Ben F. Hurley

Strength training in the elderly: effects on risk factors for age-related diseases.

Strength training (ST) is considered a promising intervention for reversing the loss of muscle function and the deterioration of muscle structure that is associated with advanced age. This reversal is thought to result in improvements in functional abilities and health status in the elderly by increasing muscle mass, strength and power and by increasing bone mineral density (BMD). In the past couple of decades, many studies have examined the effects of ST on risk factors for age-related diseases or disabilities. Collectively, these studies indicate that ST in the elderly: (i) is an effective intervention against sarcopenia because it produces substantial increases in the strength, mass, power and quality of skeletal muscle; (ii) can increase endurance performance; (iii) normalises blood pressure in those with high normal values; (iv) reduces insulin resistance; (v) decreases both total and intra-abdominal fat; (vi) increases resting metabolic rate in older men; (vii) prevents the loss of BMD with age; (viii) reduces risk factors for falls; and (ix) may reduce pain and improve function in those with osteoarthritis in the knee region. However, contrary to popular belief, ST does not increase maximal oxygen uptake beyond normal variations, improve lipoprotein or lipid profiles, or improve flexibility in the elderly.

Age and gender responses to strength training and detraining.

PURPOSE The purpose of this study was to examine the effects of age and gender on the strength response to strength training (ST) and detraining. METHODS Eighteen young (20-30 yr) and 23 older (65-75 yr) men and women had their one-repetition maximum (1 RM) and isokinetic strength measured before and after 9 wk of unilateral knee extension ST (3 d x wk(-1)) and 31 wk of detraining. RESULTS The young subjects demonstrated a significantly greater (P < 0.05) increase in 1 RM strength (34+/-3%; 73+/-5 vs 97+/-6 kg; P < 0.01) than the older subjects (28+/-3%; 60+/-4 vs 76+/-5 kg, P < 0.01). There were no significant differences in strength gains between men and women in either age group with 9 wk of ST or in strength losses with 31 wk of detraining. Young men and women experienced an 8+/-2% decline in 1 RM strength after 31 wk of detraining (97+/-6 vs 89+/-6 kg, P < 0.05). This decline was significantly less than the 14+/-2% decline in the older men and women (76+/-5 vs 65+/-4 kg, P < 0.05). This strength loss occurred primarily between 12 and 31 wk of detraining with a 6+/-2% and 13+/-2% decrease in the young and older subjects, respectively, during this period. DISCUSSION These results demonstrate that changes in 1 RM strength in response to both ST and detraining are affected by age. However, ST-induced increases in muscular strength appear to be maintained equally well in young and older men and women during 12 wk of detraining and are maintained above baseline levels even after 31 wk of detraining in young men, young women, and older men.

Aerobic versus strength training for risk factor intervention in middle-aged men at high risk for coronary heart disease☆

To compare the effects of strength training (ST) to those of aerobic training (AT) for coronary heart disease (CHD) risk factor intervention, we studied 37 previously untrained males (aged 50 +/- 9 years, mean +/- SD) before and after 20 weeks of either ST (N = 14), AT (walk/jog, N = 13), or no exercise (inactive controls, N = 10). Lipoprotein and lipid profiles, blood pressure, and glucose and insulin responses to an oral glucose tolerance test (OGTT) were assessed before and after the training period in all three groups. The ST program produced significant reductions in plasma glucose levels at 60, 90, and 120 minutes (P < .05) after glucose ingestion, whereas the AT program resulted in significant reductions only at 90 and 120 minutes (P < .05). ST also decreased insulin levels during fasting (P < .05) and at 90 and 120 minutes (P < .01) after glucose ingestion. AT decreased insulin levels at 90 and 120 minutes (P < .01) after glucose ingestion. Both training programs reduced the total area under the glucose tolerance curve for glucose (both P < .05) and insulin (both P < .05), but there were no significant differences in these changes between the two groups. None of the glucose or insulin values were significantly altered in the control group. There were no significant changes in lipoprotein and lipid profiles or blood pressure in any of the three groups. These results suggest that ST and AT have comparable effects on risk factors for CHD.(ABSTRACT TRUNCATED AT 250 WORDS)

Resistive training can reduce coronary risk factors without altering VO2max or percent body fat.

Eleven healthy, untrained males (age = 44 +/- 1 yr; range = 40 to 55 yr) were studied to determine the effects of 16 wk of high-intensity resistive training on risk factors for coronary artery disease. Lipoprotein-lipid profiles, plasma glucose and insulin responses during an oral glucose tolerance test, and blood pressure at rest were determined before and after training. The training program resulted in a 13% increase in high-density lipoprotein-cholesterol (39 +/- 2 vs 44 +/- 3 mg.dl-1, P less than 0.05), a 43% increase in high-density lipoprotein-cholesterol (7 +/- 2 vs 10 +/- 2 mg.dl-1, P less than 0.05), a 5% reduction in low-density lipoprotein cholesterol (129 +/- 5 vs 122 +/- 5 mg.dl-1, P less than 0.05), and an 8% decrease in the total cholesterol/high-density lipoprotein-cholesterol ratio (5.1 +/- 0.3 vs 4.7 +/- 0.3, P less than 0.01), despite no changes in VO2max, body weight, or percent body fat. Glucose-stimulated plasma insulin concentrations during oral glucose tolerance testing were significantly lower, and supine diastolic blood pressure was reduced (P less than 0.05) as a result of the training program. No changes in any of these variables occurred in a sedentary control group. These findings indicate that resistive training can lower risk factors for coronary artery disease independent of changes in VO2max, body weight, or body composition.

Myostatin gene expression is reduced in humans with heavy-resistance strength training: a brief communication.

This study examined changes in myostatin gene expression in response to strength training (ST). Fifteen young and older men (n = 7) and women (n = 8) completed a 9-week heavy-resistance unilateral knee extension ST program. Muscle biopsies were obtained from the dominant vastus lateralis before and after ST. In addition to myostatin mRNA levels, muscle volume and strength were measured. Total RNA was reverse transcribed into cDNA, and myostatin mRNA was quantified using quantitative PCR by standard fluorescent chemistries and was normalized to 18S rRNA levels. A 37% decrease in myostatin expression was observed in response to ST in all subjects combined (2.70 ± 0.36 vs 1.69 ± 0.18 U, arbitrary units; P < 0.05). Though the decline in myostatin expression was similar regardless of age or gender, the small number of subjects in these subgroups suggests that this observation needs to be confirmed. No significant correlations were observed between myostatin expression and any muscle strength or volume measure. Although further work is necessary to clarify the findings, these data demonstrate that myostatin mRNA levels are reduced in response to heavy-resistance ST in humans.

Effect of strength training on resting metabolic rate and physical activity: age and gender comparisons.

PURPOSE The purpose of this study was to compare age and gender effects of strength training (ST) on resting metabolic rate (RMR), energy expenditure of physical activity (EEPA), and body composition. METHODS RMR and EEPA were measured before and after 24 wk of ST in 10 young men (20-30 yr), 9 young women (20-30 yr), 11 older men (65-75 yr), and 10 older women (65-75 yr). RESULTS When all subjects were pooled together, absolute RMR significantly increased by 7% (5928 +/- 1225 vs 6328 +/- 1336 kJ.d-1, P < 0.001). Furthermore, ST increased absolute RMR by 7% in both young (6302 +/- 1458 vs 6719 +/- 1617 kJ x d(-1), P < 0.01) and older (5614 +/- 916 vs 5999 +/- 973 kJ x d(-1), P < 0.05) subjects, with no significant interaction between the two age groups. In contrast, there was a significant gender x time interaction (P < 0.05) for absolute RMR with men increasing RMR by 9% (6645 +/- 1073 vs 7237 +/- 1150 kJ x d(-1), P < 0.001), whereas women showed no significant increase (5170 +/- 884 vs 5366 +/- 692 kJ x d(-1), P = 0.108). When RMR was adjusted for fat-free mass (FFM) using ANCOVA, with all subjects pooled together, there was still a significant increase in RMR with ST. Additionally, there was still a gender effect (P < 0.05) and no significant age effect (P = NS), with only the men still showing a significant elevation in RMR. Moreover, EEPA and TEE estimated with a Tritrac accelerometer and TEE estimated by the Stanford Seven-Day Physical Activity Recall Questionnaire did not change in response to ST for any group. CONCLUSIONS In conclusion, changes in absolute and relative RMR in response to ST are influenced by gender but not age. In contrast to what has been suggested previously, changes in body composition in response to ST are not due to changes in physical activity outside of training.

The ACTN3 R577X nonsense allele is under-represented in elite-level strength athletes

Previous reports have shown a lower proportion of the ACTN3 X/X genotype (R577X nonsense polymorphism) in sprint-related athletes compared to the general population, possibly attributed to impairment of muscle function related to α-actinin-3 deficiency. In the present study, we examined the frequency of the X/X genotype in both Black and White elite-level bodybuilders and strength athletes in comparison to the general population. A reference population of 668 Whites (363 men and 305 women) and 208 Blacks (98 men and 110 women) was genotyped for the ACTN3 R577X polymorphism. Strength athletes (52 white and 23 black; 4 women) consisting predominantly of world class and locally competitive bodybuilders, and elite powerlifters were recruited and similarly genotyped. Significantly lower X/X genotype frequencies were observed in the athletes (6.7%) vs controls (16.3%; P=0.005). The X/X genotype was significantly lower in White athletes (9.7%) vs controls (19.9%; P=0.018). No black athletes (0%) were observed with the X/X genotype, though this finding only approached statistical significance vs controls (4.8%; P=0.10). The results indicate that the ACTN3 R577X nonsense allele (X) is under-represented in elite strength athletes, consistent with previous reports indicating that α-actinin-3 deficiency appears to impair muscle performance.

Safety and efficacy of strength training in patients with sporadic inclusion body myositis

We studied the effects of a 12‐week progressive resistance strength training program in weakened muscles of 5 patients with sporadic inclusion body myositis (IBM). Strength was evaluated with Medical Research Council (MRC) scale ratings and quantitative isometric and dynamic tests. Changes in serum creatine kinase (CK), lymphocyte subpopulations, muscle size (determined by magnetic resonance imaging), and histology in repeated muscle biopsies were examined before and after training. After 12 weeks, the values of repetition maximum improved in the least weakened muscles, 25–120% from baseline. This dynamic effect was not captured by MRC or isometric muscle strength measurements. Serum CK, B cells, T‐cell subsets, and NK cells remained unchanged. Repeat muscle biopsies did not reveal changes in the number and degree of degenerating fibers or inflammation. The size of the trained muscles did not change. We conclude that a supervised progressive resistance training program in IBM patients can lead to gains in dynamic strength of the least weak muscles without causing muscle fatigue and muscle injury or serological, histological, and immunological abnormalities. Even though the functional significance of these gains is unclear, this treatment modality is a safe and perhaps overlooked means of rehabilitation of IBM patients.

Skeletal muscle satellite cell populations in healthy young and older men and women.

The purpose of the present investigation was to assess satellite cell populations and morphology in m. vastus lateralis biopsies obtained from young (20–30 years) and older (65–75 years) healthy, sedentary men and women. Multiple muscle biopsies were obtained from 14 young individuals (men, n = 7; women, n = 7) and 15 older individuals (men, n = 8; women, n = 7). Muscle fibers were viewed longitudinally using a Zeiss EM 10 CA electron microscope. All myonuclei and satellite cells were counted and satellite cells were photographed for morphological analysis. The proportion of satellite cells [satellite cells/(myonuclei + satellite cells)] did not differ among the four subject groups (1.7–2.8%), nor did proportions differ when subject groups were combined for age and gender comparisons. Few morphological differences were noted between groups; however, lipofuscin granules were more prominent in satellite cells from older subjects and women demonstrated significantly larger satellite cell and satellite cell nucleus areas than men. Mitochondria from satellite cells (regardless of group) were more pallid and exhibited fewer cristae than mitochondria located in the adjacent muscle fiber. The results of the current investigation suggest that, despite findings in animal models, satellite cell populations are not significantly lower in healthy, sedentary older compared to young adult men and women. Anat Rec 260:351–358, 2000.

Muscle Size Responses to Strength Training in Young and Older Men and Women

OBJECTIVES: To examine the possible influences of age and gender on muscle volume responses to strength training (ST).