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.

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. METHODS: Younger men (n=10) and women (n=7) aged 20-29 years (25+/-1 years) and older men (n=10) and women (n=10) aged 65-74 years (69+/-1 years) participated in 6 months of progressive whole-body RT. Upper- and lower-body strength was assessed by the one repetition maximum (1RM) test, and total body fat, lean tissue mass, femoral neck BMD, Ward's triangle BMD, greater trochanter BMD, total-body BMD, and L2-L4 spine BMD were determined by dual-energy X-ray absorptiometry before and after 6 months of RT. RESULTS: Percent body fat decreased only in the young men (P<0.05). Lean tissue mass increased after training in young men and women and older men (P<0.05) but did not change significantly in older women. Upper- and lower-body 1RM strength increased in all groups (P<0.01). Overall, there was a significant increase in BMD at the femoral neck, ward's triangle and greater trochanter BMD, as well as total body BMC and leg BMC (P<0.05). Total-body BMD and L2-L4 spine BMD did not change with RT. There were no gender differences in the training response between men and women for any of the BMD regions and no age differences in the training response, except for a trend between young and older subjects for femoral neck (P<0.08). CONCLUSION: A 6-month RT program increases muscle mass and improves BMD of the femoral region in young and healthy older men and women as a group, with a trend for this to be greater in young subjects.