Response to muscular exercise following repeated simulated weightlessness

The effect of repeated weightlessness exposures on maximal aerobic capacity was determined when seven healthy men (36-48 yr) underwent two 10-d bedrest (BR) periods in the -6 degrees headdown position, which were separated by a 14-d recovery period. No prescribed exercise was performed by the subjects during the course of the experiment. A graded supine cycle ergometer test consisting of 4 min of unloaded pedaling at 60 rpm followed by increased work rate of 15 W X min-1 until volitional fatigue (max) was performed before (pre) and after (post) the first and second BR periods, i.e., BR1 and BR2, and again 14 d after BR2 (REC). During exercise, submaximal and maximal oxygen uptake (VO2), ventilation (VE), heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures were measured and the gas exchange anaerobic threshold (AT) was determined. Plasma volume (Vp, T-1824) and body composition were measured pre- and post-BR1 and BR2 and following REC. Compared to the respective pre-BR control values, VO2max decreased (p less than 0.05) by 8.7% after BR1 and 5.2% after BR2 but returned to pre-BR values following 14 d REC. Submaximal and maximal HR increased (p less than 0.05) post-BR1 and BR2 but returned to pre-BR levels after REC. The AT and Vp decreased (p less than 0.05) post-BR1 and BR2 but returned to pre-BR levels after REC. Body weight increased (p less than 0.05) gradually during the experiment and did not return to control values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gender differences in the progression of metabolic responses during incremental exercise

AIM: The present investigation was undertaken to elucidate the differences in the progression of metabolic responses during incremental exercise between men and women of similar maximal aerobic capacity. METHODS: Twenty males and 20 females served as subjects for the study. Each subject was randomly assigned to perform a graded exercise test on either a cycle ergometer or a treadmill. Of the 20 subjects within each gender, 10 were tested on the cycle ergometer, whereas the other half was tested on the treadmill. During each test, absolute VO2, relative VO2, and HR were recorded during the last 15 seconds of every minute throughout the test. These variables were then plotted separately as a function of work rate so that a best-fit linear regression equation was generated for each of the three plots. RESULTS: Under the cycle condition, we found no difference in slope of increment in absolute VO2 between genders. However, the slope of increment in relative VO2 and HR was greater (P<0.05) in women than men. A negative correlation (r=-0.858, P<0.05) was found between body mass and slope of increment in relative VO2 in men and women combined. Under the treadmill condition, the slope for absolute VO2 were greater (P<0.05) in men than women. However, in terms of relative VO2 and HR, no between-gender differences were observed in the slope of increment. A positive correlation (r=0.769, P<0.05) was found between body mass and slope of increment in absolute VO2 in men and women combined. CONCLUSIONS: These results indicate that the progression of metabolic responses during incremental exercise differs between men and women despite a similar fitness. These gender differences may be further attributed to body mass that seems to play a distinctive role when the incremental exercise is conducted on a cycle ergometer and treadmill.     

Heart rate recovery from submaximal exercise in boys and girls

PURPOSE: To examine the changes in heart rate (HR) after two different submaximal exercise bouts in boys and girls. METHODS: Eleven boys (10.5 +/- 1.0 yr) and 10 girls (10.8 +/- 0.7 yr) participated in this study. Each child completed an initial graded exercise test to determine peak VO2. On subsequent and separate days, a 5-min submaximal exercise bout on a cycle ergometer was performed. One bout was conducted at 70 W, and the other bout corresponded to an intensity of 85-90% of peak VO2. VO2 and HR were measured during and after (1 min and 3 min). HR recovery responses from each submaximal exercise bout were analyzed using a group by time ANOVA, and Pearson-product correlations were determined between resting HR, peak VO2, and postexercise HR responses. RESULTS: HR in the boys was lower at the end of exercise and the first minute of recovery versus girls but not at the 3rd min of recovery. There were no differences in HR recovery after the relative exercise bout. Resting HR was significantly correlated with postexercise HR from both bouts (r = 0.52-0.69), whereas peak VO2 did not correlate to postexercise HR. ANCOVA using resting HR as the covariate eliminated the gender different noted with the recovery from the 70-W bout. CONCLUSIONS: In summary, postexercise HR responses differed between boys and girls when submaximal exercise was performed at an absolute work rate. When exercise was performed at a relative intensity, HR recovery responses were similar between the two groups. Resting HR appears to account for variations in postexercise HR better than peak VO2.     

Aerobic capacity of older adults: a training study

The effects of a four month aerobic conditioning program on heart rate, blood pressure, maximal oxygen consumption (VO2max), and physical work capacity of 55-70 year old sedentary individuals were evaluated. Twenty-eight men and women participated in either 4 months of supervised fast walking or jogging at a prescribed target heart rate or stretching exercises for one hour, three days per week. Gains in VO2max (ml/kg/min) obtained during a Balke maximal treadmill test in aerobic and exercise control subjects were 27% and 9%, respectively. At posttesting subjects in both groups demonstrated improved maximal work rate, increased treadmill time, and experienced lower resting and recovery heart rates, lower resting systolic blood pressure, and fewer premature ventricular depolarizations during exercise testing. In 67 physician-supervised maximal exercise tests, only one subject did not achieve VO2max due to exercise induced arrhythmias. No events of morbidity or mortality occurred as a result of the exercise testing and training. Subjects were contacted 4 years after study participation to determine if they were adhering to an exercise program. Sixty-four percent reported exercising at least 3 days per week in large muscle activities. We conclude that four months of supervised aerobic and nonaerobic exercise training is sufficient to improve aerobic capacity and other indicators of fitness in older, sedentary men and women, and that these previously sedentary people are likely to continue exercising on an individual basis once they have experienced improved physical capacity.     

Oxygen uptake kinetics of constant-load work: upright vs. supine exercise

The purpose of this study was to compare oxygen uptake (VO2), O2 deficit, steady-state VO2, and recovery VO2 during the performance of a constant-load exercise in the supine and upright position. Ten male subjects (36-40 yr) performed one submaximal exercise test in the supine and one in the upright position consisting of 5 min rest, 5 min cycle ergometer exercise at 700 kg X min-1 and 10 min of recovery from exercise. The VO2 was measured continuously in all tests from 2-L aliquot air samples collected every 30 s. Steady-state VO2 was similar during supine and upright exercise. However, total VO2 during upright exercise was 0.30 L greater (p less than 0.05) than during supine exercise while O2 deficit and recovery VO2 in the upright position were 0.64 L and 0.22 L less (p less than 0.05) compared to the supine test. The larger O2 deficit during supine exercise resulted from a significantly greater VO2 halftime compared to that of the upright response. Despite the ability to eventually attain similar steady-state VO2, supine exercise results in a reduction of total VO2 capacity associated with an increase in the O2 deficit during submaximal constant-load exercise and manifested by elevated recovery VO2.     

Cardiovascular responses during upright and semi-recumbent cycle ergometry testing

To compare cardiovascular (CV) responses during cycle ergometry testing, 20 unmedicated mild hypertensive subjects (10 male, 10 female; mean age = 47.9 yr) underwent exercise testing on an upright (UP) cycle and a semi-recumbent (SR) cycle. Tests were administered in counterbalanced order on two separate days. Heart rate (HR), blood pressure (BP), ventilation (VE), and rate pressure product (RPP) were recorded at absolute workloads (1.0 and 1.5 l.min-1) as well as at relative workloads (50, 75, and 90% of VO2 peak). In addition, the CV variables were measured at rest and peak exercise for each position. At absolute submaximal levels, women had higher HR, VE, and RPP values in both positions, reflecting responses at a greater percentage of their maximum exercise capacity. At relative workloads, HRs were significantly lower at rest and at 75 and 90% VO2 peak in the SR position. Men had greater systolic blood pressure (SBP) and RPP in both positions, and RPP was significantly lower at rest and at 75 and 90% VO2 peak in the SR position. Women displayed lower VE at all relative workloads. At peak exercise, subjects achieved significantly higher peak heart rates on the upright cycle (UP = 163 bpm, SR = 157 bpm). The UP cycle was associated with higher levels of peak VO2. The ability to achieve a higher HR and greater VO2 at peak exercise suggests that the UP cycle ergometer may be a preferable mode to the SR ergometer for evaluating maximal exercise performance among patients with mild hypertension.     

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.     

Prescribing water-based exercise from treadmill and arm ergometry in cardiac patients.

This study investigated the appropriateness of prescribing upright water-based exercise from treadmill and arm ergometry in uncomplicated, trained patients with cardiovascular disease (CVD) who were accustomed to water-based activities. Ten male patients with established CVD (mean age 59.4 +/- 8.7 yr) underwent maximal treadmill and arm ergometry in randomized counterbalanced order (half of the patients completed the treadmill test first and the other half completed the arm ergometer test first). Electrocardiographic (ECG), rating of perceived exertion (RPE), and oxygen uptake (VO2) measurements were made during both tests. Patients performed upright water-based exercise at 60, 70, and 80% of their maximal treadmill heart rate for 6 min at each intensity in a heated pool with a water temperature of 28-30 degrees C. They also performed an easy tethered swim, defined as performing at a comfortable exercise intensity, eliciting a heart rate of 86% of the treadmill maximum. VO2 and RPE were collected for all water-based exercise. To compare the RPE and VO2 between water-based, treadmill, and arm ergometry exercise, individual regression equations were constructed between heart rate, VO2, and RPE for both treadmill and arm ergometry tests. VO2 and RPE were then compared at the same heart rates between the three exercise modes. At 60% intensity, treadmill exercise exhibited a higher VO2 than water-based and arm ergometry exercise (P less than 0.05) but similar RPE. At 70%, treadmill exercise still yielded higher VO2, but also lower RPE than (P less than 0.05) and arm ergometry exercise (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Rate and amplitude of adaptation to two intensities of exercise in men aged 65-75 yr

PURPOSE: To test the hypothesis that in males aged 65-75 yr when the total amount of work completed is similar in endurance training three times per week for 12 wk at either 50% or 70% peak oxygen uptake (VO2(peak)), there will be no significant difference in time course and amplitude of selected responses. METHODS: Subjects were randomly assigned to three groups: 70% VO2(peak), N = 19; 50% VO2(peak), N = 16; or control group, N = 19. Subjects underwent a maximal cycle exercise test and blood volume (Evans Blue) determination at 0, 4, 8, and 12 wk. A submaximal exercise test (50 W) was conducted at weeks 0 and 12 where cardiac output was determined. The exercise groups maintained the same exercise relative intensity throughout the 12 wk and completed a similar total amount of work. RESULTS: There were significant and similar increases in peak VO2, power and heart rate (HR) for both exercise groups. Linear models best described the time course for peak power and HR in both exercise groups. In the 70% VO2(peak) group, a quadratic model for VO2 and a linear model for VE were the best fit. There were no significant changes in blood or plasma volume for any groups over the 12 wk. Significant increases in stroke volume and significant decreases in HR at 50 W were found in both exercise groups after training. CONCLUSION: Moderate-intensity cycle exercise (50% VO2(peak)) to achieve 180-200 kJ per session, three times a week for 12 wk is a safe and effective stimulus for healthy asymptomatic men aged 65-75 yr to improve functional capacity in a primarily linear manner.     

Effects of a 7-day head-down tilt (-6 degrees) on the dynamics of oxygen uptake and heart rate adjustment in upright exercise

Oxygen uptake (VO2) kinetics and heart rate (HR) kinetics were studied in six healthy male students before and on days 1,3 and 5 after a continuous 7-d antiorthostatic bedrest (-6 degrees). The exercise test protocol consisted of pseudorandom binary sequences (PRBS) of workload (W) performed on a bicycle ergometer in the upright position (20 W - 80 W, 15 bits, 30 s per bit; the sequence was repeated three times). Amplitude ratio and phase of the W-VO2 and W-HR relations were computed at six harmonic frequencies in the range 0.014 - 0.084 rad X s-1. After bedrest the VO2 kinetics was found to be impaired at the harmonic frequencies greater than 0.056 rad X s-1. Additionally, the mean heart rate during the PRBS cycles was increased (108 +/- 15 as compared to 92 +/- 10 min-1). There were no significant effects on HR kinetics and on the static W-VO2 relation. During an endurance training program both VO2 and HR changes were restored to the pre-bedrest levels. It is concluded that the impairment of VO2 kinetics can be attributed mainly to muscular factors.     

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 responses associated with deer hunting

PURPOSE: Deer hunting is a popular recreational activity with a high rate of cardiovascular events. Previous studies have demonstrated large HR responses during deer hunting. This study compared the HR and metabolic costs of maximal treadmill (TM) exercise with those of hiking while deer hunting and while dragging a deer. METHODS: Healthy male volunteers (N = 16) performed a maximal TM exercise test, a 0.8-km hiking test, and a 0.4-km dragging test over lightly rolling terrain. VO2 was measured by portable spirometry and HR by radiotelemetry. RESULTS: HR averaged 74.0 +/- 7.0% and 89.1 +/- 4.5% of peak TM HR during the hike and drag, respectively. The peak HR observed during hiking and dragging was 83.2 +/- 6.0% and 94.9 +/- 4.2% of peak TM HR, respectively. VO2 averaged 62.2 +/- 15.8% and achieved a peak of 77.2 +/- 19.0% of TM VO2 while hiking. This corresponded to 86.8 +/- 17.3% and 108.1 +/- 22.3% of ventilatory threshold (VT), respectively. VO2 averaged 72.3 +/- 21.0% and achieved a peak of 91.2 +/- 21.4% of peak TM VO2 while dragging the deer. This corresponded to 101.5 +/- 27.7% and 128.5 +/- 26.8% of VT, respectively. The VO2/HR relationship showed significant (P < 0.05) difference between the dragging test and the TM test with a disproportionately high HR. The VO2/HR relationship between the hiking and TM tests was comparable. CONCLUSION: In part, the previously described large HR responses and high rate of cardiovascular complications associated with deer hunting may attributable to the elevated metabolic costs of associated activities.     

Short-arm (1.9 m) +2.2 Gz acceleration: isotonic exercise load-O2 uptake relationship

BACKGROUND: The deconditioning syndrome from prolonged bed rest (BR) or spaceflight includes decreases in maximal oxygen uptake (VO2max), muscular strength and endurance, and orthostatic tolerance. In addition to exercise training as a countermeasure, +Gz (head-to-foot) acceleration training on 1.8-2.0 m centrifuges can ameliorate the orthostatic and acceleration intolerances induced by BR and immersion deconditioning. PURPOSE: Study A was designed to determine the magnitude and linearity of the heart rate (HR) response to human-powered centrifuge (HPC) acceleration with supine exercise vs. passive (no exercise) acceleration. Study B was designed to test the hypothesis that moderate +Gz acceleration during exercise will not affect the respective normal linear relationships between exercise load and VO2max, HR, and pulmonary ventilation (VEBTPS). Study C: To determine if these physiological responses from the HPC runs (exercise + on-platform acceleration) will be similar to those from the exercise + off-platform acceleration responses. METHODS: In Study A, four men and two women (31-62 yr) were tested supine during exercise + acceleration and only passive acceleration at 100% [maximal acceleration (rpm) = Amax] and at 25%, 50%, and 75% of Amax. In Studies B and C, seven men (33+/-SD 7 yr) exercised supine on the HPC that has two opposing on-platform exercise stations. A VO2max test and submaximal exercise runs occurred under three conditions: (EX) exercise (on-platform cycle at 42%, 61%, 89% and 100% VO2max) with no acceleration; (HPC) exercise + acceleration via the chain drive at 25%,50%, and 100% Gzmax (35%, 72% and 100% VO2max); and (EXA) exercise (on-platform cycle at 42%, 61%, 89%, and 100% VO2max) with acceleration performed via the off-platform cycle operator at +2.2+/-0.2 Gz [50% of max (rpm) G]. RESULTS: Study A: Mean (+/-SE) Amax was 43.7+/-1.3 rpm (mean = +3.9+/-0.2, range = 3.3 to 4.9 Gz). Amax run time for exercise +acceleration was 50-70 s, and 40-70 s for passive acceleration. Regression of X HR on Gz levels indicated explained variances (r2) of 0.88 (exercise) and 0.96 (passive). The mean exercise HR of 107+/-4 (25%), to 189+/-13 (100%) bpm were 43-50 bpm higher (p < 0.05) than comparable passive HR of 64+/-2 to 142+/-22 bpm, respectively. Study B: There were no significant differences in VO2, HR or VEBTPS at the submaximal or maximal levels between the EX and EXA runs. Mean (+/-SE) VO2max for EX was 2.86+/-0.12 L x min(-1)(35+/-2 ml x min(-1) x kg(-1)) and for EXA was 3.09+/-0.14 L x min(-1) (37+/-2 ml-min(-1) x kg(-1)). Study C: There were no significant differences in the essentially linear relationships between the HPC and EXA data for VO2 (p = 0.45), HR (p < 0.08), VEBTPS (p = 0.28), or the RE (p = 0.15) when the exercise load was % VO2max. CONCLUSION: Addition of + 2.2 Gz acceleration does not significantly influence levels of oxygen uptake, heart rate, or pulmonary ventilation during submaximal or maximal cycle ergometer leg exercise on a short-arm centrifuge.     

Energy Cost of Simulated Rowing Using a Wind-Resistance Device

In brief: This study examined rowing as a form of aerobic exercise for people of average fitness. Ten male subjects performed maximal exercise tests on a treadmill and on a wind-resistance rowing device. VO₂ max was 10% lower in the rowing bout, but there were no significant differences in VE max and VE/O₂. A submaximal rowing test was also performed at five incremental work loads, and VO₂ increased curvilinearly with the velocity. The results suggest that rowing provides an adequate stimulus for aerobic training and that energy expenditure on the rowing ergometer can be estimated from the velocity readings.     

Cardiovascular responses during recreational 5-a-side indoor-soccer

The aims of this study were to examine the cardiovascular response to recreational 5-a-side indoor-soccer (5v5) matches (5v5 study, 5v5S, n=15) and to assess the validity of using heart rate (HR) to estimate oxygen uptake (VO(2)) demands during actual game-play (validity study, VS, n=16) in young subjects (age 16.8+/-1.5 years). Game responses during 5v5S were assessed during 30 min matches using short-range telemetry heart-rate monitors. In VS games (12 min), VO(2) and HR were monitored with a portable gas analyser (K4b(2), COSMED, Rome, Italy). Individual HR-VO(2) relationships were determined from a laboratory treadmill run to exhaustion (VS) and a multistage shuttle running fitness test (5v5S) using K4b(2). Results showed that 5v5 elicits 83.5+/-5.4 and 75.3+/-11.2% of HR(peak) and VO(2peak), respectively. Ninety-one percent of the playing time (30 min) was spent at HR higher than 70% of HR(peak). In VS match, gas analyses revealed that only 71% of HR variance was explained by VO(2) variations. However, playing at approximately 70% of HR(peak) elicited 51.6+/-11.2% of VO(2peak). Group actual versus predicted VO(2) values demonstrated no significant differences (p>0.05), however, large confidence limits were observed (+6.20 and -10.53 mlkg(-1)min(-1)). These results show that HR and VO(2) responses to recreational 5v5 soccer in young athletes are similar to the exercise intensities recommended by ACSM for promoting cardiovascular health and suggest that HR is valid to prescribe and monitor aerobic intermittent exercise. These results also show that HR measures are acceptable for estimating VO(2) during intermittent exercise when assessing large groups, but show that large estimation errors can occur at the individual level.     

The effects of exercise on children with attention-deficit hyperactivity disorder

PURPOSE: The effects of exercise on children with attention-deficit hyperactivity disorder (ADHD) were evaluated by studying the rate of spontaneous eye blinks, the acoustic startle eye blink response (ASER), and motor impersistence among 8- to 12-yr-old children (10 boys and 8 girls) meeting DSM-III-R criteria for ADHD. METHODS: Children ceased methylphenidate medication 24 h before and during each of three daily conditions separated by 24-48 h. After a maximal treadmill walking test to determine cardiorespiratory fitness (VO(2peak)), each child was randomly assigned to counterbalanced conditions of treadmill walking at an intensity of 65-75% VO(2peak) or quiet rest. Responses were compared with a group of control participants (11 boys and 14 girls) equated with the ADHD group on several key variables. RESULTS: Boys with ADHD had increased spontaneous blink rate, decreased ASER latency, and decreased motor impersistence after maximal exercise. Girls with ADHD had increased ASER amplitude and decreased ASER latency after submaximal exercise. CONCLUSIONS: The findings suggest an interaction between sex and exercise intensity that is not explained by physical fitness, activity history, or selected personality attributes. The clinical meaning of the eye blink results is not clear, as improvements in motor impersistence occurred only for boys after maximal exercise. Nonetheless, these preliminary findings are sufficiently positive to encourage additional study to determine whether a session of vigorous exercise has efficacy as a dopaminergic adjuvant in the management of behavioral features of ADHD.     

Bedrest-induced peak VO2 reduction associated with age, gender, and aerobic capacity

To compare the factors of age and gender on aerobic work capacity following bedrest-induced deconditioning, peak oxygen uptake (peak VO2), heart rate (peak HR), and exercise tolerance time were measured in 15 middle-aged men (55 +/- 2 yr) and 17 middle-aged women (55 +/- 1 yr) before and after 10 d of continuous bedrest (BR). The average body weight following BR was unchanged in both men and women. Following BR, peak VO2 decreased from 35.6 +/- 2.0 to 32.6 +/- 1.1 ml . kg-1 . min-1 (-8.4%, p less than 0.05) in the men and from 26.5 +/- 1.4 to 24.7 +/- 1.3 ml . kg-1 . min-1 (-6.8%, p less than 0.05) in the women, while total exercise tolerance time was reduced by 8.1% (p less than 0.05) and 7.3% (p less than 0.05) in the men and women, respectively. The peak HR was elevated by BR from 158 +/- 4 to 165 +/- 4 bpm (+4.4%, p less than 0.05) in the men and from 157 +/- 4 to 159 +/- 4 bpm (+1.3%, NS) in the women. The percent changes in peak VO2, peak HR, and exercise tolerance time measured in the men were not significantly different compared to those of the women. The reduction in peak VO2 in the middle-aged men and women in the present study were comparable to the reductions of 9.3% and 7.8% observed in our earlier studies with 15 young men (21 +/- 1 yr) and 8 young women (28 +/- 2 yr), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Comparison of short-term aerobic training and high aerobic power on tolerance to uncompensable heat stress.

This study investigated whether, in subjects of moderate aerobic fitness, short-term aerobic training could replicate the improved physiological responses to exercise-heat stress observed in individuals with a high level of aerobic fitness. Males of moderate (MF; <50 ml x kg(-1) min(-1) VO2peak, n = 8) and high (HF; >55 ml x kg(-1) x min(-1) VO2peak, n = 8) aerobic fitness walked at 3.5 km x h(-1) in the heat (40 degrees C, 30% relative humidity) wearing nuclear, biological, and chemical protective clothing. Tests were conducted once on HF subjects and on MF subjects before (MF-Pre) and after (MF-Post) a 2-week program 6 d x week(-1) of daily aerobic training (1 h treadmill exercise at 65% VO2peak for 12 d, 22 degrees C, 40% relative humidity). The training significantly increased VO2peak by 6.5%, while heart rate (fc) and rectal temperature (Tre) rise decreased during exercise in a thermoneutral environment. HF had lower body mass and body fat content than MF, and VO2peak remained lower in MF pre-or post-training. In the heat, MF-Post had a decreased skin temperature (Tsk) and an increased sweat rate compared with MF-Pre, but no changes were observed in fc, Tre, or tolerance time (TT). No significant differences during the first 60 min in Tre and fc were observed between the MF-Post and the HF subjects, though the HF subjects exhibited a lower Tsk. The endpoint Tre, deltaTre, and TT remained significantly higher in HF than in either the MF-Pre or MF-Post subjects. It was concluded that, in preparation for exercise in an uncompensable heat stress environment, short-term aerobic training offers little, if any, benefit and is not an adequate substitute for a high level of aerobic fitness resulting from habitual exercise and training.