Physiological response to water aerobics.

Heart rate (HR) and oxygen uptake (VO2) measured during water aerobics (WA) were compared to maximal values obtained during an incremental treadmill test to assess the energy demand and potential cardiorespiratory (CR) training effects of WA. Sixteen college-age females served as subjects (mean +/- SD = 20.4 +/- 1.6 years). WA elicited a mean HR of 162 b.min-1 and a mean VO2 of 18.4 ml.kg-1.min-1 which represented 74% of HR reserve, 82% of maximal HR, and 48% of VO2 max. Average caloric expenditure was 5.7 kcal.min-1. HR values for WA were consistent with guidelines established by the American College of Sports Medicine for developing and maintaining CR fitness in healthy adults. However, the VO2 fell just below the recommended minimum threshold level. It was concluded that WA may provide an attractive alternative to traditional modes of exercise for improving CR fitness, however, HR measures may overestimate the metabolic intensity of the exercise.     

Energy cost and energy sources of ball routine in rhythmic gymnasts

The energy cost and the different energy sources of competitive rhythmic ball-routines were assessed in nine young elite rhythmic gymnasts (13-16 years of age). The overall energy requirement of ball exercise (VO2eq) was obtained by adding the amount of VO2 during exercise above resting (VO2ex) to the VO2 up to the fast component of recovery (VO2al) and to the energy equivalent of peak blood lactate accumulation (VO2la-) of recovery. The lactate (La) curve up to 25 minutes of recovery always showed La peaks at 3 min after exercise (4.0 +/- 0.4 mmol/l) and values still above rest at 25 min (2.3 +/- 0.5 mmol/l). Although ball routines were short in duration (90 s), the metabolic power requirement was 1.1 times higher than the subject's VO2max. The energy cost (VO2eq) amounted to 81 +/- 5 ml x kg(-1). Higher fractions of VO2eq were VO2ex 49% and VO2al 42%, while the remaining 9% was due to VO2la-. The aerobic source resulted in the most utilized system due to the subjects' high VO2max (52.7 ml x kg(-1) x min(-1)) and anaerobic threshold (LT = 84.4%). The HR and the peak lactate values of ball routine were similar to the values recorded at LT step during treadmill test. Although the HR and VO2 values were significantly correlated (during pre-exercise, exercise, and fast recovery), the exercise intensity derived from HR Kanvonen method during ball routine did not correspond to the % of VO2max.     

A comparison of the shuttle and 6 minute walking tests with measured peak oxygen consumption in patients with heart failure

This study investigated the use of an incremental, externally-paced 10 m shuttle walk test (SWT) as an objective, reliable and predictive test of functional capacity in patients with heart failure (CHF). The SWT was compared to a 6 minute walk test (6WT) and a maximal symptom-limited treadmill peak oxygen consumption (VO2peak) test. Experiment 1 examined the reproducibility of the SWT. Two SWF trials were performed and distance ambulated (DA), heart rate (HR) and rate of perceived exertion (RPE) results compared. In experiment 2, SWT, 6WT, and VO2 peak tests were performed and HR. RPE and ambulatory VO2 compared. The SWT demonstrated strong test/retest reliability for DA (r = 0.98). HR (r = 0.96) and RPE (r = 0.89). Treadmill VO2 peak was significantly correlated with DA during the SWT (r = 0.83, P < 0.05), but not the 6WT. SWT peak VO2 (18.5 +/- 1.8 ml.kg(-1) x min(-1)) and treadmill VO2 peak (18.3 +/-2.0 ml.kg(-1) x min(-1)) were also highly correlated (r = 0.78, P < 0.05). Conversely, 6WT peak VO2 and treadmill VO2 peak were not significantly correlated. This study suggests the SWT is a reliable, objective test, highly predictive of VO2 peak which may be a more optimal field exercise test than the self paced 6WT.     

Metabolic and cardiorespiratory responses to the performance of Wing Chun and T'ai Chi Chuan exercise

The primary purpose of this study was to examine the metabolic and cardiorespiratory responses to the continuous performance of Wing Chun and T'ai Chi Chuan exercise. No significant differences in VO2max or HRmax obtained during treadmill exercise were found between the practitioners of the two styles. Average values for oxygen uptake (VO2) were 23.3 +/- 7.5 ml.kg-1.min-1 (6.6 METS) and 16.0 +/- 3.9 ml.kg-1.min-1 (4.6 METS) for Wing Chun and T'ai Chi Chuan exercise, respectively. Mean heart rates obtained during exercise were 137 +/- 25 beats.min-1 for Wing Chun and 116 +/- 22 beats.min-1 for T'ai Chi Chuan exercise. These exercise values corresponded to 52.4% of VO2max and 70.5% of HRmax for Wing Chun and only 36.4% of VO2max and 59.8% of HRmax for T'ai Chi Chuan exercise. Thus, only the continuous performance of Wing Chun exercise elicited VO2 and HR responses that would be expected to bring about a cardiorespiratory training effect in subjects with a relatively low initial VO2max. The ventilatory equivalent for oxygen (VE/VO2) obtained during T'ai Chi Chuan exercise (21.7) was significantly lower than for Wing Chun exercise (24.2), suggesting that T'ai Chi practitioners utilize efficient breathing patterns during exercise. Both Wing Chun and T'ai Chi Chuan styles may have a small static component that produces a slightly elevated heart rate relative to metabolic load when compared to traditional aerobic activities. However, the effect was not severe and these forms of exercise should not be considered dangerous for individuals at high risk for cardiovascular disease.     

Effects of a proposed challenge on effort sense and cardiorespiratory responses during exercise.

PURPOSE: Highly trained endurance athletes train and race at relatively high intensities and are often confronted with challenges throughout a running event. The purpose of this study was to examine the effects of the anticipation of a proposed challenge on effort sense, heart rate (HR), ventilation ([dotVE), and ventilatory equivalent VE/VO2), a measure of ventilatory efficiency. METHODS: Highly trained endurance athletes (VO2max = 68.46 +/- 1.47 mL x kg(-1) x min(-1) ran two sessions at approximately 75% of VO2max for 35 min in a control condition and a proposed challenge condition. During the control condition, the subjects ran on a treadmill while simultaneously viewing a video depicting a runner exercising at 75% of VO2max and were told the run would continue at a speed that elicited 75% of VO2max. During the proposed challenge condition, subjects completed the same exercise protocol but viewed a video of a struggling runner and were told that the treadmill speed would be increased to "an extremely difficult" 95% of VO2max matching the intensity of the runner on the video. However, after data assessment at 17 min, subjects were told that the treadmill was malfunctioning and the treadmill speed could not be altered. The same intensity was maintained in both conditions. RPE, HR, VE, and VE/VO2 were assessed during the treadmill runs at 10, 17, 25, and 35 min. RESULTS: The effects of the manipulation were represented by a significant increase in state anxiety immediately following the video proposing the 95% challenge. RPE, HR, and VE increased similarly under both conditions, while VE/VO2 did not change. CONCLUSION: These findings suggest that for highly trained endurance athletes, anticipation of proposed challenge during running does not influence cardiorespiratory responses; thus these athletes demonstrate a "physiologically toughened" response.     

Children's OMNI Scale of Perceived Exertion: walking/running evaluation

PURPOSE: The Children's OMNI-walk/run Scale of Perceived Exertion (category range, 0-10) was evaluated using male and female children (6-13 yr of age) during a treadmill graded exercise test. METHODS: A cross-sectional, perceptual estimation paradigm using a walking/running test protocol was administered. Oxygen uptake (VO(2), mL x min(-1)), %VO(2max), ventilation (VE, L x min(-1)), respiratory rate (RR, breaths x min(-1)), respiratory exchange ratio (RER), heart rate (HR, beats x min(-1)), V(E)/VO(2) ratio, and ratings of perceived exertion (RPE) measurements were made every minute throughout the test. RESULTS: Significant correlations were found between OMNI-walk/run Scale RPE responses and VO(2), %VO(2max), HR, V(E)/VO(2) ratio, and RR throughout the maximal treadmill exercise test. The strongest correlations were found between RPE and %VO(2max) (r = 0.41-0.60, P < 0.001) and HR (r = 0.26-0.52, P < 0.01). CONCLUSION: The psychophysiological responses provide validity evidence for use of the Children's OMNI-walk/run Scale over a wide range of exercise intensities during both walking and running.     

Load carriage energy expenditure with and without hiking poles during inclined walking

The purpose of this study was to compare load carriage energy expenditure with and without using hiking poles. Twenty male volunteers aged 20-48yr (Mean=29.8yr) completed two randomly ordered submaximal treadmill trials with poles (E) and without poles (C). Poles and load (15 kg backpack) were fitted for each subject according to the manufacturers' suggestions. Heart rates (HR), minute ventilation (V(E)), oxygen consumption (O2), caloric expenditure (Kcal), and rating of perceived exertion (RPE) were recorded at the end of each minute. Two trials separated by one week consisted of a constant treadmill speed of 1.5 mph and 1 min at 10% grade, 2 min at 15% grade, 2 min at 20% grade, and 10 min. at 25% grade. Mean HR (E = 144.8 +/- 24.4 b x min(-1); C = 144.0 +/- 25.7 b x min(-1)) and mean V(E) (E=51.4 +/- 15.8L x min(-1); C=50.8 +/- 17.0L x min(-1)), VO2 (E = 26.9 +/- 6.1 ml x kg(-1) x min(-1); C = 27.4 +/- 6.6 ml x kg(-1) x min(-1)), and Kcal (E = 10.6 +/- 2.9 Kcal x min(-1); C = 10.8 +/- 3.1 Kcal x min(-1)) were not significantly different between the two conditions. RPE (E = 13.28 +/- 1.2; C = 14.56 +/- 1.2) was significantly lower (P < 0.05) with hiking poles. Analysis of paired time points yielded no significant differences in HR, VO2, V(E), and Kcal, however, RPE means were significantly lower for 5 of the last 7 trial minutes with the use of poles. These results suggest that during load carriage on moderate grade, the weight and use of hiking poles does not increase energy expenditure but may provide reduced perceptions of physical exertion.     

Effect of cadence on the economy of uphill cycling.

Competitive cyclists generally climb hills at a low cadence despite the recognized advantage in level cycling of high cadences. To test whether a high cadence is more economical than a low cadence during uphill cycling, nine experienced cyclists performed steady-state bicycling exercise on a treadmill under three randomized trials. Subjects bicycled at 11.3 km.h-1 up a 10% grade while 1) pedalling at 84 rpm in a sitting position-84 Sit, 2) pedalling at 41 rpm in a standing position-41 Stand, and 3) pedalling at 41 rpm in a sitting position-41 Sit. Heart rate (HR), oxygen consumption (VO2), ventilation (VE), and respiratory exchange ratio were measured continuously during 5-min trials and averaged over the last 2 min. Additionally, rating of perceived exertion was recorded during the fifth minute of each trial, and blood lactate concentration was recorded immediately before and after each trial. Significantly lower values for HR, VO2 and VE were recorded during 84 Sit (164 +/- 3 bpm, 51.8 +/- 0.8 ml.min-1 x kg-1, 94 +/- 5 l.min-1) than for either the 41 Stand (171 +/- 2 bpm, 53.1 +/- 0.7 ml.min-1 x kg-1, 105 +/- 6 l.min-1) o 41 Sit (168 +/- 2 bpm, 53.1 +/- 0.8 ml.min-1 x kg-1, 101 +/- 6 l.min-1) trials. No other differences were noted between trials for any of the measured variables. We conclude that uphill cycling is more economical at a high versus a low cadence.     

The VO2max of recreational athletes before and after pregnancy.

This study was designed to test the hypothesis that pregnancy has an added training effect (increases "absolute" VO2max) in well-conditioned, recreational athletes. VO2max was measured serially in 20 nonpregnant recreational athletes who maintained their exercise within +/- 10% of initial levels over a 15-month period and 20 similar women who conceived and continued exercise at a reduced level during pregnancy with a return to within 20% of initial levels by 12 wk postpartum. Initially the two groups were similar in terms of age (30 +/- 1 vs 30 +/- 2 yr), weight 57.6 +/- 7.2 vs 59.7 +/- 7.5 kg), max pulse rate (189 +/- 8 vs 187 +/- 10 bpm), and absolute (3083 +/- 469 vs 3138 +/- 464 ml.min-1) VO2max. In the nonpregnant group the values obtained 15 months later were unchanged (weight = 57.8 +/- 6.6 kg, max pulse = 191 +/- 7 bpm, VO2max = 2977 +/- 397 ml.min-1) while those who conceived had a significant increase in absolute VO2max that was evident 12-20 wk postpartum and was maintained at the time of final testing 36-44 wk postpartum (3368 +/- 435 ml.min-1). Both weight (60.1 +/- 8.1 kg) and maximum pulse rate (185 +/- 12 bpm) were unchanged. These data indicate that pregnancy is followed by a small but significant increase in VO2max in recreational athletes who maintain a moderate to high level of exercise performance during and after pregnancy.     

Comparison of incremental treadmill exercise and free range running

PURPOSE: The aim of this study was to compare physiological responses during incremental treadmill exercise and free range running. METHODS: Fifteen competitive cross-country runners performed an incremental treadmill test and an unpaced 1-mile run on an indoor 200-m track. Physiological variables (VO(2peak), HR(peak), VO(2) x HR(-1)(peak), V(Epeak)) were measured using a portable metabolic analyzer. Blood lactate was measured post exercise. Outcome variables were analyzed with repeated measures ANOVA. RESULTS: Although directionally similar to previous studies with cycle ergometry, the observed peak values (track vs treadmill) for VO(2) (63.0 +/- 7.4 vs 61.9 +/- 7.2 mL x kg(-1) x min(-1)), V(E) (147 +/- 37 vs 144 +/- 30 L x min(-1)), HR (188 +/- 5 vs 189 +/- 7 beats.min-1), and VO(2) x HR(-1) (22.1 +/- 4.4 vs 21.5 +/- 4.5) were not significantly different. The observed peak values for blood lactate (14.4 +/- 3.3 vs 11.7 +/- 3.0 mmol x L(-1)) were significantly (P < 0.05) different. CONCLUSIONS: The results are not in full agreement with previous findings from cycling studies with the exception of post exercise blood lactate. Whether this represents a fundamental lack of effect of free range exercise or is related to mode specificity remains to be determined.     

Running performance in middle-school runners

AIM: This study examined the relationship of 3-km run time to indices of aerobic and anaerobic ability in 9 male runners (13.4+/-0.6 years, mean+/-SD). METHODS: Anthropometric measurements were made, and an exercise test to determine running economy at 187 m x min(-1) and (.-)VO(2max) were assessed on a treadmill. On a separate day, 2 55-m sprints followed by a 3-km run were performed on a 200-m indoor track. Capillary blood samples were obtained from a finger tip immediately after the run to determine blood lactate level. Fractional utilization (%(.-)VO(2max) used during the 3-km run) was calculated. Correlations were used to examine the relationship between run time and the physiological measurements. RESULTS: Mean values for (.-)VO(2), HR and RER at maximal exercise were 61.7+/-4.4 ml x kg(-1)xmin(-1), 198.9+/-6.7 b x min(-1), and 1.16+/-0.04, respectively. The average time to run 3 km was 13.27+/-0.97 min (90.1+/-7.2% of (.-)VO(2max)). Post-run blood lactate level was 8.3+/-3.2 mmol x L(-1) and was significantly related (r=-0.73, p=0.02) to 3-km time. Fractional utilization tended to be related (r=-0.56, p=0.12) to time. CONCLUSIONS: In this age group the ability to run at a high percentage of (.-)VO(2max) and tolerate a high blood lactate appear to be important determinants of running performance in young male runners.     

Oxygen uptake and heart rate responses during hypoxic exercise in children and adults

Control of ventilation and heart rate during exercise appears to undergo maturation, while aerobic metabolism (VO2) may not. Since we had previously found that hypoxia during exercise produced different ventilatory responses in children (C) compared to adults (A), we hypothesized that VO2 and heart rate kinetics during exercise would show similar maturational responses to hypoxia. To test this hypothesis, we examined the responses during progressive (ramp) and constant work rate tests in children and adults breathing either room air or hypoxic gas (FiO2 = 0.15). When corrected for body weight, children and adults had similar values for lactic acidosis threshold (LAT) (C: 29.1 +/- 5.0 ml.min-1.kg-1; A: 27.9 +/- 4.3) and VO2max (C: 40.7 +/- 8.6 ml.min-1.kg-1; A: 45.2 +/- 6.7) during normoxia. Hypoxia significantly lowered LAT (C: 27.5 +/- 5.4 ml.min-1.kg-1; A: 23.2 +/- 3.8; both P less than 0.05) and VO2max (C: 37.7 +/- 8.3 ml.min-1.kg-1; A: 40.1 +/- 5.3; both P less than 0.05) in both children and adults. Metabolic efficiency (delta VO2/delta work rate) and the VO2-heart rate relationship (delta VO2/delta HR/kg) were similar in the two groups and unaffected by hypoxia. During the constant work rate exercise, VO2 kinetics (time constant during phase 2 of the response (pi 1) and the O2 deficit) were similar between children and adults and were significantly slowed by hypoxia, consistent with current understanding of the control of oxidative metabolism. Finally, heart rate was increased at rest and during exercise with hypoxia, while the time to reach 75% of the end-exercise response was delayed significantly, in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Physiological and perceptual responses to cycle and treadmill exercise during pregnancy

We compared physiological and perceptual responses to non-weight bearing (cycle) and weight bearing (treadmill) exercise in 16 sedentary women throughout a normal term pregnancy. Subjects were recruited late in the first trimester (less than 13 wk gestation) and were studied at 4 wk intervals throughout pregnancy and 4 wk postpartum (PP). Exercise consisted of four 5 min protocols; two were performed on the cycle (C1 = 50 W; C2 = 75 W) and two on the treadmill (T1 = 66 m.min-1, 2.5% grade; T2 = 66 m.min-1, 12% grade). Measured variables included oxygen consumption (VO2), heart rate (HR), minute ventilation (VE), and ratings of perceived exertion (RPE, 10-point Borg scale). Absolute VO2 (ml.min-1) during cycle exercise increased (P less than 0.001) by 25 wk gestation, while relative VO2 (ml.kg-1.min-1) during treadmill walking was unchanged through late pregnancy and PP. This suggests that cycle exercise is not a true non-weight bearing exercise within a given group of women throughout gestation. Subjects' VO2max values were estimated at each test interval and found to increase (P less than 0.001) by 25-28 wk gestation. Heart rate and RPE responses to exercise remained constant throughout gestation and decreased (P less than 0.01) PP. Although they did not participate in a regular exercise program, it appears that our subjects experienced a mild aerobic training effect during late pregnancy.     

Rating of perceived exertion during high-intensity treadmill running.

PURPOSE: The purpose of this investigation was 1) to evaluate the time course of the rating of perceived exertion (RPE; 6-20 Borg scale) during short-term, high-intensity, constant-load running (ST); and 2) to determine the reproducibility of RPE during ST. METHODS: Fifteen well-trained males (VO2max = 58.0 +/- 4.6 mL x kg(-1) x min(-1), mean +/- SD) performed treadmill running (i.e., between 3 and 4 m.s-1 at 10.5% incline) to volitional exhaustion (Tlim) at an exercise intensity equivalent to 125% VO2max. A total of four RPE measurements were taken during each test, one every 30 s during the first 120 s of the exercise. The tests were repeated at the same time of day on three occasions within a 3-wk period. RESULTS: Tlim for the three tests was 197.6 +/- 34.8 s. RPE was linearly related with exercise time (mean +/- SD for the three tests: RPE at 30 s = 10.8 +/- 2.2; RPE at 60 s = 12.6 +/- 1.8; RPE at 90 s = 14.5 +/- 1.7; RPE at 120 s = 16.0 +/- 1.9; RPE = 9.06 + (0.06 x time (s)); r = 0.71, SEE = 2.0, P < 0.01). Repeated ANOVA revealed no systematic bias between the three tests for RPE, and other measures of reliability were also favorable. These included intraclass correlation coefficients ranging from 0.78 to 0.87 and sample coefficients of variation of between 4.4% and 6.0%. The 95% limits of agreement ranged between 0.0 +/- 2.3 and 0.0 +/- 2.5. CONCLUSION: ST RPE displays a positive linear response during the first 2 min. The measurement of ST RPE appears to be reliable and could thus add a new dimension to ST investigations.     

Physiological, anthropometric, and training correlates of running economy.

Potential physiological, anthropometric, and training determinants of running economy (RE) were studied in a heterogeneous group of habitual distance runners (N = 188, 119 males, 69 females). RE was measured as VO2 (ml.kg-1.min-1) during level treadmill running at 161 m.min-1 (6 mph) (VO2-6). Examined as potential determinants of RE were heart rate and ventilation while running at 6 mph (HR6, VE6), VO2max (ml.kg-1 x min-1), % fat, age, gender, height, weight, estimated leg mass, typical training pace, training volume, and sit-and-reach test performance. RE was entered as the dependent variable and the potential determinants as independent variables in zero-order correlation and multiple regression analyses. Zero-order correlation analysis found VO2max, HR6, and VE6 to be significantly, positively correlated with VO2-6 (P < 0.001). Multiple regression analysis, in which the independent effect of each predictor variable was examined, revealed VO2-6 to be positively correlated with VO2max (P < 0.001), HR6 (P < 0.001), VE6 (P < 0.001), and age (P < 0.05) and negatively correlated with weight (P < 0.01). These findings indicate that, in a diverse group of runners, better RE (VO2-6) is associated with lower VO2max, lower submaximal exercise VE and HR, lower age, and greater weight.     

The influence of acute hypoxia on the prediction of maximal oxygen uptake using multi-stage shuttle run test

BACKGROUND: The purpose of this study was to investigate changes in predicted maximal oxygen uptake (VO(2max)) by the multistage shuttle run test (MSSR) and several physiological parameters in MSSR under normoxia and two hypoxic conditions and the influences of acute hypoxia on these changes in MSSR. METHODS: Experimental design: six college long distance runners (LR), seven college rugby athletes (RG) and eight untrained college males (UM) performed incremental running test on the treadmill and MSSR in 17.5% (HYP(17.5%)) and 15.5% (HYP(15.5%)) of oxygen concentration and normoxia (NOR(20.9%)). Measures: VO(2max) was measured by the treadmill protocol and predicted by MSSR. Maximal heart rate (HR(max)) and maximal blood lactate concentration (BLa(max)) were recorded at the termination of each test. RESULTS: Significant correlation was observed between measured VO2(max) by the treadmill protocol (57.2+/-8.3 ml x kg(-1) x min(-1)) and predicted VO(2max) in NOR(20.9%) (54.6+/-8.0 ml x kg(-1) x min(-1)) (r=0.80, p<0.05). Also strong correlations in predicted VO(2max) between NOR(20.9%) and HYP(17.5%) (51.1+/-8.0 ml x kg(-1) x min(-1)) (r=0.90, p<0.05) and between NOR(20.9%) and HYP(15.5%) (48.1+/-7.3 ml x kg(-1) x min(-1)) (r=0.82, p<0.05) were observed. CONCLUSIONS: The results show that although MSSR underpredicts VO(2max), it is effective to evaluate aerobic power and can detect the influence of oxygen concentration on aerobic power. The specific movement of MSSR may affect the performance of LR but MSSR can describe the influence of hypoxia on the performance of LR compared to normoxia. Thus MSSR can be used to evaluate the influence of hypoxia or altitude on aerobic power as a field test.     

Metabolic and perceptual responses during Spinning cycle exercise

PURPOSE: The present investigation was undertaken to compare metabolic and perceptual responses between exercise performed at constant intensity (CON) and with a Spinning protocol of variable intensity (VAR). METHOD: Fifteen subjects, including seven males and eight females (23 +/- 5 yr, 72 +/- 17 kg, and 171 +/- 10 cm), underwent two experimental trials. During each trial, subjects performed a 30-min cycle exercise protocol that was followed by a 30-min recovery period. Exercise was performed at 67 +/- 3% (means +/- SD) of HR(max) in CON. In VAR, the similar intensity (68 +/- 4% HR(max)) was also achieved, although the protocol entailed alternating phases of both higher and lower intensity arranged similarly to what is designed for a typical Spinning workout. Oxygen uptake (VO2) and HR were measured at rest and throughout both exercise and recovery, whereas RPE were recorded during exercise only. Plasma lactate concentrations [La] were determined at rest, the end of exercise, and the end of recovery. RESULTS: No differences in average VO2, HR, and RPE were found during exercise between CON and VAR. However, average VO2 and HR were higher (P < 0.05) in VAR than CON (0.33 +/- 0.03 vs 0.26 +/- 0.02 L x min(-1) and 91 +/- 3 vs 80 +/- 2 beats x min(-1), respectively). [La] was higher (P < 0.05) at the end of exercise in VAR than CON (7.2 +/- 0.8 vs 2.7 +/- 0.3 mmol x L(-1)), but became similar at the end of recovery. CONCLUSION: An exercise regimen in which intensity varies exerts no added effect on metabolic and perceptual responses during exercise as long as the average intensity is kept the same. However, VAR resulted in a greater [latin capital V with dot above]O2 after exercise, and this augmented postexercise oxygen consumption may be mediated in part by elevated plasma [La].     

Acute reduction in maximal oxygen uptake after long-distance running

Nine male marathon runners, 24 to 39 years of age, were studied during steady state and maximal graded treadmill exercise under control conditions (C) and immediately after a paced outdoor 21.1-km run averaging 89.5 min (E). The half-marathon run and both treadmill trials were performed at 239 +/- 33 m/min. Oxygen uptake (VO2), respiratory exchange ratio (RER), heart rate (HR), plasma lactate concentration (PLa), and rating of perceived exertion (RPE) were measured in the steady state at 0% grade and at the fatigue end point. Compared to C, mean values in E were significantly lower (p less than 0.05) for time to exhaustion (6.0 vs 4.1 min), VO2max (60.0 vs 56.3 ml/kg/min), peak RER (1.18 vs 1.06), and PLa (9.7 vs 7.8 mM/L), whereas maximal HR (184 vs 184 b/min) and peak RPE (19.6 vs 19.9) were not significantly different between trials. Submaximal VO2 during steady-state runs was similar between C and E (44.4 vs 45.0 ml/kg/min; p = NS). Since the attainable VO2max decreased after E, the percentage of VO2max utilized during steady-state runs was higher, averaging 74% in C and 80% in E (p less than 0.05). In the steady state during E, HR (153 vs 161 b/min) and RPE (13.2 vs 14.8) were higher (p less than 0.05), and the increase in PLa from rest (2.7 vs 1.9 mM/L) was lower (p less than 0.05). Submaximal HR during graded exercise in E was 7 to 8 b/min higher (p less than 0.05) at a given VO2, indicating reduced heart rate reserve.(ABSTRACT TRUNCATED AT 250 WORDS)