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1.
Abstract

High-intensity intermittent exercise substantially increases muscle glucose transport, which is thought to be the rate-limiting step for glycogen synthesis. In the present study, we compared muscle glycogen supercompensation after high-intensity intermittent exercise with that observed after low-intensity continuous exercise in rats. Four- to five-week-old male Sprague-Dawley rats performed either low-intensity swimming (240 min of swimming exercise with a weight equivalent to 1% of their body mass; LOW) or high-intensity swimming (twenty 30-s swimming bouts with 30 s rest between bouts with a weight equivalent to 16% of their body mass; HIGH) to deplete muscle glycogen. After the glycogen-depleting exercise, rats were given a rodent chow diet plus 5% glucose solution for 6 h or 24 h. Immediately after the two types of exercise, glycogen concentration in rat epitrochlearis muscle was similarly depleted. After the 6-h and 24-h recovery periods, muscle glycogen concentrations in both the HIGH and LOW groups were restored well above the normally fed state. Furthermore, muscle glycogen accumulation in the HIGH group for the 6-h and 24-h recovery periods was not significantly different from that observed in the LOW group. The high-intensity intermittent swimming exercise also induced muscle glycogen supercompensation in well-trained rats that had performed 7 days of endurance swimming training (6 h per day). Our results indicate that high-intensity intermittent exercise as well as low-intensity continuous exercise could induce glycogen supercompensation in rat skeletal muscle.  相似文献   

2.
This study was designed to investigate the effect of ingesting a glucose plus fructose solution on the metabolic responses to soccer-specific exercise in the heat and the impact on subsequent exercise capacity. Eleven male soccer players performed a 90 min soccer-specific protocol on three occasions. Either 3 ml · kg(-1) body mass of a solution containing glucose (1 g · min(-1) glucose) (GLU), or glucose (0.66 g · min(-1)) plus fructose (0.33 g · min(-1)) (MIX) or placebo (PLA) was consumed every 15 minutes. Respiratory measures were undertaken at 15-min intervals, blood samples were drawn at rest, half-time and on completion of the protocol, and muscle glycogen concentration was assessed pre- and post-exercise. Following the soccer-specific protocol the Cunningham and Faulkner test was performed. No significant differences in post-exercise muscle glycogen concentration (PLA, 62.99 ± 8.39 mmol · kg wet weight(-1); GLU 68.62 ± 2.70; mmol · kg wet weight(-1) and MIX 76.63 ± 6.92 mmol · kg wet weight(-1)) or exercise capacity (PLA, 73.62 ± 8.61 s; GLU, 77.11 ± 7.17 s; MIX, 83.04 ± 9.65 s) were observed between treatments (P > 0.05). However, total carbohydrate oxidation was significantly increased during MIX compared with PLA (P < 0.05). These results suggest that when ingested in moderate amounts, the type of carbohydrate does not influence metabolism during soccer-specific intermittent exercise or affect performance capacity after exercise in the heat.  相似文献   

3.
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   

4.
In this study, we examined the effects of different work:rest durations during 20 min intermittent treadmill running and subsequent performance. Nine males (mean age 25.8 years, s = 6.8; body mass 73.9 kg, s = 8.8; stature 1.75 m, s = 0.05; VO(2max) 55.5 ml x kg(-1) x min(-1), s = 5.8) undertook repeated sprints at 120% of the speed at which VO(2max) was attained interspersed with passive recovery. The work:rest ratio was constant (1:1.5) with trials involving either short (6:9 s) or long (24:36 s) work:rest exercise protocols (total exercise time 8 min). Each trial was followed by a performance run to volitional exhaustion at the same running speed. Testing order was randomized and counterbalanced. Heart rate, oxygen consumption, respiratory exchange ratio, and blood glucose were similar between trials (P > 0.05). Blood lactate concentration was greater during the long than the short exercise protocol (P < 0.05), whereas blood pH was lower during the long than the short exercise protocol (7.28, s = 0.11 and 7.30, s = 0.03 at 20 min, respectively; P < 0.05). Perceptions of effort were greater throughout exercise for the long than the short exercise protocol (16.6, s = 1.4 and 15.1, s = 1.6 at 20 min, respectively; P < 0.05) and correlated with blood lactate (r = 0.43) and bicarbonate concentrations (r = 0.59; P < 0.05). Although blood lactate concentration at 20 min was related to performance time (r = - 0.56; P < 0.05), no differences were observed between trials for time to exhaustion (short exercise protocol: 95.8 s, s = 30.0; long exercise protocol: 92.0 s, s = 37.1) or physiological responses at exhaustion (P > 0.05). Our results demonstrate that 20 min of intermittent exercise involving a long work:rest duration elicits greater metabolic and perceptual strain than intermittent exercise undertaken with a short work:rest duration but does not affect subsequent run time to exhaustion.  相似文献   

5.
Ghrelin is a hormone that stimulates hunger. Intense exercise has been shown to temporarily suppress hunger after exercise. In the present study, we investigated whether post-exercise hunger suppression is mediated by reduced plasma total ghrelin concentrations. Nine men and nine women participated in the study. Their mean physical characteristics were as follows: age 24.8 (s(x) = 0.9) years, body mass index 22.9 (s(x) = 0.6) kg x m(-2), maximal oxygen uptake (VO(2max)) 57.7 (s(x) = 2.2) ml x kg(-1) x min(-1). The participants completed two 3-h trials (exercise and control) on separate days in a randomized balanced design after overnight fasts. The exercise trial involved a 1-h treadmill run at 73.5% of VO(2max) followed by 2 h of rest. The control trial consisted of 3 h of rest. Blood samples were collected at 0, 0.5, 1, 1.5, 2, and 3 h. Total ghrelin concentrations were determined from plasma. Hunger was assessed following blood sampling using a 15-point scale. The data were analysed using repeated-measures analysis of variance. Hunger scores were lower in the exercise trial than in the control trial (trial, P = 0.009; time, P < 0.001; trial x time, P < 0.001). Plasma total ghrelin concentrations did not differ between trials. These findings indicate that treadmill running suppresses hunger but this effect is not mediated by changes in plasma total ghrelin concentration.  相似文献   

6.
目的：采用大鼠下坡跑运动损伤模型,研究离心力竭运动后不同时刻大鼠骨骼肌肌浆网Ca^2＋-ATP酶活性的变化,探讨离心力竭运动所致骨骼肌超微结构损伤机制,为科学运动训练及运动恢复提供实验和理论依据。方法：雄性SD大鼠60只随机分为6组（每组10只）：安静对照组、运动后即刻组、12h组、24h组、48h组和72h组,以速度16m/min,坡度-16°进行跑台运动,运动100min,休息5min,再运动100min,在不同时刻观察大鼠肱三头肌肌浆网Ca^2＋-ATP酶活性的变化。结果：运动后即刻肌浆网Ca^2＋-ATP酶活性与对照组相比显著下降（P〈0.01）,随后开始恢复,运动后24h接近对照组水平（P〉0.05）,运动后48h已完全恢复到对照组水平。结论：离心力竭运动后即刻大鼠肱三头肌肌浆网Ca^2＋-ATP酶活性显著下降,随后逐渐恢复,运动后24h明显恢复,至48h已完全恢复,肌浆网Ca^2＋-ATP酶活性的变化可以间接评定运动后骨骼肌的损伤。  相似文献   

7.
In this study, we examined the glycaemic and fuel oxidation responses to alterations in the timing of a low glycaemic index carbohydrate and 75% reduced insulin dose, prior to running, in type 1 diabetes individuals. After carbohydrate (75 g isomaltulose) and insulin administration, the seven participants rested for 30 min, 60 min, 90 min or 120 min (conditions 30MIN, 60MIN, 90MIN, and 120MIN, respectively) before completing 45 min of running at 70% peak oxygen uptake. Carbohydrate and lipid oxidation rates were monitored during exercise and blood glucose and insulin were measured before and for 3 h after exercise. Data were analysed using repeated-measures analysis of variance. Pre-exercise blood glucose concentrations were lower for 30MIN compared with 120MIN (P < 0.05), but insulin concentrations were similar. Exercising carbohydrate and lipid oxidation rates were lower and greater, respectively, for 30MIN compared with 120MIN (P < 0.05). The drop in blood glucose during exercise was less for 30MIN (3.7 mmol · l(-1), s(x) = 0.4) compared with 120MIN (6.4 mmol · l(-1), s(x) = 0.3) (P = 0.02). For 60 min post-exercise, blood glucose concentrations were higher for 30MIN compared with 120MIN (P < 0.05). There were no cases of hypoglycaemia in the 30MIN condition, one case in the 60MIN condition, two in the 90MIN condition, and five in the 120MIN condition. In conclusion, a low glycaemic index carbohydrate and reduced insulin dose administered 30 min before running improves pre- and post-exercise blood glucose responses in type 1 diabetes.  相似文献   

8.
补糖对不同时间运动后小鼠酮体代谢的影响   总被引：3，自引：0，他引：3  
将昆明种4~6周龄雄性小白鼠随机分为补糖和补水对照组。每组均设安静组、定量运动组和力竭运动组。补糖采用浓度为5%葡萄糖与7%低聚糖的混合溶液。定量运动组做一次性静水负重游泳运动,持续时间为1h。力竭组与定量组运动形式相同,运动时间至力竭。分别测定血液、肝脏、骨骼肌和脑中的酮体(Ketone Body,KB),肝、骨骼肌糖原以及血糖、脑糖、血清游离脂肪酸(FFA)等指标。结果显示:与补糖组相比,1h游泳运动后补水组血清FFA有升高趋势,但无显著性差异,补水组小鼠血酮体浓度显著升高(P<0.05);力竭运动后补水组骨骼肌、肝脏中酮体含量显著高于补糖组(P<0.05)。提示:小鼠机体糖状况直接影响运动中的酮体代谢,运动性酮体代谢与体内糖储备以及脂肪分解状况有关。  相似文献   

9.
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   

10.
The aim of this study was to assess the sensitivity of the lactate minimum speed test to changes in endurance fitness resulting from a 6 week training intervention. Sixteen participants (mean +/- s: age 23+/-4 years; body mass 69.7+/-9.1 kg) completed 6 weeks of endurance training. Another eight participants (age 23+/-4 years; body mass 72.7+/-12.5 kg) acted as non-training controls. Before and after the training intervention, all participants completed: (1) a standard multi-stage treadmill test for the assessment of VO2max, running speed at the lactate threshold and running speed at a reference blood lactate concentration of 3 mmol x l(-1); and (2) the lactate minimum speed test, which involved two supramaximal exercise bouts and an 8 min walking recovery period to increase blood lactate concentration before the completion of an incremental treadmill test. Additionally, a subgroup of eight participants from the training intervention completed a series of constant-speed runs for determination of running speed at the maximal lactate steady state. The test protocols were identical before and after the 6 week intervention. The control group showed no significant changes in VO2max, running speed at the lactate threshold, running speed at a blood lactate concentration of 3 mmol x l(-1) or the lactate minimum speed. In the training group, there was a significant increase in VO2max (from 47.9+/-8.4 to 52.2+/-2.7 ml x kg(-1) x min(-1)), running speed at the maximal lactate steady state (from 13.3+/-1.7 to 13.9+/-1.6 km x h(-1)), running speed at the lactate threshold (from 11.2+/-1.8 to 11.9+/-1.8 km x h(-1)) and running speed at a blood lactate concentration of 3 mmol x l(-1) (from 12.5+/-2.2 to 13.2+/-2.1 km x h(-1)) (all P < 0.05). Despite these clear improvements in aerobic fitness, there was no significant difference in lactate minimum speed after the training intervention (from 11.0+/-0.7 to 10.9+/-1.7 km x h(-1)). The results demonstrate that the lactate minimum speed, when assessed using the same exercise protocol before and after 6 weeks of aerobic exercise training, is not sensitive to changes in endurance capacity.  相似文献   

11.
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   

12.
Abstract

The purpose of this study was to investigate the effect of melatonin administration on muscle glycogen concentration during recovery after exhaustive swimming exercise in sedentary and trained rats. Male Wistar rats were assigned to one of four groups: sedentary control (C), sedentary melatonin-injected (M), exercise-trained (T), and trained and melatonin-injected (MT) groups. Exercise-trained groups were subjected to six weeks of swimming exercise. All rats completed an exhaustive swimming exercise. Two daily subcutaneous injections of melatonin at a dose of 3 mg·kg?1 were given to the rats in the M and MT groups immediately after the exhaustive exercise. Plasma melatonin, glucose and lactate concentrations, and glycogen concentrations of the soleus and epitrochlearis muscle tissues were measured after exhaustive exercise. Plasma lactate concentration was significantly lower in the T and MT groups than in the C group. Plasma melatonin concentration was higher in the supplemented groups than in the C group. Plasma glucose concentration was significantly higher in the T and MT groups than in the C group. Both epitrochlearis and soleus muscle glycogen concentrations were higher in the trained groups than in the C group. In conclusion, although exercise training results in improvement in muscle glycogen, exogenous melatonin administration after exhaustive exercise did not restore the glycogen concentrations in fast- or slow-twitch muscle tissues.  相似文献   

13.
The aim of the present study was to examine how the recovery of physiological functioning of the leg muscles after high-intensity eccentric exercise such as downhill running could be promoted by aqua exercise for a period until the damaged muscle had recovered almost completely. Ten male long-distance runners were divided equally into an aqua exercise group and a control group. From the first day (Day 0) to the fourth day (Day 3), the participants completed a questionnaire on muscle soreness, and serum creatine kinase activity, muscle power, flexibility, whole-body reaction time and muscle stiffness were measured. After measurements on Day 0, the participants performed downhill running (three 5 min runs with a 5 min rest interval at -10%, 335.7 +/- 6.1 m . min-1). The aqua exercise group performed walking, jogging and jumping in water on three successive days following the downhill running on Day 0 for 30 min each day. Muscle power was reduced on Day 1 in the control group (P < 0.05). Muscle soreness in the calf on Day 3 was greater in the control group than that in the aqua exercise group (P < 0.05). In the aqua exercise group, muscle stiffness in the calf was less than that in the control group over 4 days (time main effect: P < 0.05; group x time interaction: P < 0.05). We conclude that aqua exercise promoted physiological functioning of the muscles in the legs after high-intensity downhill running for a period until the damaged muscles had recovered almost completely.  相似文献   

14.
To examine the influence of pre-warming on the physiological responses to prolonged intermittent exercise in ambient temperatures of 21.5 +/- 0.6 degrees C and relative humidities of 35.7 +/- 5.4% (mean +/- s), six healthy men performed intermittent treadmill running (30-s bouts at 90% of maximal oxygen uptake separated by 30-s static recovery periods) to exhaustion after active pre-warming, passive pre-warming and pre-exercise rest (control). Exercise time to exhaustion was significantly different between all conditions (active, 51.8 +/- 7.2 min; passive, 38.5 +/- 11.1 min; control, 72.0 +/- 17.2 min; P < 0.05). These changes in performance time were closely associated with a significant decline in both the rate of heat storage and heat storage capacity (P < 0.05). Rectal temperature, heart rate and ratings of perceived exertion were significantly higher during exercise in the two pre-warming conditions than in the control condition (P < 0.05). Ratings of perceived exertion were also significantly higher during exercise following passive pre-warming compared with active pre-warming (P < 0.05). During exercise there were no significant differences in serum prolactin, plasma norepinephrine and plasma free fatty acid concentrations between conditions. We conclude that both active and passive pre-warming promote a reduction in prolonged intermittent exercise capacity in environmental temperatures of 21 degrees C compared with pre-exercise rest. These performance decrements were dependent upon the mode of pre-warming and closely reflected alterations in body heat content.  相似文献   

15.
Characteristics of shock attenuation during fatigued running   总被引：1，自引：1，他引：0  
The aim of this study was to examine shock attenuation before and after completing a maximal effort graded exercise test while running on a treadmill. Ten individuals ran before and after a maximal graded exercise test with running speed controlled between conditions. Transfer functions were calculated using surface-mounted accelerometers to represent shock attenuation. An accelerometer was mounted on the distal aspect of the tibia and another on the anterior aspect of the forehead. Ten strides were analysed in each condition for all participants. Paired t-tests were used to compare each dependent variable (shock attenuation, stride length, rate of oxygen consumption) between conditions (running before vs after the exercise test). Oxygen consumption was 16% greater when running after the graded exercise test (47.9 +/- 5.0 ml x kg(-1) x min(-1); mean+/-s) than when running before it (41.1 +/- 2.7 ml x kg(-1) x min(-1)) (P < 0.05). Stride length was similar during running before (2.71 +/- 0.15 m) and after (2.75 +/- 0.17 m) the graded exercise test (P > 0.05). Shock attenuation was, on average, 12% lower during running after (-9.8 +/- 2.6 dB) than before (-11.3 +/- 2.7 dB) the graded exercise test (P < 0.05). We conclude that less shock was attenuated during fatigued than non-fatigued running and that only subtle changes in stride length were made while fatigued.  相似文献   

16.
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   

17.
The "feel better" effect of exercise has been well established, but the optimal intensity needed to elicit a positive affective response is controversial. In addition, the mechanisms underlying such a response are unclear To clarify these issues, female undergraduate students were monitored for electroencephalographic (EEG) and self-reported affective responses during the recovery period following rest, low, moderate, and high intensities of treadmill running, each lasting 30 min. Frontal EEG asymmetry and self-reported vigor scores following exercise at all three intensities were significantly elevated compared to those observed following rest. The results suggest that steady-state aerobic exercise bouts executed at varying intensities induce a similar affective response during the recovery period when assessed at both the behavioral and psychophysiological levels.  相似文献   

18.
The “feel better” effect of exercise has been well established, but the optimal intensity needed to elicit a positive affective response is controversial. In addition, the mechanisms underlying such a response are unclear. To clarify these issues, female undergraduate students were monitored for electroencephalographic (EEG) and self-reported affective responses during the recovery period following rest, low, moderate, and high intensities of treadmill running, each lasting 30 min. Frontal EEG asymmetry and self-reported vigor scores following exercise at all three intensities were significantly elevated compared to those observed following rest. The results suggest that steady-state aerobic exercise bouts executed at varying intensities induce a similar affective response during the recovery period when assessed at both the behavioral and psychophysiological levels.  相似文献   

19.
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% V O 2m ax ; estimated from measurement of heart rate) remained constant (83.4 ± 0.9% HR m ax ; mean s x ) after the second change of end. The peak value for estimated play intensity (1.25 ± 0.11 steps . 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 . l -1 at rest to a peak 5.86 ± 1.33 mmol . l -1 after the sixth change of end (P < 0.001). A linear regression model, which included significant terms for %HR m ax (P < 0.001) and subject (P < 0.001), as well as a %HR max subject interaction (P < 0.05), accounted for 82% of the variation in plasma lactate concentration. During intermittent laboratory treadmill running, % V O 2peak estimated from heart rate was 17% higher than the value derived from the measured V O 2 (79.7 ± 2.2% and 69.0 ± 2.5% V O 2peak respectively; P < 0.001). The % V O 2peak 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 V O 2 , will overestimate the aerobic response. (P < 0.001), estimated play intensity  相似文献   

20.
A key goal of pre-exercise nutritional strategies is to maximize carbohydrate stores, thereby minimizing the ergolytic effects of carbohydrate depletion. Increased dietary carbohydrate intake in the days before competition increases muscle glycogen levels and enhances exercise performance in endurance events lasting 90 min or more. Ingestion of carbohydrate 3-4 h before exercise increases liver and muscle glycogen and enhances subsequent endurance exercise performance. The effects of carbohydrate ingestion on blood glucose and free fatty acid concentrations and carbohydrate oxidation during exercise persist for at least 6 h. Although an increase in plasma insulin following carbohydrate ingestion in the hour before exercise inhibits lipolysis and liver glucose output, and can lead to transient hypoglycaemia during subsequent exercise in susceptible individuals, there is no convincing evidence that this is always associated with impaired exercise performance. However, individual experience should inform individual practice. Interventions to increase fat availability before exercise have been shown to reduce carbohydrate utilization during exercise, but do not appear to have ergogenic benefits.  相似文献   

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