High-resistance versus variable-resistance training in older adults.

PURPOSE: The purpose of this study was to compare the effects of high-resistance (HR) training, 3 times.wk(-1) at 80% maximum strength (1RM) with 3 times.wk(-1) variable-resistance (VR) training (once-weekly training at 80%, 65%, and 50% 1RM) in older adults. METHODS: The study was a 6-month resistance training intervention conducted in the Birmingham Alabama metropolitan area, and included healthy volunteer men and women over the age of 60. Twenty-eight subjects were assigned randomly to two training groups. Eight volunteers served as controls. Before and after 25 wk of training, body composition was measured by densitometry; strength by isometric tests; and difficulty in performing daily activity tasks (DAT) by measuring heart rate, oxygen uptake, electromyography, and perceived exertion. In addition, 1RM strength was measured every 25 d throughout the 6 months of training. Repeated measures ANOVA and paired t-tests with Bonferroni corrections for additive alpha were used to analyze the data. RESULTS: The control group did not significantly change in any study parameter. No significant change in body weight occurred for any group. However, the HR and VR groups increased fat free mass (FFM) similarly (1.8 kg and 1.9 kg, respectively). Both training groups increased strength significantly, without significant differences in change. No significant change in oxygen uptake occurred during DAT. However, there was a significant time effect for heart rate and perceived exertion. Greater decrease in normalized integrated electromyography during the carry task was found in the VR group over the HR and control groups. CONCLUSION: Despite similar increases in strength and fat free mass, the VR group decreased difficulty of performing the carry task more than the HR group. These data suggest that larger improvements in DAT may be achieved if frequency of high-resistance training is less than 3 times.wk(-1).

The interrelationship among muscle mass, strength, and the ability to perform physical tasks of daily living in younger and older women.

The purpose of this study was to objectively compare the difficulty and determine the contribution of strength and muscle mass to the performance of physical tasks of daily living in a group of younger and older women. A cross-sectional design was used. Volunteer participants were from the community of Birmingham, AL; there were 21 older (aged 60-75 years) and 20 younger (23-34 years) healthy women in the study. Subjects were matched for height and weight. Their testing included total and regional body composition evaluation by use of dual-energy x-ray absorptiometry, isometric strength tests of elbow flexors and knee extensors, and integrated electromyography (IEMG) evaluation while the subjects were standing from and sitting into a chair, and while they were carrying a small load (weight relative to strength). A two-way analysis of variance and a two-way analysis of covariance with repeated measures, Pearson product correlation, and first-order partial correlations were used to analyze the data. A significant inverse correlation was observed between age and isometric strength of both the knee extensors and elbow flexors. Adjusting for upper leg lean tissue did not change the significant inverse correlation between age and knee extensor strength. However, after an adjustment for arm lean tissue, there was no significant correlation between elbow flexor strength and age. Older women experienced significantly greater difficulty in standing than younger women as measured by quadriceps normalized IEMG (i.e., IEMG during task/IEMG during maximum isometric strength test). This difference persisted even after the covariate upper leg lean tissue was added to the model. No significant difference was observed between younger and older women for difficulty (biceps normalized IEMG) during the carry task after the covariate arm lean tissue was added to the model. The older women in this study had less strength in the knee extensors and experienced greater difficulty standing from a chair than the younger women, even after the covariate upper leg lean tissue was added to the model. This suggests that other factors, in addition to loss of lean tissue, contribute to the age-related decline of muscular strength and the ability to perform tasks with the legs. In contrast, although elbow flexor strength declined, this appeared to be largely due to decreased arm lean tissue mass.

Resistance training increases total energy expenditure and free-living physical activity in older adults.

The purpose of this study was to determine what effects 26 wk of resistance training have on resting energy expenditure (REE), total free-living energy expenditure (TEE), activity-related energy expenditure (AEE), engagement in free-living physical activity as measured by the activity-related time equivalent (ARTE) index, and respiratory exchange ratio (RER) in 61- to 77-yr-old men (n = 8) and women (n = 7). Before and after training, body composition (four-compartment model), strength, REE, TEE (doubly labeled water), AEE (TEE - REE + thermic response to meals), and ARTE (AEE adjusted for energy cost of standard activities) were evaluated. Strength (36%) and fat-free mass (2 kg) significantly increased, but body weight did not change. REE increased 6.8%, whereas resting RER decreased from 0.86 to 0.83. TEE (12%) and ARTE (38%) increased significantly, and AEE (30%) approached significance (P = 0.06). The TEE increase remained significant even after adjustment for the energy expenditure of the resistance training. In response to resistance training, TEE increased and RER decreased. The increase in TEE occurred as a result of increases in both REE and physical activity. These results suggest that resistance training may have value in increasing energy expenditure and lipid oxidation rates in older adults, thereby improving their metabolic profiles.

Does acute exercise affect the susceptibility of low density lipoprotein to oxidation?

This study describes the effect of an acute exercise bout on the susceptibility of isolated low density lipoprotein (LDL) to in vitro oxidation. LDL was isolated from 23 subjects (exercisers, n = 11; sedentary, n = 12) immediately before and after a single bout of exercise (30 min of treadmill work at 55% & 70% peak oxygen consumption (VO2 peak) for exercisers and sedentary, respectively). A statistically significant decrease in lag time for LDL oxidation was observed following exercise compared to baseline (96.1+/-23.5 min vs. 92.1+/-23.3 minutes; n = 23, p < or = .03) using a 5 microM copper system. There was a statistically significant increase in plasma myeloperoxidase (MPO) levels following exercise compared to baseline values ( 1.58+/-.91 ng/dl versus 2.08+/-1.2 ng/dl; n = 12, p < or = .03). These results suggest that the 30 min exercise bout at a moderate intensity and duration was a sufficient oxidative stress to increase the susceptibility of LDL to in vitro oxidation. Additionally, the exercise bout appeared to activate neutrophils, subsequently releasing MPO protein.