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1.
We evaluated the effects of specific inspiratory muscle training on simulated time-trial performance in trained cyclists. Using a double-blind, placebo-controlled design, 16 male cyclists (VO 2max = 64 - 2 ml·kg -1 ·min -1 ; mean - sx ¥ ) were assigned at random to either an experimental (pressure-threshold inspiratory muscle training) or sham-training control (placebo) group. Pulmonary function, maximum dynamic inspiratory muscle function and the physiological and perceptual responses to maximal incremental cycling were assessed. Simulated time-trial performance (20 and 40 km) was quantified as the time to complete pre-set amounts of work. Pulmonary function was unchanged after the intervention, but dynamic inspiratory muscle function improved in the inspiratory muscle training group ( P h 0.05). After the intervention, the inspiratory muscle training group experienced a reduction in the perception of respiratory and peripheral effort (Borg CR10: 16 - 4% and 18 - 4% respectively; compared with placebo, P h 0.01) and completed the simulated 20 and 40 km time-trials faster than the placebo group [66 - 30 and 115 - 38 s (3.8 - 1.7% and 4.6 - 1.9%) faster respectively; P = 0.025 and 0.009]. These results support evidence that specific inspiratory muscle training attenuates the perceptual response to maximal incremental exercise. Furthermore, they provide evidence of performance enhancements in competitive cyclists after inspiratory muscle training.  相似文献   

2.
We evaluated the effects of specific inspiratory muscle training on simulated time-trial performance in trained cyclists. Using a double-blind, placebo-controlled design, 16 male cyclists (VO2max = 64 +/- 2 ml x kg(-1) x min(-1); mean +/- s(x)) were assigned at random to either an experimental (pressure-threshold inspiratory muscle training) or sham-training control (placebo) group. Pulmonary function, maximum dynamic inspiratory muscle function and the physiological and perceptual responses to maximal incremental cycling were assessed. Simulated time-trial performance (20 and 40 km) was quantified as the time to complete pre-set amounts of work. Pulmonary function was unchanged after the intervention, but dynamic inspiratory muscle function improved in the inspiratory muscle training group (P < or = 0.05). After the intervention, the inspiratory muscle training group experienced a reduction in the perception of respiratory and peripheral effort (Borg CR10: 16 +/- 4% and 18 +/- 4% respectively; compared with placebo, P < or = 0.01) and completed the simulated 20 and 40 km time-trials faster than the placebo group [66 +/- 30 and 115 +/- 38 s (3.8 +/- 1.7% and 4.6 +/- 1.9%) faster respectively; P = 0.025 and 0.009]. These results support evidence that specific inspiratory muscle training attenuates the perceptual response to maximal incremental exercise. Furthermore, they provide evidence of performance enhancements in competitive cyclists after inspiratory muscle training.  相似文献   

3.
Respiratory muscle fatigue has been reported following short bouts of high-intensity exercise, and prolonged, moderate-intensity exercise, as evidenced by decrements in inspiratory and expiratory mouth pressures. However, links to functionally relevant outcomes such as breathing effort have been lacking. The present study examined dyspnoea and leg fatigue during a treadmill marathon in nine experienced runners. Maximal inspiratory and expiratory pressure, peak inspiratory and expiratory flow, forced vital capacity, and forced expiratory volume in one second were assessed before, immediately after, and four and 24 hours after a marathon. During the run, leg effort was rated higher than respiratory effort from 18 through 42 km (P < 0.05). Immediately after the marathon, there were significant decreases in maximal inspiratory pressure and peak inspiratory flow (from 118 +/- 20 cm H(2)O and 6.3 +/- 1.4 litres x s(-1) to 100 +/- 22 cm H(2)O and 4.9 +/- 1.5 litres x s(-1) respectively; P < 0.01), while expiratory function remained unchanged. Leg maximum voluntary contraction force was significantly lower post-marathon. Breathing effort correlated significantly with leg fatigue (r = 0.69), but not inspiratory muscle fatigue. Our results confirm that prolonged moderate-intensity exercise induces inspiratory muscle fatigue. Furthermore, they suggest that the relative intensity of inspiratory muscle work during exercise makes some contribution to leg fatigue.  相似文献   

4.
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   

5.
The effects of strength training of the quadriceps on peak power output during isokinetic cycling has been investigated in group of 17 young healthy volunteers. Subjects trained by lifting near-maximal loads on a leg extension machine for 12 weeks. Measurements of maximal voluntary isometric force were made at 2-3 week intervals and a continual record was kept of the weights lifted in training. Peak power output was measured at 110 rev min-1 and at either 70 or 80 rev min-1 before and after the 12 week training period. Measurements of maximum oxygen uptake (VO2max) were made on 12 subjects before and after training. The greatest change was in the weights lifted in training which increased by 160-200%. This was accompanied by a much smaller increase in maximum isometric force (3-20%). There was no significant change in peak power output at either speed. The VO2max remained unchanged with training. The role of task specificity in training is discussed in relation to training regimes for power athletes and for rehabilitation of patients with muscle weakness.  相似文献   

6.
Traditionally, it has been assumed that during middle-distance running oxygen uptake (VO2) reaches its maximal value (VO2max) providing the event is of a sufficient duration; however, this assumption is largely based on observations in individuals with a relatively low VO2max. The aim of this study was to determine whether VO2max is related to the VO2 attained (i.e. VO2peak) during middle-distance running on a treadmill. Fifteen well-trained male runners (age 23.3 +/- 3.8 years, height 1.80 +/- 0.10 m, body mass 76.9 +/- 10.6 kg) volunteered to participate in the study. The participants undertook two 800-m trials to examine the reproducibility of the VO2 response. These two trials, together with a progressive test to determine VO2max, were completed in a randomized order. Oxygen uptake was determined throughout each test using 15-s Douglas bag collections. Following the application of a 30-s rolling average, the highest VO2 during the progressive test (i.e. VO2max) was compared with the highest VO2 during the 800-m trials (i.e. VO2peak) to examine the relationship between VO2max and the VO2 attained in the 800-m trials. For the 15 runners, VO2max was 58.9 +/- 7.1 ml x kg(-1) x min(-1). Two groups were formed using a median split based on VO2max. For the high and low VO2max groups, VO2max was 65.7 +/- 3.0 and 52.4 +/- 1.8 ml x kg(-1) x min(-1) respectively. The limits of agreement (95%) for test-retest reproducibility for the VO2 attained during the 800-m trials were +/- 3.5 ml x kg(-1) x min(-1) for a VO2peak of 50.6 ml x kg(-1) x min(-1) (the mean VO2peak for the low VO2max group) and +/- 2.3 ml x kg(-1) x min(-1) for a VO2peak of 59.0 ml x kg(-1) x min(-1) (the mean VO2peak for the high VO2max group), with a bias in VO2peak between the 800-m runs (i.e. the mean difference) of 1.2 ml x kg(-1) x min(-1). The VO2peak for the 800-m runs was 54.8 +/- 4.9 ml x kg(-1) x min(-1) for all 15 runners. For the high and low VO2max groups, VO2peak was 59.0 +/- 3.3 ml x kg(-1) x min(-1) (i.e. 90% VO2max) and 50.6 +/- 2.0 ml x kg(-1) x min(-1) (i.e. 97% VO2max) respectively. The negative relationship (-0.77) between VO2max and % VO2max attained for all 15 runners was significant (P = 0.001). These results demonstrate that (i) reproducibility is good and (ii) that VO2max is related to the %VO2max achieved, with participants with a higher VO2max achieving a lower %VO2max in an 800-m trial on a treadmill.  相似文献   

7.
ABSTRACT

Exercise-induced arterial hypoxemia (EIAH) has been consistently reported in elite endurance athletes. This study examined the effects of an inspiratory muscle training protocol (IMT) on resting pulmonary function, end-exercise arterial oxygen saturation and performance in hypoxemic rowers. Twenty male and sixteen female well-trained hypoxemic rowers were divided into four groups: IMT-male, control-male, IMT-female and control-female. The IMT groups, additionally to the regular training, performed IMT (30 min/day, 5 times/week, 6 weeks). Before and after training, groups underwent an incremental rowing test, a 2000-m time trial and a 5-min “all-out” race. IMT increased respiratory strength in the IMT-male (135 ± 31 vs. 180 ± 22 cmH2O) and IMT-female (93 ± 19 vs. 142 ± 22 cmH2O) (P < 0.05). The IMT-female group exhibited lower EIAH and improved rowing performance in the 2000-m time trial (487 ± 32 vs. 461 ± 34 sec) and in the 5-min “all-out” test (1,285 ± 28 vs. 1,310 ± 36m) (P < 0.05). IMT protocol improved performance in IMT-male only in the 5-min test (1,651 ± 31 vs. 1,746 ± 37m) (P < 0.05). IMT may be a useful tool for increasing respiratory strength and enhancing performance in hypoxemic rowers, especially for women.

Abbreviations: EIAH: Exercise-induced arterial hypoxemia; IMT: inspiratory muscle training protocol; PaO2: partial pressure of arterial oxygen; SaO2: arterial oxyhemoglobin saturation; VO2max: maximal oxygen consumption; [(A-a)DO2]: alveolar-to-arterial oxygen difference; VA/Q: ventilation-perfusion inequality/mismatching; PImax: maximal inspiratory pressure; BMI: body mass index; BSA: body surface area; FVC: vital capacity; FEV1: forced expiratory volume in 1 sec; VCin: vital capacity; MVV12: maximal voluntary ventilation in 12 sec  相似文献   

8.
Inspiratory muscle fatigue may occur in as little as 6 min during high-intensity spontaneously breathing exercise. The aims of this study were to determine whether inspiratory muscle fatigue occurs during swimming exercise and whether inspiratory muscle strength differs between the supine and standing body positions. Seven competitive swimmers were recruited to perform a single 200 m front-crawl swim, corresponding to 90-95% of race pace. Inspiratory muscle strength was measured at residual volume using a hand-held mouth pressure meter that measured maximal inspiratory pressure in the upright and supine positions. At baseline, maximal inspiratory pressure in the supine position was significantly lower than maximal inspiratory pressure in the upright position (112 +/- 20.4 and 133 +/- 16.7 cmH2O, respectively; P < or = 0.01). Post-exercise maximal inspiratory pressure in the supine position (80 +/- 15.7 cmH2O) was significantly lower than baseline maximal inspiratory pressure in the supine position (P < or = 0.01). The results indicate that a single 200 m front-crawl swim corresponding to 90-95% of race pace was sufficient to induce inspiratory muscle fatigue in less than 2.7 min. Furthermore, although diaphragm muscle length is optimized when supine, our results indicate that the force output of the diaphragm and inspiratory accessory muscles is greater when upright than when supine.  相似文献   

9.
Endurance running performance in athletes with asthma   总被引：1，自引：0，他引：1  
Laboratory assessment was made during maximal and submaximal exercise on 16 endurance trained male runners with asthma (aged 35 +/- 9 years) (mean +/- S.D.). Eleven of these asthmatic athletes had recent performance times over a half-marathon, which were examined in light of the results from the laboratory tests. The maximum oxygen uptake (VO2max) of the group was 61.8 +/- 6.3 ml kg-1 min-1 and the maximum ventilation (VEmax) was 138.7 +/- 24.7 l min-1. These maximum cardio-respiratory responses to exercise were positively correlated to the degree of airflow obstruction, defined as the forced expiratory volume in 1 s (expressed as a percentage of predicted normal). The half-marathon performance times of 11 of the athletes ranged from those of recreational to elite runners (82.4 +/- 8.8 min, range 69-94). Race pace was correlated with VO2max (r = 0.863, P less than 0.01) but the highest correlation was with the running velocity at a blood lactate concentration of 2 mmol l-1 (r = 0.971, P less than 0.01). The asthmatic athletes utilized 82 +/- 4% VO2max during the half-marathon, which was correlated with the %VO2max at 2 mmol l-1 blood lactate (r = 0.817, P less than 0.01). The results of this study suggest that athletes with mild to moderate asthma can possess high VO2max values and can develop a high degree of endurance fitness, as defined by their ability to sustain a high percentage of VO2max over an endurance race. In athletes with more severe airflow obstruction, the maximum ventilation rate may be reduced and so VO2max may be impaired. The athletes in the present study have adapted to this limitation by being able to sustain a higher %VO2max before the accumulation of blood lactate, which is an advantage during an endurance race. Therefore, with appropriate training and medication, asthmatics can successfully participate in endurance running at a competitive level.  相似文献   

10.
The respiratory time and flow profile at volitional exercise termination   总被引：1，自引：0，他引：1  
In this study, we examine the effect of exercise on the time and flow characteristics of the respiratory cycle profile at the point of volitional exercise termination. Eight males (mean age 29 years, s = 10; body mass 74 kg, s = 7; height 1.75 m, s = 0.04) undertook a cycle test to volitional exhaustion on a cycle ergometer, which allowed peak oxygen uptake (VO(2peak)) to be measured (mean 51 ml x kg(-1) x min(-1), s = 7). At a later date, two sub-maximal tests to volitional exhaustion were completed in a random order at 76% (s = 6) and 86% VO(2peak) (s = 7). As expected, the magnitude of the respiratory flow and time characteristics varied with the three exercise intensities, as did the point of exercise termination and terminal ventilation rates, which varied from 7 to 27 min and 112 to 132 litres x min(-1) respectively. More importantly, however, at exercise termination some of the characteristics were similar, particularly the breathing frequency (at termination 49 breaths x min(-1)), the ratio between inspiration and total breath time (0.5), and the later occurrence of peak inspiratory flow (0.24-0.48 s). The coincident unity of these time and flow profile characteristics at exercise termination illustrates how the integration of timing and flow during breathing influence exercise capacity in non-elite athletes.  相似文献   

11.
The purpose of the present study was to assess fitness and running performance in a group of recreational runners (men, n = 18; women, n = 13). 'Fitness' was determined on the basis of their physiological and metabolic responses during maximal and submaximal exercise. There were strong correlations between VO2 max and treadmill running speeds equivalent to blood lactate concentrations of 2 mmol l-1 (V-2 mM) or 4 mmol l-1 (V-4 mM), 'relative running economy' and 5 km times (r = -0.84), but modest and non-significant correlations between muscle fibre composition and running performance. The results of the submaximal exercise tests suggested that the female runners were as well trained as the male runners. However, the men still recorded faster 5 km times (19.20 +/- 1.97 min vs 20.97 +/- 1.70 min; P less than 0.05). Therefore the of the present study suggest that the faster performance times recorded by the men were best explained by their higher VO2 max values, rather than their training status per se.  相似文献   

12.
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   

13.
Inspiratory muscle fatigue may occur in as little as 6 min during high-intensity spontaneously breathing exercise. The aims of this study were to determine whether inspiratory muscle fatigue occurs during swimming exercise and whether inspiratory muscle strength differs between the supine and standing body positions. Seven competitive swimmers were recruited to perform a single 200 m front-crawl swim, corresponding to 90-95% of race pace. Inspiratory muscle strength was measured at residual volume using a hand-held mouth pressure meter that measured maximal inspiratory pressure in the upright and supine positions. At baseline, maximal inspiratory pressure in the supine position was significantly lower than maximal inspiratory pressure in the upright position (112±20.4 and 133±16.7 cmH2O, respectively; P?0.01). Post-exercise maximal inspiratory pressure in the supine position (80±15.7 cmH2O) was significantly lower than baseline maximal inspiratory pressure in the supine position (P?0.01). The results indicate that a single 200 m front-crawl swim corresponding to 90-95% of race pace was sufficient to induce inspiratory muscle fatigue in less than 2.7 min. Furthermore, although diaphragm muscle length is optimized when supine, our results indicate that the force output of the diaphragm and inspiratory accessory muscles is greater when upright than when supine.  相似文献   

14.
The purpose of this study was to assess the validity of predicting the maximal oxygen uptake (VO2(max)) of sedentary men from sub-maximal VO2 values obtained during a perceptually regulated exercise test. Thirteen healthy, sedentary males aged 29-52 years completed five graded exercise tests on a cycle ergometer. The first and fifth test involved a graded exercise test to determine VO2(max). The two maximal graded exercise tests were separated by three sub-maximal graded exercise tests, perceptually regulated at 3-min RPE intensities of 9, 11, 13, 15, and 17 on the Borg ratings of perceived exertion (RPE) scale, in that order. After confirmation that individual linear regression models provided the most appropriate fit to the data, the regression lines for the perceptual ranges 9-17, 9-15, and 11-17 were extrapolated to RPE 20 to predict VO2(max). There were no significant differences between VO2(max) values from the graded exercise tests (mean 43.9 ml x kg(-1) x min(-1), s = 6.3) and predicted VO2(max) values for the perceptual ranges 9-17 (40.7 ml x kg(-1) x min(-1), s = 2.2) and RPE 11-17 (42.5 ml x kg(-1) x min(-1), s = 2.3) across the three trials. The predicted VO2(max) from the perceptual range 9-15 was significantly lower (P < 0.05) (37.7 ml x kg(-1) x min(-1), s = 2.3). The intra-class correlation coefficients between actual and predicted VO2(max) for RPE 9-17 and RPE 11-17 across trials ranged from 0.80 to 0.87. Limits of agreement analysis on actual and predicted VO2 values (bias +/- 1.96 x S(diff)) were 3.4 ml x kg(-1) x min(-1) (+/- 10.7), 2.4 ml x kg(-1) x min(-1) (+/- 9.9), and 3.7 ml x kg(-1) x min(-1) (+/- 12.8) (trials 1, 2, and 3, respectively) of RPE range 9-17. Results suggest that a sub-maximal, perceptually guided graded exercise test provides acceptable estimates of VO2(max) in young to middle-aged sedentary males.  相似文献   

15.
Abstract

Respiratory muscle fatigue has been reported following short bouts of high-intensity exercise, and prolonged, moderate-intensity exercise, as evidenced by decrements in inspiratory and expiratory mouth pressures. However, links to functionally relevant outcomes such as breathing effort have been lacking. The present study examined dyspnoea and leg fatigue during a treadmill marathon in nine experienced runners. Maximal inspiratory and expiratory pressure, peak inspiratory and expiratory flow, forced vital capacity, and forced expiratory volume in one second were assessed before, immediately after, and four and 24 hours after a marathon. During the run, leg effort was rated higher than respiratory effort from 18 through 42 km (P < 0.05). Immediately after the marathon, there were significant decreases in maximal inspiratory pressure and peak inspiratory flow (from 118 ± 20 cm H2O and 6.3 ± 1.4 litres · s?1 to 100 ± 22 cm H2O and 4.9 ± 1.5 litres · s?1 respectively; P < 0.01), while expiratory function remained unchanged. Leg maximum voluntary contraction force was significantly lower post-marathon. Breathing effort correlated significantly with leg fatigue (r = 0.69), but not inspiratory muscle fatigue. Our results confirm that prolonged moderate-intensity exercise induces inspiratory muscle fatigue. Furthermore, they suggest that the relative intensity of inspiratory muscle work during exercise makes some contribution to leg fatigue.  相似文献   

16.
The aim of this study was to predict indoor rowing performance in 12 competitive female rowers (age 21.3 +/- 3.6 years, height 1.68 +/- 0.54 m, body mass 67.1 +/- 11.7 kg; mean +/- s) using a 30 s rowing sprint, maximal oxygen uptake and the blood lactate response to submaximal rowing. Blood lactate and oxygen uptake (VO2) were measured during a discontinuous graded exercise test on a Concept II rowing ergometer incremented by 25 W for each 2 min stage; the highest VO2 measured during the test was recorded as VO2max (mean = 3.18 +/- 0.35 l.min-1). Peak power (380 +/- 63.2 W) and mean power (368 +/- 60.0 W) were determined using a modified Wingate test protocol on the Concept II rowing ergometer. Rowing performance was based on the results of the 2000 m indoor rowing championship in 1997 (466.8 +/- 12.3 s). Laboratory testing was performed within 3 weeks of the rowing championship. Submitting mean power (Power), the highest and lowest five consecutive sprint power outputs (Maximal and Minimal), percent fatigue in the sprint test (Fatigue), VO2max (l.min-1), VO2max (ml.kg-1.min-1), VO2 at the lactate threshold, power at the lactate threshold (W), maximal lactate concentration, lactate threshold (percent VO2max) and VEmax (l.min-1) to a stepwise multiple regression analysis produced the following model to predict 2000 m rowing performance: Time2000 = -0.163 (Power) -14.213.(VO2max l.min-1) +0.738.(Fatigue) 7.259 (R2 = 0.96, standard error = 2.89). These results indicate that, in the women studied, 75.7% of the variation in 2000 m indoor rowing performance time was predicted by peak power in a rowing Wingate test, while VO2max and fatigue during the Wingate test explained an additional 12.1% and 8.2% of the variance, respectively.  相似文献   

17.
Clear criteria for maximal oxygen consumption (VO2max) determination in youth are not available, and no studies have examined this issue in girls. Our purpose was to determine whether different peak heart rate (HRpeak) and peak respiratory exchange ratio (RERpeak) cut points affect girls' (N = 453; M age = 13.3 years, SD = .1) VO2max during a maximal treadmill test. A multivariate analysis of variance revealed VO2max (ml kg(-1) min(-1) differed significantly among HRpeak, 180-189 b min(-1) = 34 (SD = .8), 190-194 bmin(-1) = 35 (SD = .9), 195-199 b min(-1) = 38 (SD = .8), 200-204 b min(-1) = 40 ml kg1 x min(-1) (SD = .8), and > or = 205 bmin(-1) = 42 ml kg1 x min(-1) (SD = .7) but not RERpeak. In studies where evidence of a VO2 plateau was examined, peak oxygen consumption (VO2peak) did not differ between plateau and no-plateau groups. Although our results suggest the association between lower VO2peak and lower peak heart rate is a true cardiovascular limit to aerobic energy production, we cannot rule out participant effort.  相似文献   

18.
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   

19.
The aims of the present study were to assess the maximal oxygen uptake and body composition of adult Chinese men and women, and to determine how these variables relate to age. The cross-sectional sample consisted of 196 men and 221 women aged 20 - 64 years. Maximal oxygen uptake (VO2max) was determined by indirect calorimetry during a maximal exercise test on an electrically braked cycle ergometer. The correlations between VO2max and fat mass were -0.52 in men and -0.58 in women. Linear regression defined the cross-sectional age-related decline in VO2max as 0.35 ml kg(-1) min(-1) year(-1) in men and 0.30 ml kg(-1) min(-1) year(-1) in women. Multiple regression analysis showed that more than 50% of this cross-sectional decline in VO2max was due to fat mass, lean mass, and age. Adding fat mass and lean mass to the multiple regression models reduced the age regression mass from 0.35 to 0.24 ml kg(-1) min(-1) year(-1) in men and from 0.30 to 0.15 ml kg(-1) min(-1) year(-1) in women. We conclude that age, fat mass, and lean mass are independent determinants of maximal oxygen uptake in Chinese adults.  相似文献   

20.
The aim of the present study was to examine the effect of ingesting 75 g of glucose 45 min before the start of a graded exercise test to exhaustion on the determination of the intensity that elicits maximal fat oxidation (Fatmax). Eleven moderately trained individuals (VO2max: 58.9 +/- 1.0 ml x kg(-1) x min(-1); mean +/- sx), who had fasted overnight, performed two graded exercise tests to exhaustion, one 45 min after ingesting a placebo drink and one 45 min after ingesting 75 g of carbohydrate in the form of glucose. The tests started at 95 W and the workload was increased by 35 W every 3 min. Gas exchange measures and heart rate were recorded throughout exercise. Fat oxidation rates were calculated using stoichiometric equations. Blood samples were collected at rest and at the end of each stage of the test. Maximal fat oxidation rates decreased from 0.46 +/- 0.06 to 0.33 +/- 0.06 g min(-1) when carbohydrate was ingested before the start of exercise (P < 0.01). There was also a decrease in the intensity which elicited maximal fat oxidation (60.1 +/- 1.9% vs 52.0+3.4% VO2max) after carbohydrate ingestion (P < 0.05). Maximal power output was higher in the carbohydrate than in the placebo trial (346 +/- 12 vs 332 +/- 12 W) (P < 0.05). In conclusion, the ingestion of 75 g of carbohydrate 45 min before the onset of exercise decreased Fatmax by 14%, while the maximal rate of fat oxidation decreased by 28%.  相似文献   

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