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1.
The aim of this study was to assess the responses of blood lactate and pyruvate during the lactate minimum speed test. Ten participants (5 males, 5 females; mean +/- s: age 27.1+/-6.7 years, VO2max 52.0+/-7.9 ml x kg(-1) x min(-1)) completed: (1) the lactate minimum speed test, which involved supramaximal sprint exercise to invoke a metabolic acidosis before the completion of an incremental treadmill test (this results in a 'U-shaped' blood lactate profile with the lactate minimum speed being defined as the minimum point on the curve); (2) a standard incremental exercise test without prior sprint exercise for determination of the lactate threshold; and (3) the sprint exercise followed by a passive recovery. The lactate minimum speed (12.0+/-1.4 km x h(-1)) was significantly slower than running speed at the lactate threshold (12.4+/-1.7 km x h(-1)) (P < 0.05), but there were no significant differences in VO2, heart rate or blood lactate concentration between the lactate minimum speed and running speed at the lactate threshold. During the standard incremental test, blood lactate and the lactate-to-pyruvate ratio increased above baseline values at the same time, with pyruvate increasing above baseline at a higher running speed. The rate of lactate, but not pyruvate, disappearance was increased during exercising recovery (early stages of the lactate minimum speed incremental test) compared with passive recovery. This caused the lactate-to-pyruvate ratio to fall during the early stages of the lactate minimum speed test, to reach a minimum point at a running speed that coincided with the lactate minimum speed and that was similar to the point at which the lactate-to-pyruvate ratio increased above baseline in the standard incremental test. Although these results suggest that the mechanism for blood lactate accumulation at the lactate minimum speed and the lactate threshold may be the same, disruption to normal submaximal exercise metabolism as a result of the preceding sprint exercise, including a three- to five-fold elevation of plasma pyruvate concentration, makes it difficult to interpret the blood lactate response to the lactate minimum speed test. Caution should be exercised in the use of this test for the assessment of endurance capacity.  相似文献   

2.
Above the lactate/ventilatory threshold, prolonged steady-state exercise produces a secondary rise in oxygen uptake, the slow oxygen component. The slow oxygen component 'represents an additional energetic requirement' above steady state; however, a lack of consensus on how to measure anaerobic energy expenditure makes it difficult to ascertain how or if anaerobic metabolism also contributes to energy expenditure. The aim of this study was to establish if the slow oxygen component is the sole source of 'additional energetic requirements' during steady-state exercise above the lactate/ventilatory threshold. Ten participants completed an 8 min continuous treadmill run and four 2 min intermittent runs at a speed of 2.67 m x s(-1) and a grade located halfway between the ventilatory threshold and maximum oxygen uptake. Each participant performed five submaximal runs below the ventilatory threshold to estimate energy expenditure at this exercise intensity. Both the oxygen deficit and the slow oxygen component were derived from this estimated energy expenditure. Oxygen equivalent units (ml O2) were used for comparison. The slow oxygen component for the 8 min continuous run began 2-4 min into exercise (73 ml O2), rose quickly at 4 6 min (178 ml O2) and declined at 6-8 min (96 ml O2). For the intermittent 2 min runs, a decrease in the oxygen deficit was seen between the first and second trial (-273 ml O2), indicating a larger aerobic energy expenditure contribution. The oxygen deficit began to increase when the third and fourth trials (+62 ml O2) were compared, suggesting a larger contribution to anaerobic energy expenditure. At the end of exercise, the intermittent oxygen deficit and continuous slow oxygen component revealed inverse associations; that is, in participants with large slow oxygen component contributions, the oxygen deficit was minimal; participants who had an increased oxygen deficit had smaller slow oxygen component contributions. The results suggest larger aerobic contributions to 'additional energetic requirements' when the slow oxygen component itself is large; however, smaller slow oxygen components do not necessarily indicate a lower energy expenditure. Individuals with smaller slow oxygen components during continuous exercise have larger oxygen deficits during intermittent exercise; thus an anaerobic contribution to the 'additional energetic requirement' may exist.  相似文献   

3.
This study was designed to examine the magnitude and duration of excess postexercise oxygen consumption (EPOC) following upper body exercise, using lower body exercise for comparison. On separate days and in a counterbalanced order, eight subjects (four male and four female) performed a 20-min exercise at 60% of mode-specific peak oxygen uptake (VO2) using an arm crank and cycle ergometer. Prior to each exercise, baseline VO2 and heart rate (HR) were measured during the final 15 min of a 45-min seated rest. VO2 and HR were measured continuously during the postexercise period until baseline VO2 was reestablished. No significant difference between the two experimental conditions was found for magnitude of EPOC (t [7] = 0.69, p greater than .05). Mean (+/- SD) values were 9.2 +/- 3.3 and 10.4 +/- 5.8 kcal for the arm crank and cycle ergometer exercises, respectively. Duration of EPOC was relatively short and not significantly different (t [7] = 0.24, p greater than .05) between the upper body (22.9 +/- 13.7 min) and lower body (24.2 +/- 19.4 min) exercises. Within the framework of the chosen exercise conditions, these results suggest EPOC may be related primarily to the relative metabolic rate of the active musculature, as opposed to the absolute exercise VO2 or quantity of active muscle mass associated with these two types of exercise.  相似文献   

4.
Recovery from a bout of exercise is associated with an elevation in metabolism referred to as the excess post-exercise oxygen consumption (EPOC). A number of investigators in the first half of the last century reported prolonged EPOC durations and that the EPOC was a major component of the thermic effect of activity. It was therefore thought that the EPOC was a major contributor to total daily energy expenditure and hence the maintenance of body mass. Investigations conducted over the last two or three decades have improved the experimental protocols used in the pioneering studies and therefore have more accurately characterized the EPOC. Evidence has accumulated to suggest an exponential relationship between exercise intensity and the magnitude of the EPOC for specific exercise durations. Furthermore, work at exercise intensities >or=50-60% VO2max stimulate a linear increase in EPOC as exercise duration increases. The existence of these relationships with resistance exercise at this stage remains unclear because of the limited number of studies and problems with quantification of work intensity for this type of exercise. Although the more recent studies do not support the extended EPOC durations reported by some of the pioneering investigators, it is now apparent that a prolonged EPOC (3-24 h) may result from an appropriate exercise stimulus (submaximal: >or=50 min at >or=70% VO2max; supramaximal: >or=6 min at >or=105% VO2max). However, even those studies incorporating exercise stimuli resulting in prolonged EPOC durations have identified that the EPOC comprises only 6-15% of the net total oxygen cost of the exercise. But this figure may need to be increased when studies utilizing intermittent work bouts are designed to allow the determination of rest interval EPOCs, which should logically contribute to the EPOC determined following the cessation of the last work bout. Notwithstanding the aforementioned, the earlier research optimism regarding an important role for the EPOC in weight loss is generally unfounded. This is further reinforced by acknowledging that the exercise stimuli required to promote a prolonged EPOC are unlikely to be tolerated by non-athletic individuals. The role of exercise in the maintenance of body mass is therefore predominantly mediated via the cumulative effect of the energy expenditure during the actual exercise.  相似文献   

5.
In this study, we examined the effects of three recovery intensities on time spent at a high percentage of maximal oxygen uptake (t90[Vdot]O(2max)) during a short intermittent session. Eight endurance-trained male adolescents (16 +/- 1 years) performed four field tests until exhaustion: a graded test to determine maximal oxygen uptake ([Vdot]O(2max); 57.4 +/- 6.1 ml x min(-1) . kg(-1)) and maximal aerobic velocity (17.9 +/- 0.4 km x h(-1)), and three intermittent exercises consisting of repeat 30-s runs at 105% of maximal aerobic velocity alternating with 30 s active recovery at 50% (IE(50)), 67% (IE(67)), and 84% (IE(84)) of maximal aerobic velocity. In absolute values, mean t90[Vdot]O(2max) was not significantly different between IE(50) and IE(67), but both values were significantly longer compared with IE(84). When expressed in relative values (as a percentage of time to exhaustion), mean t90[Vdot]O(2max) was significantly higher during IE(67) than during IE(50). Our results show that both 50% and 67% of maximal aerobic velocity of active recovery induced extensive solicitation of the cardiorespiratory system. Our results suggest that the choice of recovery intensity depends on the exercise objective.  相似文献   

6.
Maximal oxygen uptake VO(2max)) is considered the optimal method to assess aerobic fitness. The measurement of VO(2max), however, requires special equipment and training. Maximal exercise testing with determination of maximal power output offers a more simple approach. This study explores the relationship between [Vdot]O(2max) and maximal power output in 247 children (139 boys and 108 girls) aged 7.9-11.1 years. Maximal oxygen uptake was measured by indirect calorimetry during a maximal ergometer exercise test with an initial workload of 30 W and 15 W x min(-1) increments. Maximal power output was also measured. A sample (n = 124) was used to calculate reference equations, which were then validated using another sample (n = 123). The linear reference equation for both sexes combined was: VO(2max) (ml x min(-1)) = 96 + 10.6 x maximal power + 3.5 . body mass. Using this reference equation, estimated VO(2max) per unit of body mass (ml x min(-1) x kg(-1)) calculated from maximal power correlated closely with the direct measurement of VO(2max) (r = 0.91, P <0.001). Bland-Altman analysis gave a mean limits of agreement of 0.2+/-2.9 (ml x min(-1) x kg(-1)) (1 s). Our results suggest that maximal power output serves as a good surrogate measurement for VO(2max) in population studies of children aged 8-11 years.  相似文献   

7.
The aims of the study were to modify the training impulse (TRIMP) method of quantifying training load for use with intermittent team sports, and to examine the relationship between this modified TRIMP (TRIMP(MOD)) and changes in the physiological profile of team sport players during a competitive season. Eight male field hockey players, participating in the English Premier Division, took part in the study (mean+/-s: age 26+/-4 years, body mass 80.8+/-5.2 kg, stature 1.82+/-0.04 m). Participants performed three treadmill exercise tests at the start of the competitive season and mid-season: a submaximal test to establish the treadmill speed at a blood lactate concentration of 4 mmol . l(-1); a maximal incremental test to determine maximal oxygen uptake ([V]O(2max)) and peak running speed; and an all-out constant-load test to determine time to exhaustion. Heart rate was recorded during all training sessions and match-play, from which TRIMP(MOD) was calculated. Mean weekly TRIMP(MOD) was correlated with the change in [V]O(2max) and treadmill speed at a blood lactate concentration of 4 mmol x l(-1) from the start of to mid-season (P<0.05). The results suggest that TRIMP(MOD) is a means of quantifying training load in team sports and can be used to prescribe training for the maintenance or improvement of aerobic fitness during the competitive season.  相似文献   

8.
The aim of this study was to examine heart rate, blood lactate concentration and estimated energy expenditure during a competitive rugby league match. Seventeen well-trained rugby league players (age, 23.9 +/- 4.1 years; VO2max, 57.9 +/- 3.6 ml x kg(-1) x min(-1); height, 1.82 +/- 0.06 m; body mass, 90.2 +/- 9.6 kg; mean +/- s) participated in the study. Heart rate was recorded continuously throughout the match using Polar Vantage NV recordable heart rate monitors. Blood lactate samples (n = 102) were taken before the match, after the warm-up, at random stoppages in play, at half time and immediately after the match. Estimated energy expenditure during the match was calculated from the heart rate-VO2 relationship determined in laboratory tests. The mean team heart rate (n = 15) was not significantly different between halves (167 +/- 9 vs 165 +/- 11 beats x min(-1)). Mean match intensity was 81.1 +/- 5.8% VO2max. Mean match blood lactate concentration was 7.2 +/- 2.5 mmol x l(-1), with concentrations for the first half (8.4 +/- 1.8 mmol x l(-1)) being significantly higher than those for the second half (5.9 +/- 2.5 mmol x l(-1)) (P<0.05). Energy expenditure was approximately 7.9 MJ. These results demonstrate that semi-professional rugby league is a highly aerobic game with a considerable anaerobic component requiring high lactate tolerance. Training programmes should reflect these demands placed on players during competitive match-play.  相似文献   

9.
The aim of this study was to examine the acute effects of prolonged static stretching (SS) on running economy. Ten male runners (VO2(peak) 60.1 +/- 7.3 ml x kg(-1) x min(-1)) performed 10 min of treadmill running at 70% VO2(peak) before and after SS and no stretching interventions. For the stretching intervention, each leg was stretched unilaterally for 40 s with each of eight different exercises and this was repeated three times. Respiratory gas exchange was measured throughout the running exercise with an automated gas analysis system. On a separate day, participants were tested for sit and reach range of motion, isometric strength and countermovement jump height before and after SS. The oxygen uptake, minute ventilation, energy expenditure, respiratory exchange ratio and heart rate responses to running were unaffected by the stretching intervention. This was despite a significant effect of SS on neuromuscular function (sit and reach range of motion, +2.7 +/- 0.6 cm; isometric strength, -5.6% +/- 3.4%; countermovement jump height -5.5% +/- 3.4%; all P < 0.05). The results suggest that prolonged SS does not influence running economy despite changes in neuromuscular function.  相似文献   

10.
The aims of this study were to quantify the effects of factors such as mode of exercise, body composition and training on the relationship between heart rate and physical activity energy expenditure (measured in kJ x min(-1)) and to develop prediction equations for energy expenditure from heart rate. Regularly exercising individuals (n = 115; age 18-45 years, body mass 47-120 kg) underwent a test for maximal oxygen uptake (VO2max test), using incremental protocols on either a cycle ergometer or treadmill; VO2max ranged from 27 to 81 ml x kg(-1) x min(-1). The participants then completed three steady-state exercise stages on either the treadmill (10 min) or the cycle ergometer (15 min) at 35%, 62% and 80% of VO2max, corresponding to 57%, 77% and 90% of maximal heart rate. Heart rate and respiratory exchange ratio data were collected during each stage. A mixed-model analysis identified gender, heart rate, weight, V2max and age as factors that best predicted the relationship between heart rate and energy expenditure. The model (with the highest likelihood ratio) was used to estimate energy expenditure. The correlation coefficient (r) between the measured and estimated energy expenditure was 0.913. The model therefore accounted for 83.3% (R2) of the variance in energy expenditure in this sample. Because a measure of fitness, such as VO2max, is not always available, a model without VO2max included was also fitted. The correlation coefficient between the measured energy expenditure and estimates from the mixed model without VO2max was 0.857. It follows that the model without a fitness measure accounted for 73.4% of the variance in energy expenditure in this sample. Based on these results, we conclude that it is possible to estimate physical activity energy expenditure from heart rate in a group of individuals with a great deal of accuracy, after adjusting for age, gender, body mass and fitness.  相似文献   

11.
Reduced hepatic lactate elimination initiates blood lactate accumulation during incremental exercise. In this study, we wished to determine whether renal lactate elimination contributes to the initiation of blood lactate accumulation. The renal arterial-to-venous (a-v) lactate difference was determined in nine men during sodium lactate infusion to enhance the evaluation (0.5 mol x L(-1) at 16 ± 1 mL x min(-1); mean ± s) both at rest and during cycling exercise (heart rate 139 ± 5 beats x min(-1)). The renal release of erythropoietin was used to detect kidney tissue ischaemia. At rest, the a-v O(2) (CaO(2)-CvO(2)) and lactate concentration differences were 0.8 ± 0.2 and 0.02 ± 0.02 mmol x L(-1), respectively. During exercise, arterial lactate and CaO(2)-CvO(2) increased to 7.1 ± 1.1 and 2.6 ± 0.8 mmol x L(-1), respectively (P < 0.05), indicating a -70% reduction of renal blood flow with no significant change in the renal venous erythropoietin concentration (0.8 ± 1.4 U x L(-1)). The a-v lactate concentration difference increased to 0.5 ± 0.8 mmol x L(-1), indicating similar lactate elimination as at rest. In conclusion, a -70% reduction in renal blood flow does not provoke critical renal ischaemia, and renal lactate elimination is maintained. Thus, kidney lactate elimination is unlikely to contribute to the initial blood lactate accumulation during progressive exercise.  相似文献   

12.
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   

13.
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   

14.
The aim of this study was to determine the reproducibility of the maximal accumulated oxygen deficit and the associated exercise time to exhaustion during short-distance running. Fifteen well-trained males (mean +/- s: VO2max = 58.0+/-4.6 ml x kg(-1) x min(-1)) performed the maximum accumulated oxygen deficit test at an exercise intensity equivalent to 125% VO2max. The test was repeated at the same time of day on three occasions within 3 weeks. There was no significant systematic bias between trials for either maximum accumulated oxygen deficit (man +/- s: trial 1 = 69.0+/-13.1; trial 2 = 71.4+/-12.5; trial 3 = 70.4+/-15.0 ml O2 Eq x kg(-1); ANOVA, F = 0.70, PP= 0.51) or exercise time to exhaustion (trial 1 = 194 + 31.1; trial 2 = 198 + 33.2; trial 3 = 201 + 36.8 s; F= 1.49, P = 0.24). In addition, other traditional measures of reliability were also favourable. These included intraclass correlation coefficients of 0.91 and 0.87, and sample coefficients of variation of 6.8% and 5.0%, for maximum accumulated oxygen deficit and exercise time to exhaustion respectively. However, the '95% limits of agreement' were 0+/-15.1 ml O2 Eq (1.01 multiply/divide 1.26 as a ratio) and 0+/-33.5 s (1.0 multiply/divide 1.18 as a ratio) for maximum accumulated oxygen deficit and exercise time to exhaustion respectively. We estimate that the sample sizes required to detect a 10% change in exercise time to exhaustion and maximum accumulated oxygen deficit after a repeated measures experiment are 10 and 20 respectively. Unlike the results of previous maximum accumulated oxygen deficit studies, we conclude that it is not a reliable measure.  相似文献   

15.
The purpose of this study was to provide a more detailed analysis of performance in cross-country skiing by combining findings from a differential global positioning system (dGPS), metabolic gas measurements, speed in different sections of a ski-course and treadmill threshold data. Ten male skiers participated in a freestyle skiing field test (5.6 km), which was performed with dGPS and metabolic gas measurements. A treadmill running threshold test was also performed and the following parameters were derived: anaerobic threshold, threshold of decompensated metabolic acidosis, respiratory exchange ratio = 1, onset of blood lactate accumulation and peak oxygen uptake (VO2peak). The combined dGPS and metabolic gas measurements made detailed analysis of performance possible. The strongest correlations between the treadmill data and final skiing field test time were for VO2peak (l x min(-1)), respiratory exchange ratio = 1 (l x min(-1)) and onset of blood lactate accumulation (l x min(-1)) (r = -0.644 to - 0.750). However, all treadmill test data displayed stronger associations with speed in different stretches of the course than with final time, which stresses the value of a detailed analysis of performance in cross-country skiing. Mean oxygen uptake (VO2) in a particular stretch in relation to speed in the same stretch displayed its strongest correlation coefficients in most stretches when VO2 was presented in units litres per minute, rather than when VO2 was normalized to body mass (ml x kg(-1) x min(-1) and ml x min(-1) x kg(-2/3)). This suggests that heavy cross-country skiers have an advantage over their lighter counterparts. In one steep uphill stretch, however, VO2 (ml x min(-1) x kg(-2/3)) displayed the strongest association with speed, suggesting that in steep uphill sections light skiers could have an advantage over heavier skiers.  相似文献   

16.
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   

17.
Abstract

Exercise-induced muscle damage (EIMD), described as the acute weakness of the musculature after unaccustomed eccentric exercise, increases oxidative metabolism at rest and during endurance exercise. However, it is not known whether oxygen uptake during recovery from endurance exercise is increased when experiencing symptoms of EIMD. Therefore, the purpose of this study was to investigate the effects of EIMD on physiological and metabolic responses before, during and after sub-maximal running. After a 12 h fast, eight healthy male participants completed baseline measurements comprising resting metabolic rate (RMR), indirect markers of EIMD, 10 min of sub-maximal running and 30 min of recovery to ascertain excess post-exercise oxygen consumption (EPOC). Measurements were then repeated at 24 and 48 h after 100 Smith-machine squats. Data analysis revealed significant (P<0.05) increases in muscle soreness and creatine kinase (CK) and decreases in peak knee extensor torque at 24 and 48 h after squatting exercise. Moreover, RMR, physiological, metabolic and perceptual responses during sub-maximal running and EPOC were increased in the two days after squatting exercise (P<0.05). It is suggested that the elevated RMR was a consequence of a raised energy requirement for the degradation and resynthesis of damaged muscle fibres. The increased oxygen demand during sub-maximal running after muscle damage was responsible for the increase in EPOC. Individuals engaging in unaccustomed resistance exercise that results in muscle damage should be mindful of the increases in resting energy expenditure and increased metabolic demand to exercise in the days that follow.  相似文献   

18.
Abstract

Recovery from a bout of exercise is associated with an elevation in metabolism referred to as the excess post-exercise oxygen consumption (EPOC). A number of investigators in the first half of the last century reported prolonged EPOC durations and that the EPOC was a major component of the thermic effect of activity. It was therefore thought that the EPOC was a major contributor to total daily energy expenditure and hence the maintenance of body mass. Investigations conducted over the last two or three decades have improved the experimental protocols used in the pioneering studies and therefore have more accurately characterized the EPOC. Evidence has accumulated to suggest an exponential relationship between exercise intensity and the magnitude of the EPOC for specific exercise durations. Furthermore, work at exercise intensities ≥50 – 60% [Vdot]O2max stimulate a linear increase in EPOC as exercise duration increases. The existence of these relationships with resistance exercise at this stage remains unclear because of the limited number of studies and problems with quantification of work intensity for this type of exercise. Although the more recent studies do not support the extended EPOC durations reported by some of the pioneering investigators, it is now apparent that a prolonged EPOC (3 – 24 h) may result from an appropriate exercise stimulus (submaximal: ≥50 min at ≥70% [Vdot]O2max; supramaximal: ≥6 min at ≥105% [Vdot]O2max). However, even those studies incorporating exercise stimuli resulting in prolonged EPOC durations have identified that the EPOC comprises only 6 – 15% of the net total oxygen cost of the exercise. But this figure may need to be increased when studies utilizing intermittent work bouts are designed to allow the determination of rest interval EPOCs, which should logically contribute to the EPOC determined following the cessation of the last work bout. Notwithstanding the aforementioned, the earlier research optimism regarding an important role for the EPOC in weight loss is generally unfounded. This is further reinforced by acknowledging that the exercise stimuli required to promote a prolonged EPOC are unlikely to be tolerated by non-athletic individuals. The role of exercise in the maintenance of body mass is therefore predominantly mediated via the cumulative effect of the energy expenditure during the actual exercise.  相似文献   

19.
This study investigated the effect of a single session of resistance exercise on postprandial lipaemia. Eleven healthy normolipidaemic men with a mean age of 23 (standard error = 1.4) years performed two trials at least 1 week apart in a counterbalanced randomized design. In each trial, participants consumed a test meal (1.2 g fat, 1.1 g carbohydrate, 0.2 g protein and 68 kJ x kg(-1) body mass) between 08.00 and 09.00 h following a 12 h fast. The afternoon before one trial, the participants performed an 88 min bout of resistance exercise. Before the other trial, the participants were inactive (control trial). Resistance exercise was performed using free weights and included four sets of 10 repetitions of each of 11 exercises. Sets were performed at 80% of 10-repetition maximum with a 2 min work and rest interval. Venous blood samples were obtained in the fasted state and at intervals for 6 h postprandially. Fasting plasma triacylglycerol (TAG) concentration did not differ significantly between control (1.03 +/- 0.13 mmol x l(-1)) and exercise (0.94 +/- 0.09 mmol x l(-1)) trials (mean +/- standard error). Similarly, the 6 h total area under the plasma TAG concentration versus time curve did not differ significantly between the control (9.84 +/- 1.40 mmol l(-1) x 6 h(-1)) and exercise (9.38 +/- 1.12 mmol x l(-1) x 6 h(-1)) trials. These findings suggest that a single session of resistance exercise does not reduce postprandial lipaemia.  相似文献   

20.
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   

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