effect of an intermittent,high-intensity warm-up on supramaximal kayak ergometer performance 总被引：2，自引：0，他引：2
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 (VO2) 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 VO2max 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% VO2max. The intermittent, high-intensity warm-up was similar, except that the last 5 min was replaced with five 10 s sprints at 200% VO2max, separated by 50 s of recovery at approximately 55% VO2max. Significantly greater (P < 0.05) peak power (intermittent vs continuous: 629 +/- 199 vs 601 +/- 204 W) 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 VO2, total VO2 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
20.
In this study, we examined the effects of upper-body pre-cooling before intermittent sprinting exercise in a moderate environment. Seven male and three female trained cyclists (age 26.8+/-5.5 years, body mass 68.5+/-9.5 kg, height 1.76+/-0.13 m, V O2peak 59.0+/-11.4 mL. kg(-1). min(-1); mean+/-s) performed 30 min of cycling at 50% V O2peak interspersed with a 10-s Wingate cycling sprint test at 5 min intervals. The exercise was performed in a room controlled at 22 degrees C and 40% relative humidity. In the control session, the participants rested for 30 min before exercise. In the pre-cooling session, the participants wore the upper segment of a liquid conditioning garment circulating 5 degrees C coolant until rectal temperature decreased by 0.5 degrees C. Rectal temperature at the start of exercise was significantly lower in the pre-cooling (36.5+/-0.3 degrees C) than in the control condition (37.0+/-0.5 degrees C), but this difference was reduced to a non-significant 0.4 degrees C throughout exercise. Mean skin temperature was significantly lower in the pre-cooling (30.7+/-2.3 degrees C) than in the control condition (32.5+/-1.6 degrees C) throughout exercise. Heart rate during submaximal exercise was similar between the two conditions, although peak heart rate after the Wingate sprints was significantly lower in the pre-cooling condition. With pre-cooling, mean peak power (909+/-161 W) and mean overall power output (797+/-154 W) were similar to those in the control condition (peak 921+/-163 W, mean 806+/-156 W), with no differences in the subjective ratings of perceived exertion. These results suggest that upper-body pre-cooling does not provide any benefit to intermittent sprinting exercise in a moderate environment. 相似文献