Greater rate of decline in maximal aerobic capacity with age in endurance-trained than in sedentary men.

To determine the relation between habitual endurance exercise status and the age-associated decline in maximal aerobic capacity [i.e., maximal O(2) consumption (Vo(2 max))] in men, we performed a well-controlled cross-sectional laboratory study on 153 healthy men aged 20-75 yr: 64 sedentary and 89 endurance trained. Vo(2 max) (ml. kg(-1). min(-1)), measured by maximal treadmill exercise, was inversely related to age in the endurance-trained (r = -0.80) and sedentary (r = -0.74) men but was higher in the endurance-trained men at any age. The rate of decline in Vo(2 max) with age (ml. kg(-1). min(-1)) was greater (P < 0.001) in the endurance-trained than in the sedentary men. Whereas the relative rate of decline in Vo(2 max) (percent decrease per decade from baseline levels in young adulthood) was similar in the two groups, the absolute rate of decline in Vo(2 max) was -5.4 and -3.9 ml. kg(-1). min(-). decade(-1) in the endurance-trained and sedentary men, respectively. Vo(2 max) declined linearly across the age range in the sedentary men but was maintained in the endurance-trained men until approximately 50 yr of age. The accelerated decline in Vo(2 max) after 50 yr of age in the endurance-trained men was related to a decline in training volume (r = 0.46, P < 0.0001) and was associated with an increase in 10-km running time (r = -0.84, P < 0.0001). We conclude that the rate of decline in maximal aerobic capacity during middle and older age is greater in endurance-trained men than in their sedentary peers and is associated with a marked decline in O(2) pulse.     

Changes in maximal aerobic capacity with age in endurance-trained women: 7-yr follow-up.

On the basis of cross-sectional data, we previously reported that the absolute, but not the relative (%), rate of decline in maximal oxygen consumption (VO(2 max)) with age is greater in endurance-trained compared with healthy sedentary women. We tested this hypothesis by using a longitudinal approach. Eight sedentary (63 +/- 2 yr at follow-up) and 16 endurance-trained (57 +/- 2) women were reevaluated after a mean follow-up period of 7 yr. At baseline, VO(2 max) was ~70% higher in endurance-trained women (48.1 +/- 1.7 vs. 28.1 +/- 0.8 ml. kg(-1). min(-1). yr(-1)). At follow-up, body mass, fat-free mass, maximal respiratory exchange ratio, and maximal rating of perceived exertion were not different from baseline in either group. The absolute rate of decline in VO(2 max) was twice as great (P < 0.01) in the endurance-trained (-0.84 +/- 0.15 ml. kg(-1). min(-1). yr(-1)) vs. sedentary (-0.40 +/- 0.12 ml. kg(-1). min(-1). yr(-1)) group, but the relative rates of decline were not different (-1.8 +/- 0.3 vs. -1.5 +/- 0.4% per year). Differences in rates of decline in VO(2 max) were not related to changes in body mass or maximal heart rate. However, among endurance-trained women, the relative rate of decline in VO(2 max) was positively related to reductions in training volume (r = 0.63). Consistent with this, the age-related reduction in VO(2 max) in a subgroup of endurance-trained women who maintained or increased training volume was not different from that of sedentary women. These longitudinal data indicate that the greater decrease in maximal aerobic capacity with advancing age observed in middle-aged and older endurance-trained women in general compared with their sedentary peers is due to declines in habitual exercise in some endurance-trained women. Endurance-trained women who maintain or increase training volume demonstrated age-associated declines in maximal aerobic capacity not different from healthy sedentary women.     

Age and aerobic power: the rate of change in men and women

The historic studies by Robinson and Astrand as well as more recent studies present a fairly uniform rate of decline in VO2max with age at 0.40-0.50 ml X kg-1 X min-1 X year-1 in men. In women the rate of decline appears to be less--approximately 0.20-0.35 ml X kg-1 X min-1 X year-1, at least in cross-sectional studies. Further, there is no clear distinction in the rate of change in VO2max when comparing active and inactive populations. Longitudinal studies varying from 2.5 to 21 to 56 years present a confounding picture. The rate of decline in VO2max varies from 0.04 to 1.43 ml X kg-1 X min-1 X year-1. There is some indication that active individuals decline at a slower rate than inactive persons but the results are not uniform. A possible explanation is that changes in VO2max over the entire age range may be curvilinear, with active individuals declining slowly as long as they maintain a regular exercise program, and sedentary individuals declining at a rapid rate during their 20's and 30's followed by a slower rate of decline of their VO2max as they age further.     

Maximal aerobic capacity across age in healthy Hispanic and Caucasian women.

We tested the hypothesis that the age-related decline in maximal aerobic capacity, as measured by maximal oxygen uptake (VO(2 max)), is greater in Hispanic than in Caucasian women. We studied 146 healthy sedentary women aged 20-75 yr: 53 Hispanic (primarily of Mexican descent) and 93 Caucasian (non-Hispanic white). The groups did not differ in mean age, body mass, percent body fat, estimated physical activity-related energy expenditure, or education-based socioeconomic status (SES). During maximal exercise, respiratory exchange ratio, rating of perceived exertion, and percent predicted maximal heart rate were similar across age and ethnicity, suggesting equivalent maximum voluntary efforts in all subjects. VO(2 max) (ml x kg(-1) x min(-1)) was inversely related to age (P < 0.01) in Caucasian (r =-0.68) and Hispanic (r = -0.61) women. The absolute rate of decline in VO(2 max) with age was the same in the two groups (-0.31 ml x kg(-1) x min(-1) x yr(-1)). The relative rate of decline (% from age 25 yr) also was similar in the Caucasian (-9.0%) and Hispanic (-9.2%) women. When subjects of all ages were pooled, mean levels of VO(2 max) were similar in the two groups (approximately 28 ml x kg(-1) x min(-1)). These results, the first to our knowledge in Hispanics, indicate that mean levels of VO(2 max), as well as the rate of decline in VO(2 max) with age, are similar in healthy sedentary Hispanic and Caucasian women of similar SES. Thus it does not appear that Hispanic ethnicity per se modulates maximal aerobic capacity in this population.     

Sweat lactate secretion during exercise in relation to women's aerobic capacity

The purpose of this investigation was to determine whether sweat lactate secretion during exercise [approximately 70% maximum O2 consumption (VO2max), 60 min] differed in active vs. sedentary female subjects. Sweat rate, total sweat lactate secretion, and sweat lactate concentration were monitored in a group of sedentary (VO2max = 41.0 +/- 1.62 ml X kg-1 X min-1) and active (VO2max = 51.2 +/- 3.20 ml X kg-1 X min-1) women. Sweat rate was significantly (P less than 0.05) greater in the active subjects. There was a significant difference between groups in total amount of sweat lactate secreted (P less than 0.05), with the active group secreting less lactate (29.8 +/- 5.03 mmol, mean +/- SE) than the sedentary group (50.2 +/- 6.61 mmol). Concomitant with the lower total sweat lactate secretion in the active subjects was a significantly (P less than 0.05) more dilute sweat lactate concentration (42.6 +/- 14.08 vs. 100.4 +/- 32.37 mM). In these female subjects, sweat lactate concentration was inversely correlated (r = -0.79, P less than 0.01, n = 10) to sweat rate. It is concluded that total sweat lactate loss is significantly less in active than in sedentary women and that the active subjects secrete a greater quantity of lactate dilute sweat.     

Decline in VO2max with aging in master athletes and sedentary men

Fifteen well-trained master endurance athletes [62.0 +/- 2.3 (SE) yr] and 14 sedentary control subjects (61.4 +/- 1.4 yr) were reevaluated after an average follow-up period of approximately 8 yr to obtain information regarding the effects of physical activity on the age-related decline in maximal O2 uptake capacity (VO2max). The master athletes had been training for 10.2 +/- 2.9 yr before initial testing and continued to train during the follow-up period. The sedentary subjects' VO2max declined by an average of 3.3 ml.kg-1.min-1 (33.9 +/- 1.7 vs. 30.6 +/- 1.6, P less than 0.001) over the course of the study, a decline of 12% per decade. In these subjects maximal heart rate declined 8 beats/min (171 vs. 163) and maximal O2 pulse decreased from 0.20 to 0.18 ml.kg-1.beat (P less than 0.05). The master athletes' VO2 max decreased by an average of 2.2 ml.kg-1.min-1 (54.0 +/- 1.7 vs. 51.8 +/- 1.8, P less than 0.05), a 5.5% decline per decade. The master athletes' maximal heart rate was unchanged (171 +/- 3 beats/min) and their maximal O2 pulse decreased from 0.32 to 0.30 ml.kg-1.beat (P less than 0.05). These findings provide evidence that the age-related decrease in VO2max of master athletes who continue to engage in regular vigorous endurance exercise training is approximately one-half the rate of decline seen in age-matched sedentary subjects. Furthermore our results suggest that endurance exercise training may reduce the rate of decline in maximal heart rate that typically occurs as an individual ages.     

Enhanced endothelium-dependent vasodilation in older endurance-trained men.

We hypothesized that abnormal endothelium-dependent vasodilation (EDD) found in older otherwise healthy subjects can be attenuated with long-term endurance training. Ten endurance-trained men, 68.5 +/- 2.3 yr old, and 10 healthy sedentary men, 64.7 +/- 1.4 yr old, were studied. Aerobic exercise capacity (VO(2 max)), fasting plasma cholesterol, insulin, and homocysteine concentrations were measured. Master athletes had higher VO(2 max) (42 +/- 2.3 vs. 27 +/- 1.4 ml. kg(-1). min(-1), P < 0.001), slightly higher total cholesterol (226 +/- 8 vs. 199 +/- 8 mg/dl, P = 0.05), similar insulin, and higher homocysteine (10.7 +/- 1.3 vs. 9.2 +/- 1.4 micromol/ml, p = 0.02) concentrations. Brachial arterial diameter, determined with vascular ultrasound, during the hyperemic response was greater in the master athletes than in controls (P = 0.005). Peak vasodilatory response was 109.1 +/- 2 vs. 103.6 +/- 2% (P < 0.05) in the athletes and controls, respectively. Endothelium-independent vasodilation in response to nitroglycerin was similar between the two groups. The increased arterial diameter during the hyperemic response correlated significantly with the VO(2 max) in the entire population (r = 0.66, P < 0.002). Our results suggest that long-term endurance exercise training in older men is associated with systemic enhanced EDD, which is even detectable in the conduit arteries of untrained muscle.     

Smaller age-associated reductions in leg venous compliance in endurance exercise-trained men

We determined the independent and interactive influences of aging and habitual endurance exercise on calf venous compliance in humans. We tested the hypotheses that calf venous compliance is 1) reduced with age in sedentary and endurance-trained men, and 2) elevated in young and older endurance-trained compared with age-matched sedentary men. We studied 8 young (28 +/- 1 yr) and 8 older (65 +/- 1) sedentary, and 8 young (27 +/- 1) and 8 older (63 +/- 2) endurance-trained men. Calf venous compliance was measured in supine subjects by inflating a venous collecting cuff, placed above the knee, to 60 mmHg for 8 min and then decreasing cuff pressure at 1 mmHg/s to 0 mmHg. Calf venous compliance was determined using the first derivative of the pressure-volume relation during cuff pressure reduction (compliance = beta(1) + 2. beta(2). cuff pressure). Calf venous compliance was reduced with age in sedentary (approximately 40%) and endurance-trained men (approximately 20%) (both P < 0.01). Furthermore, calf venous compliance was approximately 70-120% greater in endurance-trained compared with age-matched sedentary men and approximately 30% greater in older endurance-trained compared with young sedentary men (both P < 0.01). These data indicate that calf venous compliance is reduced with age in sedentary and endurance-trained men, but compliance is better preserved in endurance-trained men.     

Endothelial function in highly endurance-trained men: effects of acute exercise

Exercise training reverses endothelial dysfunction, but the effect in young, healthy subjects is less clear. We determined the influence of maximal oxygen uptake (VO2max) and a single bout of high-intensity exercise on flow-mediated dilatation (FMD), brachial artery diameter, peak blood flow, nitric oxide (NO) bioavailability, and antioxidant status in highly endurance-trained men and their sedentary counterparts. Ten men athletes (mean +/- SEM age 23.5 +/- 0.9 years, height 182.6 +/- 2.4 cm, weight 72.5 +/- 2.4 kg, VO2max 75.9 +/- 0.8 mL.kg.min) and seven healthy controls (age 25.4 +/- 1.2 years, height 183.9 +/- 3.74 cm, weight 92.8 +/- 3.9 kg, VO2max 47.7 +/- 1.7 mL.kg.min) took part in the study. FMD, brachial artery diameter, and peak blood flow were measured using echo-Doppler before, 1 hour, 24 hours, and 48 hours after a single bout of interval running for 5 x 5 minutes at 90% of maximal heart rate. NO bioavailability and antioxidant status in blood were measured at all time points. Maximal arterial diameter and peak flow were 10-15% (P < 0.02) and 28-35% (P < 0.02) larger, respectively, in athletes vs. controls at all time points, and similar FMD were observed, apart from a transient decay of FMD in athletes 1 hour post exercise. NO bioavailability increased significantly after exercise in both groups and decreased to baseline levels after 24 hours in controls but remained increased 80% and 93% above baseline 24 and 48 hours post exercise in athletes. Antioxidant status was equal in the two groups at baseline and increased by approximately 10% 1 hour post exercise, an effect that lasted for 24 hours. Athletes had larger arterial diameter but similar FMD as untrained subjects, i.e., athletes had larger capacity for blood transport compared with their untrained counterparts. The observed FMD, bioavailability of NO, and antioxidant status in blood were highly dependent on the time elapsed after the exercise session.     

Role of muscle loss in the age-associated reduction in VO2 max

A progressive decline in maximal O2 consumption (VO2max) expressed traditionally as per kilogram body weight generally occurs with advancing age. To investigate the extent to which this decline could be attributable to the age-associated loss of metabolically active tissue, i.e., muscle, we measured 24-h urinary creatinine excretion, an index of muscle mass, in 184 healthy nonobese volunteers, ages 22-87 yr, from the Baltimore Longitudinal Study of Aging who had achieved a true VO2max during graded treadmill exercise. A positive correlation was found between VO2max and creatinine excretion in both men (r = 0.64, P less than 0.001) and women (r = 0.47, P less than 0.001). As anticipated, VO2max showed a strong negative linear relationship with age in both men and women. Creatinine excretion also declined with age in men and women. When VO2max was normalized for creatinine excretion, the variance in the VO2max decline attributable to age declined from 60 to 14% in men and from 50 to 8% in women. Thus comparing the standard age regression of VO2max per kilogram body weight with that in which VO2max is normalized per milligram creatinine excretion, the decline in VO2max between a hypothetical 30 yr old and a 70 yr old was reduced from 39 to 18% in men and from 30 to 14% in women. We conclude that in both sexes, a large portion of the age-associated decline in VO2max in non-endurance-trained individuals is explicable by the loss of muscle mass, which is observed with advancing age.     

Enhanced endothelial vasoreactivity in endurance-trained older men.

Using external vascular ultrasound, we measured brachial artery diameter (Diam) at rest, after release of 4 min of limb ischemia, i. e., endothelium-dependent dilation (EDD), and after sublingual nitroglycerin, i.e., non-endothelium-dependent dilation (NonEDD), in 35 healthy men aged 61-83 yr: 12 endurance athletes (A) and 23 controls (C). As anticipated, treadmill exercise maximal oxygen consumption (VO(2 max)) was significantly higher in A than in C (40. 2 +/- 6.6 vs. 27.9 +/- 3.8 ml. kg(-1). min(-1); respectively, P < 0. 0001). With regard to arterial physiology, A had greater EDD (8.9 +/- 4.2 vs. 5.7 +/- 3.5%; P = 0.02) and a tendency for higher NonEDD (13.9 +/- 6.7 vs. 9.7 +/- 4.2%; P = 0.07) compared with C. By multiple linear regression analysis in the combined sample of older men, only baseline Diam (beta = -2.0, where beta is the regression coefficient; P = 0.005) and VO(2 max) (beta = 0.23; P = 0.003) were independent predictors of EDD; similarly, only Diam (beta = -4.0; P = 0.003) and VO(2 max) (beta = 0.27; P = 0.01) predicted NonEDD. Thus endurance-trained older men demonstrate both augmented EDD and NonEDD, consistent with a generalized enhanced vasodilator responsiveness, compared with their sedentary age peers.     

A hemodynamic comparison of young and older endurance athletes during exercise

This study assessed the hemodynamic responses to exercise of master athletes (56 +/- 5 yr of age) who placed in the top 10% of their age groups in local 10-km competitive events, competitive young runners (26 +/- 3 yr), young runners matched in training and performance to the master athletes (25 +/- 3 yr), and healthy older sedentary subjects (58 +/- 5 yr). The maximal O2 consumption (VO2max) of the master athletes was 9 and 19% lower than that of the matched young and competitive young runners, respectively. When compared at the same relative submaximal work rates, these three groups had similar stroke volumes and arteriovenous O2 (aVO2) differences, though the master athletes had lower VO2, cardiac output, and heart rate, and higher vascular resistance. The older sedentary group had a lower stroke volume, aVO2 difference, and higher vascular resistance than the master athletes. Maximal stroke volume and estimated aVO2 difference were the same in the three groups of athletes; the lower maximal heart rate of the master athletes appears to account for their lower VO2max. The older sedentary subjects' VO2max was 47% lower than that of the master athletes; this difference was almost equally the result of a lower stroke volume and a lower a-VO2 difference. Thus these older athletes did not exhibit the decline in maximum stroke volume and aVO2 difference that occurs with aging in sedentary individuals; they also appear to have retained a greater peripheral vasodilatory response than their sedentary peers.     

Relationships between skeletal muscle characteristics and aerobic performance in sedentary and active subjects

Forty-eight sedentary and 39 quite active or well-trained men participated in this study. Muscle biopsy samples were taken from the vastus lateralis for the determination of fiber type composition (I, IIa, IIb), fiber type area, and assay of the following enzymes: malate dehydrogenase (MDH), 3-hydroxyacyl CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH). Maximal oxygen uptake (VO2max) was determined with a progressive cycle ergometer test, while endurance performance or maximal aerobic capacity (MAC) was defined as the total work output during a 90-min cycle ergometer test. Correlation analysis revealed no evidence of association between fiber type composition and VO2max kg-1 or MAC kg-1 in sedentary subjects, while active men exhibited significant correlation between % type I (r = 0.52), % type IIb (r = 0.31) and VO2max kg-1. Enzyme activities were not significantly correlated with MAC kg-1 and VO2max kg-1 in sedentary men while active men exhibited significant correlation for the three enzymes (0.37 less than or equal to r less than or equal to 0.51) with VO2max kg-1. These results show that the contribution of muscle fiber type and enzyme activities to aerobic performance may be inflated from a statistical point of view by the training status heterogeneity of subjects. They also suggest that variation in these muscle characteristics does not account for the individual differences in aerobic performance of subjects who have never trained before. Therefore, the assessment of muscle characteristics is not as useful as originally thought for the detection of individuals with a high potential for endurance performance among untrained subjects.     

Influence of ageing on aerobic parameters determined from a ramp test

The purpose of this study was to examine the four parameters of aerobic function, the maximum oxygen uptake (VO2max), ventilation threshold (ThVE), efficiency, and the effective time constant for oxygen consumption (tau'VO2), across age. In particular, the study was designed to observe whether there may be accelerated declines in aerobic function beyond 60 years of age. Seventy-nine sedentary men aged 30-84 years were studied. Each subject performed two maximal cycle ramp function tests, and data were collected on a breath-by-breath basis. The VO2max, from a plateau in VO2, was achieved in 87% of the subjects using the ramp test. The VO2max showed a significant decrease with increasing age (from linear regression, r = -0.81) at a rate averaging 0.037 l.min-1.year-1. The ThVE also declined with increasing age, but at a slower rate (0.013 l.min-1.year-1). The tau'VO2 was significantly increased across the age groups from 69 s for those aged 30-40 years to 98 s for those aged 60 years or more. There was no evidence of accelerated decline in these aerobic parameters beyond age 60 years, and there were no differences in efficiency (27.5-29.9%) across age. Although other forcing functions should be used to confirm this characterization of the oxygen kinetics, this slowed response with age would result in greater oxygen deficit and possibly earlier fatigue in response to even light exercise in older individuals.     

Rate of decline in blood lactate after cycling exercise in endurance-trained and -untrained subjects

The purpose of this study was to compare the rate of decline in blood lactate (La) levels in nine trained men [maximal O2 consumption (VO2max) 65.5 +/- 3.3 ml.kg-1.min-1] and eight untrained men (VO2max 42.2 +/- 2.8 ml.kg-1.min-1) during passive recovery from a 3-min exercise bout. Trained and untrained subjects cycled at 85 and 80% VO2max, respectively, to produce similar peak blood La concentrations. Twenty samples of arterialized venous blood were drawn from a heated hand vein during 60 min of recovery and analyzed in an automated La analyzer. The data were then fitted to a biexponential function, which closely described the observed data (r = 0.97-0.98). There was no difference in the coefficient expressing the rate of decline in blood La for trained and untrained groups (0.0587 +/- 0.0111 vs. 0.0579 +/- 0.0100, respectively). However, trained subjects demonstrated a faster time-to-peak La (P = 0.01), indicative of a faster efflux of La from muscle to blood. Thus the rate of decline in blood La after exercise does not appear to be affected by training. The faster decline previously reported for trained subjects may be due to the use of a linear rather than a biexponential curve fit.     

Decline in insulin action with age in endurance-trained humans.

We tested the hypothesis that regular endurance exercise prevents the age-related decline in insulin action typically observed in healthy, sedentary adults. An index of whole body insulin sensitivity (ISI), obtained from minimal model analysis of insulin and glucose concentrations during a frequently sampled intravenous glucose tolerance test, was determined in 126 healthy adults: 25 young [27 +/- 1 (SE) yr; 13 men/12 women] and 43 older (59 +/- 1 yr; 20/13) sedentary and 25 young (29 +/- 1 yr; 12/13) and 33 older (60 +/- 1 yr; 20/13) endurance trained. ISI values were lower in the older vs. young adults in both sedentary (-53%; 3.9 +/- 0.3 vs. 7.0 +/- 0.7 x10(-4) x min(-1) x microU(-1) x ml(-1); P < 0.01) and endurance-trained (-36%; 7.9 +/- 0.6 vs. 12.4 +/- 1.0 x 10(-4) min(-1) x microU(-1) x ml(-1); P < 0.01) groups, but the value was 72-102% higher in the trained subjects at either age (P < 0.01). In subgroup analysis of sedentary and endurance-trained adults with similar body fat levels (n = 62), the age-related reduction in ISI persisted only in the endurance-trained subjects (12.9 +/- 1.9 vs. 8.7 +/- 1.2 x 10(-4) x min(-1) x microU(-1) x ml(-1); P < 0.01). The results of the present study suggest that habitual endurance exercise does not prevent the age-associated decline insulin action. Moreover, the age-related reduction in ISI in endurance-trained adults appears to be independent of adiposity.     

Ageing and isokinetic plantar flexion

Isokinetic torques (Cybex II) of the plantar flexors in 25 healthy men were compared at 5 angular velocities (30, 60, 90, 120 and 180 degrees X s-1). The purposes were to compare plantar flexion torques in young and old subjects, and to determine whether the expected decrease was significantly associated with age, physical activity, or aerobic fitness. Four groups were studied: young (21.7 +/- 2.0 years) and older (63.3 +/- 2.8 years), active and sedentary. Measurements of height, weight, % body fat, VO2max, and daily leisure energy expenditure (questionnaire) were determined for each subject. Statistical measures of analysis of variance were used to determine significant differences among groups; product moment correlation and stepwise regression analysis were used to describe the degree of association between the dependent variable of plantar flexion torque and the independent variables at each velocity. A decline in torque was observed as the isokinetic velocity of angular motion increased. Age alone was a significant determinant of plantar flexion torque, whereas at the slowest speed, when VO2max was used as an explanatory variable, age was not a significant determinant of torque. At 30 degrees X s-1 47% of the variance in torque was explained by VO2max while at 180 degrees X s-1 49% of the variance was explained by age.     

Age, sex, race, initial fitness, and response to training: the HERITAGE Family Study.

Effects of age, sex, race, and initial fitness on training responses of maximal O(2) uptake (VO(2 max)) are unclear. Data were available on 435 whites and 198 blacks (287 men and 346 women), aged 17-65 yr, before and after standardized cycle ergometer training. Individual responses varied widely, but VO(2 max) increased significantly for all groups. Responses by men and women and by blacks and whites of all ages varied widely. There was no sex difference for change (Delta) in VO(2 max) (ml. kg(-1). min(-1)); women had lower initial values and greater relative (%) increases. Blacks began with lower values but had similar responses. Older subjects had a lower Delta but a similar percent change. Baseline VO(2 max) correlated nonsignificantly with DeltaVO(2 max) but significantly with percent change. There were high, medium, and low responders in all age groups, both sexes, both races, and all levels of initial fitness. Age, sex, race, and initial fitness have little influence on VO(2 max) response to standardized training in a large heterogeneous sample of sedentary black and white men and women.     

Sweating and skin blood flow during exercise: effects of age and maximal oxygen uptake

Individuals greater than or equal to 60 yr of age are more susceptible to hyperthermia than younger people. However, the mechanisms involved remain unclear. To gain further insight, we examined the heat loss responses of 7 young (24-30 yr) and 13 older (58-74 yr) men during 20 min of cycle exercise [67.5% maximal O2 uptake (VO2max)] in a warm environment (30 degrees C, 55% relative humidity). Forearm blood flow (FBF) and chest sweat rate (SR) were plotted as a function of the weighted average of mean skin and esophageal temperatures [Tes(w)] during exercise. The sensitivity and threshold for each response were defined as the slope and Tes(w) at the onset of the response, respectively. When the young sedentary men were compared with a subgroup (n = 7) of the older physically active men with similar VO2max, the SR and FBF responses of the two groups did not differ significantly. However, when the young men were compared with a subgroup of older sedentary men with a similar maximal O2 pulse, the SR and FBF sensitivities were significantly reduced by 62 and 40%, respectively. These findings suggest that during a short exercise bout either 1) there is no primary effect of aging on heat loss responses but, rather, changes are associated with the age-related decrease in VO2max or 2) the decline in heat loss responses due to aging may be masked by repeated exercise training.     

Exercise effects on chromium excretion of trained and untrained men consuming a constant diet

Chromium excretion of eight trained and five sedentary men was determined on rest days and after exercise to exhaustion at 90% of maximum O2 consumption (VO2max) to determine if degree of physical fitness affects urinary Cr losses. Subjects were fed a constant daily diet containing approximately 9 micrograms Cr/1,000 kcal. VO2max of the trained runners was in the good or above range based on their age and that of the sedentary subjects was average or below. While consuming the control diet, basal urinary Cr excretion of subjects who exercise regularly was significantly lower than that of the sedentary control subjects, 0.09 +/- 0.01 and 0.21 +/- 0.03 microgram/day (mean +/- SE), respectively. When subjects consumed self-chosen diets, basal urinary Cr excretion of the trained subjects was also significantly lower than that of the untrained subjects. Daily urinary Cr excretion of trained subjects was significantly higher on the day of a single exercise bout at 90% VO2max compared with nonexercise days, 0.12 +/- 0.02 and 0.09 +/- 0.01 microgram/day, respectively. Urinary Cr excretion of sedentary subjects was not altered after controlled exercise. These data demonstrate that basal urinary Cr excretion and excretion in response to exercise are related to VO2max and therefore degree of physical fitness.