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1.
Abstract

Energy turnover was assessed in two conditions of mixed ultra-endurance exercise. In Study 1, energy expenditure and intake were measured in nine males in a laboratory over 24 h. In Study 2, energy expenditure was assessed in six males during an 800-km Adventure race (mean race time 152.5 h). Individual correlations between heart rate and oxygen uptake ([Vdot]O2) were established during pre-tests when kayaking, cycling, and running. During exercise, energy expenditure was estimated from continuous heart rate recordings. Heart rate and [Vdot]O2 were measured regularly during fixed cycling work rates to correct energy expenditure for drift in oxygen pulse. Mean energy expenditure was 18,050 ± 2,390 kcal (750 ± 100 kcal · h?1) and 80,000 ± 18,000 kcal (500 ± 100 kcal · h?1) in Study 1 and Study 2 respectively, which is higher than previously reported. Energy intake in Study 1 was 8,450 ± 1,160 kcal, resulting in an energy deficit of 9,590 ± 770 kcal. Body mass decreased in Study 1 (?2.3 ± 0.8 kg) but was unchanged in Study 2. Fat mass decreased in Study 2 (?2.3 ± 1.5 kg). In Study 1, muscle glycogen content decreased by only 60%. Adventure racing requires a high energy expenditure, with large inter-individual variation. A large energy deficit is caused by inadequate energy intake, possibly due to suppressed appetite and gastrointestinal problems. The oxygen pulse, comparing start to 12 h of exercise and beyond, increased by 10% and 5% in Study 1 and Study 2 respectively. Hence, estimations of energy expenditure from heart rate recordings should be corrected according to this drift.  相似文献   

2.
Abstract

This study examined the accuracy of a new device (Caltrac) in estimating energy expenditure via acceleration measurements. Energy expenditure of 20 high school students during basketball class activity (average length = 37 min) was estimated using the Caltrac, heart rate recording, and video analysis. Heart rate recording and video analysis estimates of energy expenditure were determined from heart rate, caloric expenditure curves, and an activity rating scale, respectively. The following estimates of caloric expenditure (M ± SD) were found: heart rate recording = 196 ±73 > Caltrac = 163 ±49 > film analysis = 123 ± 30 kcal (p < .05). Laboratory simulations of the basketball activity revealed that the Caltrac energy expenditure was not significantly different from the actual energy expenditure (p > .05). The heart rate recording and video analysis estimates of energy expenditure were significantly (p < .05) higher and lower, respectively, than the actual energy expenditure. The Caltrac is a lightweight, low-cost device that provides a relatively accurate estimate of energy expenditure in free-ranging activities, such as basketball.  相似文献   

3.
This study compared the physiological responses (oxygen consumption and energy expenditure) of Nordic Walking to regular walking under field-testing conditions. Eleven women (M age = 27.1 years, SD = 6.4) and 11 men (M age = 33.8 years, SD = 9.0) walked 1,600 m with and without walking poles on a level, 200-m track. For women, Nordic Walking resulted in increased oxygen consumption (M = 14.9 ml x kg(-1) x min(-1), SD = 3.2 vs. M = 1 7.9 ml x kg(-1) min(-1), SD = 3.5; p < .001), caloric expenditure (M = 4.6 kcal x min(-1), SD = 1.2 vs. M = 5.4 kcal x min(-1), SD = 1.2; p < .001), and heart rate (M = 113.7 bpm, SD = 12.0 vs. M = 118.7 bpm, SD = 14.8; p < .05) compared to regular walking. For men, Nordic Walking resulted in increased oxygen consumption (M = 12.8 ml x kg(-1) min(-1), SD = 1.8 vs. M = 15.5, SD =3.4 ml x kg(-1) min(-1); p < .01), caloric expenditure (M = 5.7 kcal x min(-1), SD = 1.3 vs. M = 6.9 kcal x min(-1), SD = 1.8; p < .001), and heart rate (M = 101.6 bpm, SD = 12.0 bpm vs. M = 109.8 bpm, SD = 14.7; p < .01) compared to regular walking. Nordic Walking, examined in the field, results in a significant increase in oxygen use and caloric expenditure compared to regular walking, without significantly increasing perceived exertion.  相似文献   

4.
ABSTRACT

Prior exercise can negatively affect movement economy of a subsequent task. However, the impact of cycling exercise on the energy cost of subsequent running is difficult to ascertain, possibly because of the use of different methods of calculating economy. We examined the influence of a simulated cycling bout on running physiological cost (running economy, heart rate and ventilation rates) and perceptual responses (ratings of perceived exertion and effort) by comparing two running bouts, performed before and after cycling using different running economy calculation methods. Seventeen competitive male triathletes ran at race pace before and after a simulated Olympic-distance cycling bout. Running economy was calculated as V?O2 (mL?kg?1?min?1), oxygen cost (EO2, mL?kg?1?m?1) and aerobic energy cost (Eaer, J?kg?1?m?1). All measures of running economy and perceptual responses indicated significant alterations imposed by prior cycling. Despite a good level of agreement with minimal bias between calculation methods, differences (p < 0.05) were observed between Eaer and both V?O2 and EO2. The results confirmed that prior cycling increased physiological cost and perceptual responses in a subsequent running bout. It is recommended that Eaer be calculated as a more valid measure of running economy alongside perceptual responses to assist in the identification of individual responses in running economy following cycling.  相似文献   

5.
Abstract

Two studies examined the effects of the experimenter on heart rate (HR), rating of perceived exertion (RPE), and time to voluntary exhaustion on a graded treadmill test in college students. The first study determined the effects of the gender and race of the tester on black and white subjects of both sexes. Four testers (black female—BFT, white female—WFT, black male—BMT, and white male—WMT) tested 5 subjects of each gender and race. Differences based on gender and race were determined by a 2 × 2 × 2 × 2 ANOVA. The second study dealt with the tester/subject relationship. One tester tested 20 subjects. Ten were his friends (5 males, 5 females) and 10 (5 males, 5 females) did not know him. Differences were determined by 2 × 2 ANOVA. In both studies, the female subjects had poorer performance than the males. HR during moderate and heavy exercise was not affected by the race and gender of the tester or the tester/subject relationship. For time to exhaustion, white female subjects (WFS) exercised longer when being tested by a female but black female subjects (BFS) had a longer total time with male testers. Significant interactions occurred for HR at rest and at various times during light work for both studies. There were also significant interactions for RPE at various stages of light, moderate and heavy exercise for both studies. For subjects unaccustomed to exercise testing, it appears that the effects of the race and gender of the tester and the tester/subject relationship predominate at rest and during light work. Fewer effects are observed during moderate and heavy work. Many of the results in these studies are consistent with societal roles and expectations for males and females, blacks and whites. A consistent testing environment can minimize the influence of extrinsic testing variables.  相似文献   

6.
Abstract

The purpose of this study was to investigate the influence of a warm environment on thermoregulation and energy expenditure during sub-maximal prolonged exercise in humans. Six healthy male subjects cycled for 120?min at an intensity of 60% maximal oxygen uptake (Vo2max) at three environmental temperatures (10°C, CT; 20°C, MT; and 30°C, WT). Although oxygen uptake at WT showed a significantly lower value compared to those at MT and CT, no significant differences of respiratory exchange ratio were observed among the three environmental trials. A remarkable decrease in total energy expenditure during the 120-min exercise at WT was observed in comparison with those at MT and CT (p<0.05). Changes in rectal temperature, mean skin temperature, and mean body temperature at WT were significantly higher than those at both MT and CT. Although increases in mean body temperature from rest every five minutes during exercise were not different among three environmental temperatures, mean energy expenditures every five minutes at WT were lower compared with those at MT and CT (p<0.05). These results suggest that the increase in energy expenditure for physical exertion is substantially reduced during prolonged sub-maximal exercise in a warm environment. This acute alteration in the energy metabolism may contribute to inhibition of excess heat production and enable prolonged exercise in a warm environment.  相似文献   

7.
We measured the effects of stride rate, resistance, and combined arm-leg use on energy expenditure during elliptical trainer exercise and assessed the accuracy of the manufacturer's energy expenditure calculations. Twenty-six men and women (M age = 29 years, SD = 8; M body weight = 73. 0 kg, SD = 15.2) participated. Twenty-two participants performed two tests, one without the arm poles (leg-only) and the other with arm poles (combined arm-leg). The other 4 participants performed one test without the arm poles. Both tests consisted of six 5-min stages (two stride rates, 110 and 134 stridesmin-1, and three resistance settings: 2, 5, and 8). Steady-state oxygen uptake (VO2), minute ventilation (VE), heart rate (HR) and rating of perceived exertion (RPE) were measured. Repeated measures analysis of variance determined higher (p <. 001) VO2, VE, and RPE, but not HR, during combined arm-leg versus leg-only exercise at any given intensity. Increases in stride rate and resistance increased VO2, VE, RPE, and HR with the greatest effect on VE and HR from Levels 5 to 8. The manufacturer's calculated energy expenditure was overestimated during both tests. Although the oxygen cost for elliptical trainer exercise was calculated to be approximately 0.1 mlxkg(-1) per stride and 0.7 mlxkg(-1) min-1 per resistance level, VO2 varied widely among individuals, possibly due to differences in experience using the elliptical trainer gender, and body composition. The elliptical trainer offers (a) a variety of intensities appropriate for most individuals and (b) both arm and leg exercise. Due to the wide variability in VO2, predicting the metabolic cost during elliptical trainer exercise for an individual is not appropriate.  相似文献   

8.
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   

9.
Abstract

The purpose of this study was to examine the accuracy of the ePulse Personal Fitness Assistant, a forearm-worn device that provides measures of heart rate and estimates energy expenditure. Forty-six participants engaged in 4-minute periods of standing, 2.0 mph walking, 3.5 mph walking, 4.5 mph jogging, and 6.0 mph running. Heart rate and energy expenditure were simultaneously recorded at 60-second intervals using the ePulse, an electrocardiogram (EKG), and indirect calorimetry. The heart rates obtained from the ePulse were highly correlated (intraclass correlation coefficients [ICCs] ≥0.85) with those from the EKG during all conditions. The typical errors progressively increased with increasing exercise intensity but were <5 bpm only during rest and 2.0 mph. Energy expenditure from the ePulse was poorly correlated with indirect calorimetry (ICCs: 0.01–0.36) and the typical errors for energy expenditure ranged from 0.69–2.97 kcal · min?1, progressively increasing with exercise intensity. These data suggest that the ePulse Personal Fitness Assistant is a valid device for monitoring heart rate at rest and low-intensity exercise, but becomes less accurate as exercise intensity increases. However, it does not appear to be a valid device to estimate energy expenditure during exercise.  相似文献   

10.
Abstract

The effects of breathing 100% oxygen on resting, exercise, and recovery oxygen consumptions, pulmonary ventilation volumes, and heart rates were observed on six highly conditioned male athletes. The subjects rode a bicycle ergometer at a heavy work load for five minutes, breathing either normal air or medical oxygen. Ventilation volumes were determined by the open-circuit Douglas bag method, measuring inspired and expired volumes. Gas samples were analyzed for nitrogen and oxygen concentrations on Van Slyke and Beckman gas analyzers, and heart rates were recorded via a telemetry-electrocardiograph system. The results indicated a substantial increase in resting oxygen consumption, a decrease in resting ventilation volume, a marked decline in exercise and recovery ventilation volumes, and an insignificant lowering of the energy cost of exercise during the oxygen experiments. No appreciable differences were noted in heart rates between the oxygen and air experiments.  相似文献   

11.
ABSTRACT

Purpose: The purpose of this study was to evaluate the agreement of five commercially available accelerometers in estimating energy expenditure while performing an acute bout of high-intensity functional training (HIFT). Methods: Participants (n = 47; average age: 28.5 ± 11.6 years) consisted of recreationally active, healthy adults. Each participant completed a session of HIFT: a 15-minute workout consisting of 12 repetitions each of air-squats, sit-ups, push-ups, lunges, pull-ups, steps-ups, and high-knees; performed circuit-style by completing as many rounds as possible. During this session, each participant wore the Cosmed K4b2 portable metabolic analyzer (PMA) and five different accelerometers (ActiGraph GT3X, Nike Fuelband, Fitbit One, Fitbit Charge HR, and Jawbone UP Move). Results: Four of the five activity trackers reported lower (p < .05) total EE values compared to the PMA during the acute bout of HIFT. The waist-mounted device (ActiGraph, 182.55 ± 37.93 kcal) was not significantly different from, and most closely estimated caloric expenditure compared to the PMA (144.99 ± 37.13 kcal) (p = .056). A repeated-measures ANOVA showed that all activity trackers were significantly different from the reference measure (PMA) (p < .05). Systematic relative agreement between the activity trackers was calculated, exhibiting a significant ICC = 0.426 (F [46,230] = 5.446 [p < .05]). Conclusion: The wrist- and hip-mounted activity trackers did not accurately assess energy expenditure during HIFT exercise. With the exception of the ActiGraph GT3X, the remaining four activity trackers showed inaccurate estimates of the amount of kilocalories expended during the HIFT exercise bout compared to the PMA.  相似文献   

12.
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   

13.
We measured the effects of stride rate, resistance, and combined arm-leg use on energy expenditure during elliptical trainer exercise and assessed the accuracy of the manufacturer's energy expenditure calculations. Twenty-six men and women (M age = 29 years, SD = 8; M body weight = 73.0 kg, SD = 15.2) participated. Twenty-two participants performed two tests, one without the arm poles (leg-only) and the other with arm poles (combined arm-leg). The other 4 participants performed one test without the arm poles. Both tests consisted of six 5-min stages (two stride rates, 110 and 134 strides.min-1, and three resistance settings: 2, 5, and 8). Steady-state oxygen uptake (VO2), minute ventilation (VE), heart rate (HR) and rating of perceived exertion (RPE) were measured. Repeated measures analysis of variance determined higher (p < .001) VO2, VE, and RPE, but not HR, during combined arm-leg versus leg-only exercise at any given intensity. Increases in stride rate and resistance increased VO2, VE, RPE, and HR with the greatest effect on VE and HR from Levels 5 to 8. The manufacturer's calculated energy expenditure was overestimated during both tests. Although the oxygen cost for elliptical trainer exercise was calculated to be approximately 0.1 ml.kg-1 per stride and 0.7 ml.kg-1.min-1 per resistance level, VO2 varied widely among individuals, possibly due to differences in experience using the elliptical trainer, gender, and body composition. The elliptical trainer offers (a) a variety of intensities appropriate for most individuals and (b) both arm and leg exercise. Due to the wide variability in VO2, predicting the metabolic cost during elliptical trainer exercise for an individual is not appropriate.  相似文献   

14.
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   

15.
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   

16.
BackgroundPoor sleep quality is associated with adverse effects on health outcomes. It is not clear whether exercise can improve sleep quality and whether intensity of exercise affects any of the effects.MethodsFifteen healthy, non-obese (body mass index = 24.4 ± 2.1 kg/m2, mean ± SD), sedentary (<20 min of exercise on no more than 3 times/week) older women (66.1 ± 3.9 years) volunteered for the study. Peak oxygen consumption (VO2peak) was evaluated using a graded exercise test on a treadmill with a metabolic cart. Following a 7-day baseline period, each participant completed two exercise sessions (separated by 1 week) with equal caloric expenditure, but at different intensities (60% and 45% VO2peak, sequence randomized) between 9:00 and 11:00 am. A wrist ActiGraph monitor was used to assess sleep at baseline and two nights following each exercise session.ResultsThe average duration of the exercise was 54 and 72 min, respectively at 60% (moderate-intensity) and 45% VO2peak (light-intensity). Wake time after sleep onset was significantly shorter (p = 0.016), the number of awakenings was less (p = 0.046), and total activity counts were lower (p = 0.05) after the moderate-intensity exercise compared to baseline no-exercise condition.ConclusionOur data showed that a single moderate-intensity aerobic exercise session improved sleep quality in older women.  相似文献   

17.
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18.
BackgroundIncreasing caloric expenditure in physical education is considered an effective school-based approach to addressing the child obesity epidemic. This study was designed to determine synergistic influences of student characteristics and lesson factors on caloric expenditure in elementary and middle school physical education.MethodsThe study used a multi-level design. Level-1 factors included personal characteristics: age, gender, and body mass index. Level-2 factors included lesson length, content, and school level. Based on the Center for Disease Control and Prevention age–gender adjusted growth chart, students in 87 classes from 14 elementary and 15 middle schools were pre-screened into “Overweight”, “Healthy weight”, or “Thin” groups. One boy and one girl were randomly selected from each group in each class as data providers (264 elementary and 294 middle school students). Caloric expenditure was measured in 243 physical education lessons using accelerometers.ResultsAnalysis of variance revealed and hierarchical linear modeling confirmed separate age by body mass index, age by gender, and content by lesson–length interaction effects, suggesting that the personal and lesson factors influenced caloric expenditure independently. Older male and heavier students burned more calories in all lessons. Students burned more calories in 45–60 min sport skill or fitness lessons than in shorter (30 min) or longer (75–90 min) game or multi-activity lessons.ConclusionsThe hypothesized cross-level interaction was not observed in the data. Caloric expenditure can be optimized in 45–60 min sport skill or fitness development lessons. It can be recommended that schools adopt 45–60 min lesson length and provide skill and fitness development tasks in physical education to maximize caloric expenditure.  相似文献   

19.
Whole-body energy expenditure for heavy/severe exercise is currently accounted for by either: (1) anaerobic and oxygen uptake measures during exercise where recovery energy expenditure is omitted; or (2) oxygen uptake during, and an EPOC (excess post-exercise oxygen consumption), measure following exercise where substrate level phosphorylation during exercise is considered part of EPOC. Simultaneous direct/indirect calorimetry enabled us to determine if a thermodynamic reversal (i.e. heat consumption) takes place as the highly exothermic pyruvate to lactate reaction proceeds in the opposite direction. Reversibility implies that oxygen uptake (e.g. EPOC) can indeed account for rapid glycolytic ATP production regardless if lactate is formed or not (e.g. 1.2 g glucose catabolism = 20.9 kJ x l O2(-1)). Cultured hybrid cells and mouse cardiac muscle fibres were utilized in simultaneous calorimetry and respirometry experiments where pyruvate or lactate was predominantly oxidized. The calorimetric to respiratory ratio was determined using heat flux (pW x cell(-1)) and oxygen flux (pmol x s(-1) cell(-1)) measures. Ten cell experiments gave calorimetric to respiratory ratios that showed no statistical difference (P= 0.97) whether cells respired predominantly on lactate (-516+/-53 kJ x mol O2(-1)) or pyruvate (- 517+/-89 kJ x mol O2(-1)). In three cardiac preparations, the calorimetric to respiratory ratio was -502+/-15 kJ x mol O2(-1) for lactate and -506+/-47 kJ x mol O2(-1) for pyruvate, again a non-significant difference (P= 0.91). Heat consumption did not occur during lactate oxidation. These results suggest that rapid glycolytic ATP and lactate production, and lactate oxidation, are both independently associated with heat production and thus represent separate and additive components to the measurement of total energy expenditure for exercise and recovery.  相似文献   

20.
Abstract

This study examined the effect of shoulder angle and gender on physiological and perceptual responses during incremental peak arm ergometry. Healthy adults (nine males, seven females) volunteered for the study and completed an incremental arm ergometry test on two separate occasions at two different shoulder angles (90° and 45°). Initial work rate was set at 16 W · min?1 and was increased progressively until exhaustion. Cardiorespiratory and perceptual responses were recorded at the end of each minute and compared using separate three-way (position × work rate × gender) repeated-measures analyses of variance. The systematic bias of peak responses was examined using separate two-way (position × gender) analyses of variance, while reproducibility of these parameters was explored using intraclass correlation coefficients, measurement bias/ratio, and 95% ratio limits of agreement. Despite a significantly greater peak heart rate for the 45° position, cardiorespiratory and perceptual responses were similar at peak exercise for both positions. Peak values for all variables, although similar, demonstrated similar and large inter-test variability for men and women. Reduction of the shoulder joint angle to 45° did not enhance peak work rate and peak oxygen consumption during seated upper body exercise. Due to the large inter-test variability, arm ergometry should be conducted using the same seated position.  相似文献   

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