Weight training improves walking endurance in healthy elderly persons.

OBJECTIVE: To determine the effect of a resistance-training program on walking endurance in a healthy, community-dwelling elderly population. DESIGN: 12- week randomized, controlled trial comparing a resistance- training group with a nonexercising control group. SETTING: Hospital-affiliated outpatient exercise facility. PATIENTS: 24 healthy men and women who were 65 years of age or older (mean age +/-SD, 70.4 +/- 4 years; range, 65 to 79 years). MEASUREMENTS: The primary outcome variable was exhaustive submaximal walking time measured at an intensity of 80% of baseline peak aerobic capacity. RESULTS: Participants in the resistance-training program increased submaximal walking endurance by 9 minutes (from 25 +/- 4 minutes to 34 +/- 9 minutes; P=0.001), a 38% increase, whereas no change was seen in controls (20 +/- 5 minutes to 19 +/- 10 minutes; P greater than 0.2; P=0.005 between groups). The relation between change in leg strength and change in walking endurance was significant (r=0.48; P=0.02). Neither group showed a change in peak aerobic capacity or in whole-body composition, although fat-free mass of the leg increased in the exercise group. CONCLUSIONS: Resistance training for 3 months improves both leg strength and walking endurance in healthy, community-dwelling elderly persons. This finding is relevant to older persons at risk for disability, because walking endurance and leg strength are important components of physical functioning.

Decrease in fat oxidation following a meal in weight-reduced individuals: a possible mechanism for weight recidivism.

This study examined the effect that dietary-induced weight loss has on body composition, energy metabolism, and substrate oxidation at rest and during the 5-hour period following a meal. Twenty older (age:mean +/- SE, 61 +/- 1 years; range, 56 to 70 y) obese (body mass index > 32 kg/m2) subjects (12 women, eight men) completed an 11-week dietary restriction program in which they lost 9 +/- l kg. Fat and fat-free mass were reduced (P < .05) by 15% and 5%, respectively. Resting metabolic rate decreased by 15% (P < .05). Overall, weight loss did not alter the percentage of energy derived from fat sources (approximately 47% of energy) under resting conditions. In contrast, the percentage of calories derived from fat during the 5-hour postmeal period decreased from baseline to post-weight loss from 38% +/- 3% to 26% +/- 4% (P < .05) of total calories expended. The reduction in fat oxidation subsequent to a meal may facilitate fat storage, and may be one mechanism by which one regains weight following weight loss.

Contrasting effects of resistance and aerobic training on body composition and metabolism after diet-induced weight loss.

This study examined whether exercise training facilitates maintenance of body weight at reduced levels following weight loss by attenuating weight loss-induced reductions in resting metabolism and fat oxidation. The effects of 12 weeks (three times per week) of either aerobic or weight training exercise on body weight, body composition, and energy metabolism during rest and following a meal in 18 older (mean +/- SE, 61 +/- 1 years; range, 56 to 70) subjects who had recently lost a mean of 9 +/- 1 kg were studied. During the exercise training period, the aerobic training group (five women, four men) had a significant (P < .05) reduction in body weight (-2.5 +/- 0.6 kg) as compared with the weight training group (five women, four men) (0.4 +/- 0.9 kg). Eight of nine aerobic training subjects lost additional weight, while six of nine weight training subjects gained weight. Neither type of training reversed the depressions in resting metabolism or fat oxidation rates (ie, resting or postprandial) that had occurred as a consequence of the prior weight loss. Thus, alterations in resting metabolism or fat oxidation (resting or postprandial) do not appear to be the mechanism(s) by which exercise training facilitates maintenance of diet-induced weight loss.

PFK activity in muscle and heart tissue is differentially affected by dietary restriction.

This research examined the effect of dietary restriction on PFK activity (one of the enzymes in the glycolytic pathway) in selected skeletal and heart muscle tissue. Fifty-five Sprague-Dawley female rats were separated into three different groups for 10 weeks of dietary restriction: AL = ad lib fed, MR = weight reduced to 81% of AL and SR = weight reduced to 63% of AL. Gastrocnemius white (GW), plantaris, soleus (S) and heart (H) muscle tissue were dissected out and assayed for PFK activity. PFK activity (mumole/g/min) in GW was 105 +/- 7, 86 +/- 6 and 61 +/- 6 for AL, MR & SR, respectively (AL > MR > SR, P < 0.05). PFK activity in S was 25 +/- 2, 22 +/- 1 and 16 +/- 1 for AL, MR and SR, respectively (AL, MR > SR, P < 0.05). In contrast, PFK activity in H was unaffected (P > 0.05). These data suggest that PFK activity in various muscle tissues is differentially affected during diet-induced weight loss.

A meta-analysis of the effects of exercise and/or dietary restriction on resting metabolic rate.

A meta-analysis was used to examine the independent and interactive effects of dietary restriction, endurance exercise training and gender on resting metabolic rate (RMR). Sixty different group means (covering approximately 650 subjects) were identified from the scientific literature and subjected to meta-analysis techniques. Collectively (i.e., all groups combined), body weight loss was greater (P < 0.05) for men (approximately 18 kg) than for women (approximately 12 kg). There were no statistically significant exercise training or gender effects on RMR during weight loss. Collectively (i.e., all groups combined), dietary restriction resulted in a -0.59 kJ.min-1 (approximately -12%) decrease in RMR (P < 0.05). When normalized to body weight, RMR was reduced by less than 2% (P < 0.05). These data suggest that exercise training does not differentially affect RMR during diet-induced weight loss. In addition, decreases in resting metabolism appear to be proportional to the loss of the metabolically active tissue.

Exercise-training enhances fat-free mass preservation during diet-induced weight loss: a meta-analytical finding.

A meta-analysis was performed to examine how exercise training and gender influence the composition of diet-induced weight loss. The groups did not differ with respect to either the amount of body weight lost (mean = -10 +/- 1.4 kg) or fat mass lost (mean = -8 +/- 1.1 kg). However, exercise training significantly (P < 0.05) reduced the amount of body weight lost as fat-free mass compared to dietary restriction only (DO) for the same sex. The percentage of weight lost as fat-free mass for diet-plus-exercise (DPE) subjects was approximately half (P < 0.05) of that for DO subjects of the same sex (DO males = 28 +/- 4% of weight lost as fat-free mass; DPE males = 13 +/- 6%, DO females = 24 +/- 2%, DPE females = 11 +/- 3%). These data provide evidence that exercise training reduces the amount of body weight lost as fat-free mass during diet-induced weight loss. In addition, sex differences do not seem to exist with respect to the composition of diet-induced weight loss.

Exercise intensity does not affect depression of resting metabolic rate during severe diet restriction in male Sprague-Dawley rats.

This study examined the effects of high and low intensity exercise on the resting metabolic rate during severe dietary restriction. We hypothesized that exercise would attenuate and/or offset the decline in resting metabolic rate during energy-deficit conditions. Thirty-two male 90-d-old Sprague-Dawley rats were divided into four groups: control, diet restriction only, diet restriction plus high intensity exercise, and diet restriction plus low intensity exercise. The body weights of the diet-restricted groups were rapidly reduced over 5 wk until rats in these three groups weighted 64% of control weight, and this difference in body weight was maintained for the last 5 wk of the study. The high and low intensity exercise groups ran 5 d/wk at 75 and 37.5%, respectively, of maximal running speed for 45 and 90 min/d, respectively. Resting metabolic rate (23-h oxygen uptake) was measured during wk 2, 4, 6, 8 and 10. Resting metabolic rate for the three diet-restricted groups was significantly lower (25-37%) than for the controls for all measurements. Exercise training had no effect on the diet-induced depression of resting metabolic rate, with the diet-restricted groups differing among each other by < 2% during the measurement periods. During severe diet-restriction, exercise-induced elevations of resting metabolic rate seem to be greatly reduced or eliminated. This absence of an exercise effect on resting metabolic rate persisted through 5 wk of reduced body weight maintenance. We conclude that during severe diet restriction, exercise offers no "protective" or enhancing effect on resting metabolic rate.

Changes in body composition and daily energy expenditure induced in rats during eight weeks of daily swim training.

The body weight, body composition, and daily (post-exercise) energy expenditure of five groups of male rats were examined following 1, 2, 4, 6 or 8 weeks of daily (1 h) swim training. Rats that swam daily weighed less than sedentary controls and had smaller adipose and lean tissue masses. The size of these body weight and composition changes grew as daily training progressed. Relative to sedentary rats, the 24 h (post-exercise) expenditure of swim-trained rats, expressed either per BW0.75kg or per g of body protein, was significantly higher after two weeks of daily training. This training-induced elevation in daily (post-exercise) expenditure likewise grew larger as training continued. After eight weeks, rats that swam, although now maintaining significantly smaller lean and adipose masses, expended more calories daily (post-exercise) than sedentary rats (42.2 vs. 39.2 kcal/day respectively). Thus, though exercise-induced elevations in expenditure have been associated with an increased lean tissue mass, other factors are apparently responsible for the progressive elevation (from sedentary levels) of 24 h expenditure found here with extended daily swim training.

Resting metabolic rate and coronary-heart-disease risk factors in aerobically and resistance-trained women.

This cross-sectional study compared physical characteristics, cardiovascular risk factors, and resting metabolic rate (RMR) in a cohort of 82 young women separated into three groups: sedentary (SED, n = 48), aerobically trained (AT, n = 21), and resistance trained (RT, n = 13). Body mass and fat-free mass (FFM) were not different between groups whereas percent body fat was lower in the AT (16.2 +/- 0.7%) and RT (14.7 +/- 0.8%) groups than in the SED group (21.8 +/- 0.8%). There were no between-group differences for blood pressure or blood lipids. RMRs (kJ/min) for the AT (4.31 +/- 0.06) and RT (4.25 +/- 0.09) groups were significantly greater than those for the SED group (3.99 +/- 0.05). When adjusted for differences in FFM, RMRs for the AT group (4.24 +/- 0.05) were different from those of both the RT (4.13 +/- 0.05) and SED (4.05 +/- 0.03) groups; RMRs for the RT and SED groups were not different from each other. No differences were found in cardiovascular risk in young nonobese women of differing exercise status. Aerobic training in young women seems to increase the rate of metabolic activity of resting tissues whereas resistance training does not.

Resting energy metabolism and cardiovascular disease risk in resistance-trained and aerobically trained males.

The objectives of this study were (1) to examine differences in resting metabolic rate (RMR) and cardiovascular risk factors among aerobically trained (n = 36), resistance-trained (n = 18), and untrained (n = 42) young males; and (2) to investigate the influence of body composition, dietary intake, and VO2max as possible modulators of differences in cardiovascular risk among groups. Results showed that RMR, adjusted for differences in fat-free weight (FFW), was 5% higher in aerobically trained males compared with resistance-trained males (P < .01), and 10% higher than that in untrained males (P < .01). Plasma levels of cholesterol and low-density lipoprotein cholesterol (LDL-C) were comparable between resistance-trained and aerobically trained males, but were lower (P < .05) than those in untrained males. (The percent intake of dietary fat was related to plasma cholesterol [r = .32, P < .01] and LDL-C [r = .30, P < .01].) When compared with untrained males, fasting triglyceride (TG) levels were 39% and 43% lower (P < .01) in resistance-trained and aerobically trained males, respectively. When compared with untrained males, the fasting insulin to glucose ratio (I/G) was 45% and 53% lower (P < .01) in resistance- and aerobically trained males, respectively. Mean arterial pressure (MAP) was 7% lower (P < .01) in aerobically trained compared with untrained males. Statistical control for differences in percent body fat or percent intake of dietary fat diminished the differences among the groups for plasma lipids, blood pressure, and the I/G ratio. We conclude that aerobically trained and resistance-trained males have higher resting energy requirements independent of FFW compared with untrained males. Aerobically trained and resistance-trained young males have comparable and favorable cardiovascular disease risk profiles compared with untrained males, and this appears to be related to their low level of adiposity and low intake of dietary fat.

Amount of exercise per day and weeks of training: effects on body weight and daily energy expenditure.

The effects of 16 wk of 1 or 3 h of daily swim-training on the body weight and 24-h postexercise energy expenditure of adult male Sprague-Dawley rats were examined. Daily energy expenditure (kcal.d-1.kg-0.75) of sedentary rats displayed the usual age-associated decline in daily energy expenditure (kcal.d-1.kg-0.75) over this 16-wk period. Daily swimming forestalled this decline, leading to differences in daily energy expenditure between exercised and sedentary rats, which grew progressively larger. One and 3 h of daily swimming led to similar declines in weight, but 3 h of daily swimming elevated daily (postexercise) expenditure after fewer weeks of training and to a greater extent than did 1 h of daily swimming. Exercise-induced elevations in daily (nonexercise) expenditure thus appear to be a joint function of how long the daily exercise program has been in effect and the amount of daily exercise.

Effect of exercise to rest ratio on plasma lactate concentration at work rates above and below maximum oxygen uptake.

The metabolic and physiological responses to different exercise to rest ratios (E:R) (2:1, 1:1, 1:2) of eight subjects exercising at work rates approximately 10% above and below maximum oxygen uptake (VO2max) were assessed. Each of the six protocols consisted of 15 1-min-long E:R intervals. Total work (kJ), oxygen uptake (VO2), heart rate (fc) and plasma lactate concentrations were monitored. With increases in either E:R or work rate, VO2 and fc increased (P < 0.05). The average (15 min) VO2 and fc ranged from 40 to 81%, and from 62 to 91% of maximum, respectively. Plasma lactate concentrations nearly doubled at each E:R when work rate was increased from 90 to 110% of VO2max and ranged from a low of 1.8 mmol.l-1 (1:2-90) to a high of 10.7 mmol.l-1 (2:1-110). The 2:1-110 protocol elicited plasma lactate concentrations which were approximately 15 times greater than that of rest. These data suggest that plasma lactate concentrations during intermittent exercise are very sensitive to both work rate and exercise duration.

A meta-analysis of the factors affecting exercise-induced changes in body mass, fat mass and fat-free mass in males and females.

A meta-analysis was performed to assess the effects of type, duration and frequency of exercise training on changes in body mass (BM), fat mass (FM), fat-free mass (FFM) and percent body fat (percent fat) both for adult males and females. Weight loss following aerobic type exercise training, though modest, was greater for males. Stepwise regression suggests that, both for males and females, energy expended during exercise and initial body fat levels (or body mass) account for most of the variance associated with changes in BM, FM and percent fat associated with aerobic-type exercise training. In females, weeks of training and duration of exercise per session were also significant predictors. These findings confirm earlier research in males concerning exercise training effects on body mass and body composition and extend them both to females and to a broader range of exercise types. Of particular interest in this regard is the finding that weight training exercise which is similar to aerobic exercise in facilitating body fat loss, can also preserve or increase fat-free mass.

Effect of dietary restriction and/or exercise on 23-h metabolic rate and body composition in female rats.

This study examined the effects of three levels of dietary intake [ad libitum fed (AL), moderately severe (MSR), and severe restriction (SR)] and two levels of exercise [cage confinement (CC) and exercise training (E)] on 23-h resting metabolic rate (RMR) and body composition in 47 female Sprague-Dawley rats. At the end of the 9-wk study, the MSR and SR groups weighed approximately 81 and 61%, respectively, of the AL-CC group. RMR was depressed for the MSR and SR groups compared with the AL-CC group. This was true whether expressed on an absolute (ml/min) or relative (ml.min-1.kg-0.75) basis. On a relative basis, which accounts for changes caused by weight loss alone, the RMR decreased by approximately 12 and 19%, respectively, for the MSR and SR groups compared with the AL-CC group. Although E resulted in significant differences in fat mass, percent fat, percent water, and heart mass between the AL groups, there were no significant differences between E and CC groups at either the MSR or SR level of dietary intake for any of the variables measured (i.e., body composition, muscle mass, RMR). Thus E does not appear to affect the composition of lost weight or RMR during diet-induced weight loss for female rats of normal weight.

Exercise training elevates RMR during moderate but not severe dietary restriction in obese male rats.

This study examined the effects of 11 wk of exercise training (E) on resting O2 uptake (RMR) and the composition of diet-induced weight loss in obese male Sprague-Dawley rats (n = 48). The rats underwent one of three levels of dietary treatment: ad libitum (AL), moderate restriction (MR), and severe restriction (SR). Compared with AL-CC (cage confined; 647 +/- 13 g), the AL-E (84% of AL-CC), MR-CC (77%), MR-E (77%), SR-CC (63%), and SR-E (63%) groups were all reduced in body mass. At the MR level, E significantly reduced fat mass (FM; MR-CC 73 +/- 5, MR-E 45 +/- 5 g) and increased water mass (WM; MR-CC 307 +/- 5, MR-E 329 +/- 5 g) compared with CC. In contrast, no significant differences existed between the SR-CC and SR-E groups. Exercise training did not result in conservation of protein mass at any level of dietary intake. Exercise training significantly elevated RMR (on a kg0.75 basis) by approximately 7% for the AL-E and MR-E groups compared with their respective dietary counterparts. These findings may help reconcile the conflicting results present in the literature with respect to the effects of exercise training during diet-induced weight loss. That is, studies using relatively severe dietary restrictions are less likely to demonstrate exercise-induced changes in RMR, FM, and WM than those employing moderate dietary restrictions.

Physiological responses during aerobic dance of individuals grouped by aerobic capacity and dance experience.

This study examined the effects of aerobic capacity (peak oxygen uptake) and aerobic dance experience on the physiological responses to an aerobic dance routine. The heart rate (HR) and VO2 responses to three levels (intensities) of aerobic dance were measured in 27 women. Experienced aerobic dancers (AD) (mean peak VO2 = 42 ml.kg-1.min-1) were compared to subjects with limited aerobic dance experience of high (HI) (peak VO2 greater than 35 ml.kg-1.min-1) and low (LO) (peak VO2 less than 35 ml.kg-1.min-1) aerobic capacities. The results indicated the LO group exercised at a higher percentage of peak heart rate and peak VO2 at all three dance levels than did either the HI or AD groups (HI = AD). Design of aerobic dance routines must consider the exercise tolerance of the intended audience. In mixed groups, individuals with low aerobic capacities should be shown how and encouraged to modify the activity to reduce the level of exertion.

Body composition, muscle and fat pad changes following two levels of dietary restriction and/or exercise training in male rats.

This study examined the effects of exercise training on conservation of lean mass during moderate and severe dietary restriction in male Sprague-Dawley rats. Eight rats each (48 total) were assigned to one of three levels of dietary restriction (ad lib., AL; moderate, MR; severe, SR) and to one of two activity levels (cage-confined, CC; or treadmill exercised, E) for a 10-week period. Post-intervention, the AL-E (91 percent), MR-CC (84 percent), MR-E (86 percent), SR-CC (66 percent) and SR-E (68 percent) groups all weighed less than the AL-CC group (427 +/- 4.3 g). Exercise training resulted in conservation of lean mass (protein + water + ash) at the moderate but not severe levels of dietary restriction. Further examination showed that this was mostly water since no between-group differences existed at any given diet level for protein or ash mass. Exercise training did elicit conservation of left ventricular heart muscle mass at both the moderate and severe levels of dietary restriction. In contrast, gastrocnemius muscle mass was conserved or maintained only at the moderate dietary restriction level. Thus, the level of dietary restriction appears to affect the ability of exercise training to elicit conservation of both total lean mass and the mass of individual muscles during diet-induced body mass reduction.

Exercise training attenuates diet-induced reduction in metabolic rate.

The combined influence of exercise training and dietary restriction on daily energy expenditure was evaluated by exposing 48 male Sprague-Dawley rats to one of three food intake conditions [ad libitum (AL), moderately restricted (MR), or severely restricted (SR)] and to one of two exercise conditions [treadmill exercised (E) or cage confined (CC)]. After 10 wk of exercise and dietary restriction, the MR-CC and MR-E rats weighed 84 and 86%, respectively, of AL-CC, whereas the SR-CC and SR-E rats weighed 66 and 68% of AL-CC. Dietary restriction and subsequent weight loss produced significant reductions in both total and resting daily energy expenditure. Exercise partially reversed this effect, but the extent of this reversal diminished as the severity of dietary restriction was increased. These results raise the distinct possibility that inconsistencies in the current literature concerning the effects of exercise on whole body metabolism during periods of dietary restriction might be reconciled by an appreciation and an understanding of the influence that duration of exercise training and severity of food restriction have on this measure.

Neither high- nor low-intensity exercise promotes whole-body conservation of protein during severe dietary restrictions.

The effects of 11 weeks of severe dietary restriction alone or in combination with either high- or low-intensity exercise on conservation of protein were studied in 32 male Sprague-Dawley rats. The rats were assigned to one of four groups: sedentary control (C), diet restriction alone (DO) or diet restriction in combination with either high-intensity (HI) or low-intensity (LO) exercise. The groups trained at either 75 percent (HI) or 37.5 percent (LO) of maximal running speed for up to 45 or 90 min/day, 5 days/week, respectively. Total (g) proteins, fat, water and ash content did not differ between the DO, HI and LO groups and were all reduced significantly in comparison to C. Similarly, heart, gastrocnemius muscle and epididymal fat pad masses were significantly reduced for the DO, HI and LO groups in comparison to C. However, the absolute decrease in heart mass was reduced for the HI group (heart mass = 0.31 percent of body mass) in comparison to the DO group (heart mass = 0.28 percent of body mass). Thus, in lean rats undergoing severe dietary restrictions, neither high- nor low-intensity exercise appears to affect total protein conservation in comparison to diet alone. However, high-intensity exercise training appears to attenuate cardiac but not skeletal muscle mass loss in the face of severe dietary restriction.