Biomedical subjects

D L Ballor

Publications and source records attributed to D L Ballor.

17 recordsLinked to original sources

PubMed1992

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.

Adult↗

PubMed1992

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.

Adolescent↗

PubMed1992

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.

Adipose Tissue↗

PubMed1992

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.

Animals↗

PubMed1991

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.

Adult↗

PubMed1991

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.

Animals↗

PubMed1991

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.

Animals↗

PubMed1991

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.

Adipose Tissue↗

PubMed1990

Exercise intensity does not affect the composition of diet- and exercise-induced body mass loss.

The effect of caloric restriction (1200 kcal/d intake) in combination with high (High) (80-90% of peak VO2) or low (Low) (40-50% of peak VO2) exercise work rates on the composition of lost body mass was determined in 27 obese women (percent fat, 36.7 +/- 4.2%; mean +/- SD). All subjects trained 3 d/wk for 8 wk, with the High (n = 14) and Low (n = 13) groups exercising for 25 and 50 min/d, respectively. After posttesting there were no differences between the groups with respect to pre- to posttest changes (mean of combined groups) in body mass (-7%), fat-free mass (-10%), fat mass (-16%), percent fat (-10%), and sum of five skinfold-thickness measurements (-16%). This study suggests that with regard to conservation of fat-free mass, the selection of an exercise intensity for a diet and exercise regimen may be left to the preference of the clinician and/or dieter.

Adult↗

PubMed1990

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.

Animals↗

PubMed1990

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.

Adipose Tissue↗

PubMed1990

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.

Animals↗

PubMed1989

Strength gains in obese females are unaffected by moderate dietary restriction.

This study examined the effects of dietary restriction on strength gains from whole body resistance training. Comparisons were made between diet-restricted (n = 12) and non-diet-restricted (n = 10) obese women (mean +/- SD, 36.7 +/- 7.0% fat) undergoing identical 8-week resistance training regimens. Diet-restricted subjects reduced their dietary intake by 4200 kJ/day and reduced body mass by 3.9 kg over 8 weeks. Ten-repetition maximum masses were compared between the groups on biweekly intervals. Results indicated no differences between the groups with respect to the rate or magnitude of strength gains for any of the eight exercises. Significant pre- to post-test increases in strength (p less than 0.05) were found for all eight exercises. The rate or magnitude of strength gains induced by resistance training does not appear to be affected by moderate dietary restrictions in obese females.

Adult↗

PubMed1989

Comparison of three methods of estimating energy expenditure: caltrac, heart rate, and video analysis.

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

Adolescent↗

PubMed1989

Physiological responses to nine different exercise:rest protocols.

This study determined the metabolic responses to different exercise:rest protocols during circuit exercise using hydraulic resistance. In experiment 1, nine subjects underwent nine different 27 min exercise circuits. There were three variations of three exercise:rest protocols (2:1, 1:1, 1:2). The VO2 for the nine circuits averaged (mean +/- SEM) 1.94 +/- 0.03 l.min-1 (43% of treadmill VO2max), with the largest difference between the protocols being 13%. Heart rate averaged 152.2 +/- 3.1 beats.min-1, with the largest difference between the protocols being 8%. Increasing the exercise duration per minute or the number of exercise bouts per minute had minimal effects on the mean VO2 and heart rate response to hydraulic resistive exercise. In experiment 2, nine subjects underwent three different 9 min exercise circuits using exercise:rest protocols of 2:1, 1:1, and 1:2 while work and VO2 were simultaneously measured. Surprisingly, increases in work were not necessarily accompanied by corresponding increases in VO2.

Adult↗

PubMed1988

Resistance weight training during caloric restriction enhances lean body weight maintenance.

To assess the individual and combined effects of weight loss and weight training on body weight and body composition, 40 obese women were randomly assigned to one of four groups for an 8 wk weight-loss study. These groups were control (C); diet without exercise (DO); diet plus weight training (DPE); and weight training without diet (EO). Body weight decreased for DO (-4.47 kg) and DPE (-3.89 kg) compared with C (-0.38 kg) and EO (0.45 kg). Lean body weight (LBW) increased for EO (1.07 kg) compared with DO (-0.91 kg) and C (-0.31 kg) and for DPE (0.43 kg) compared with DO. Upper-arm muscle areas (determined by radiograph) increased for DPE (11.2 cm2) and EO (10.4 cm2) compared with C (2.7 cm2) and DO (2.1 cm2). It was concluded that weight training results in comparable gains in muscle area and strength for DPE and EO. Adding weight training exercise to a caloric restriction program results in maintenance of LBW compared with DO.

Adult↗

PubMed1987

Metabolic responses during hydraulic resistance exercise.

Thirteen college-age men under-went a treadmill (TM)-graded VO2max exercise test on 1 d and a 24.5-min hydraulic resistive exercise circuit on a following day. Seven exercises were performed in the following order: leg extension, bent-over row, bicep curl, squat, upright row, bench press, and behind-neck press. Each exercise was performed three times with the following work-to-rest timing: 30 s exercise, 30 s rest; 30 s exercise; 30 s rest; and 30 s exercise, 60 s rest (to allow for machine switch-over to the next exercise). Thus, each exercise took a total of 120 s, of which work was for 90 s and rest 120 s. During the circuit, heart rate averaged 153.8 b X min-1 (81.2% of TM max) and VO2 averaged 1.93 l X min-1 (41.4% of TM max). Oxygen uptake for the individual exercises ranged from 1.52 l X min-1 (32.6% of TM max) for the behind-neck-press exercise to 2.43 l X min-1 (52.1% of TM max) for the squat exercise. Heart rate ranged from 135.9 b X min-1 (71.8% of TM max) for the leg extension exercise to 163.4 b X min-1 (86.3% of TM max) for the squat exercise. Hydraulic circuit resistance exercise results in an average caloric expenditure of 40.8 kJ X min-1 (9.75 kcal X min-1).

Adult↗