Jeffrey T. Lemmer

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.

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.

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.

Age and sex affect human muscle fibre adaptations to heavy‐resistance strength training

This study assessed age and sex effects on muscle fibre adaptations to heavy‐resistance strength training (ST). Twenty‐two young men and women (20–30 years old) and 18 older men and women (65–75 years old) completed 9 weeks of heavy‐resistance knee extension exercises with the dominant leg 3 days week−1; the non‐dominant leg served as a within‐subject, untrained control. Bilateral vastus lateralis muscle biopsies were obtained before and after ST for analysis of type I, IIa and IIx muscle fibre cross‐sectional area (CSA) and fibre type distribution. One‐repetition maximum (1‐RM) strength was also assessed before and after ST. ST resulted in increased CSA of type I, IIa and IIx muscle fibres in the trained leg of young men, type I and IIa fibres in young women, type IIa fibres in older men, and type IIx fibres in older women (all P < 0.05). Analysis of fibre type distribution revealed a significant increase in the percentage of type I fibres (P < 0.05) along with a decrease in type IIx fibres (P= 0.054) after ST only in young women. There were no significant changes in muscle fibre CSA or fibre type distribution in the untrained leg for any group. All groups displayed significant increases in 1‐RM (27–39%; all P < 0.01). In summary, ST led to significant increases in 1‐RM and type II fibre CSA in all groups; however, age and sex influence specific muscle fibre subtype responses to ST.

Regional bone mineral density after resistive training in young and older men and women.

Purpose: The purpose of this study was to determine the effects of 6 months of whole‐body resistive training (RT) on total and regional bone mineral density (BMD) and bone mineral content (BMC) by age and gender in young and older men and women.

Strength Training Normalizes Resting Blood Pressure in 65- to 73-Year-Old Men and Women with High Normal Blood Pressure

OBJECTIVE: To determine the effects of heavy resistance strength training (ST) on resting blood pressure (BP) in older men and women.

Age and Sex Differentially Affect Regional Changes in One Repetition Maximum Strength

To assess the influences of age and sex on regional changes in 1 repetition maximum (1RM) strength, 10 young men (20–30 years), 8 young women (20–30 years), 11 older men (65–75 years), and 10 older women (65–75 years) were studied before and after a 24-week whole-body strength training program. Changes in 1RM strength were analyzed for each individual exercise, as well as by calculating a total body score (TBS), an upper body score (UBS), and a lower body score (LBS). The effect of age and sex on changes in 1RM strength was analyzed using a repeated measures analysis of variance. When changes in strength for individual exercises were analyzed, the chest press, lat pulldown, shoulder press, and triceps pushdown were affected by both age (p > 0.05) and sex (p > 0.05), while the biceps curls were only influenced by age (p > 0.05). For the lower body, the leg press changes in 1RM strength were influenced by age (p > 0.0001), while leg extension was influenced by sex (p > 0.05). Total body score, UBS, and LBS showed significant increases with 24 weeks of ST (p > 0.001, all). Changes in TBS and UBS were affected by age (p > 0.001, both) and sex (p > 0.05 and p > 0.001, respectively). Younger subjects showed a greater increase in strength than older subjects, and men showed a greater increase in strength compared with women. Changes in LBS were affected by age (p > 0.001), with younger subjects showing a greater increase in strength compared with the older subjects, but not by sex (p = 0.464). These data indicate that regional increases in strength are differentially affected by age and sex.

Timing protein intake increases energy expenditure 24 h after resistance training.

PURPOSE To determine whether protein supplementation (PRO) before an acute bout of heavy resistance training (HRT) would influence postexercise resting energy expenditure (REE) and the nonprotein respiratory exchange ratio (RER). HYPOTHESIS REE would be increased and RER would be decreased up to 48 h after timed PRO and HRT compared with CHO supplementation and HRT. METHODS Eight resistance-trained subjects (five men and three women) participated in a double-blind two-trial crossover design, where REE and RER were measured (7:00 a.m.) on four consecutive days. On the second day of trial 1, subjects consumed 376 kJ of either PRO (18 g of whey protein, 2 g of carbohydrate, 1.5 g of fat) or CHO (1 g of whey protein, 19 g of carbohydrate, 1 g of fat) 20 min before a single bout of HRT (nine exercises, 4 sets, 70%-75% 1-repetition maximum). REE and RER were measured 24 and 48 h after HRT. During trial 2, the same protocol was followed except subjects consumed the second supplement before HRT. RESULTS Compared with baseline, REE was elevated significantly in both CHO and PRO at 24 and 48 h after HRT (P < 0.05). At 24 h after HRT, REE in response to PRO was significantly greater compared with CHO (P < 0.05). RER decreased significantly in both CHO and PRO at 24 h after HRT compared with baseline (P < 0.05). No differences were observed in total energy intake, macronutrient intake, or HRT volume (P > 0.05). CONCLUSIONS Timing PRO before HRT may be a simple and effective strategy to increase energy expenditure by elevating REE the day after HRT. Increasing REE could facilitate reductions in body fat mass and improve body composition if nutritional intake is stable.