Resistance training improves single muscle fiber contractile function in older women

Abstract

The purpose of this study was to 1) examine single cell contractile mechanics of skeletal muscle before and after 12 wk of progressive resistance training (PRT) in older women (n = 7; 74 +/- 2 yr) and 2) to compare these results to our previously completed single cell PRT work with older men (n = 7; 74 +/- 2 yr) (Trappe S, Williamson D, Godard M, Porter D, Rowden G, and Costill D. J Applied Physiol 89:143--152, 2000). Knee extensor PRT was performed 3 days/wk at 80% of one-repetition maximum. Muscle biopsies were obtained from the vastus lateralis before and after the PRT. Chemically skinned single muscle fibers (n = 313) were studied at 15 degrees C for peak tension (P(o)), unloaded shortening velocity (V(o)), and power. Due to the low number of hybrid fibers identified post-PRT, direct comparisons were limited to MHC I and IIa fibers. Muscle fiber diameter increased 24% (90 +/- 2 to 112 +/- 6 microm; P < 0.05) in MHC I fibers with no change in MHC IIa fibers. P(o) increased (P < 0.05) 33% in MHC I (0.76 +/- 0.04 to 1.01 +/- 0.09 mN) and 14% in MHC IIa (0.73 +/- 0.04 to 0.83 +/- 0.05 mN) fibers. Muscle fiber V(o) was unaltered in both fiber types with PRT. MHC I and IIa fiber power increased (P < 0.05) 50% [11 +/- 2 to 17 +/- 2 microN. fiber length (FL). s(-1)] and 25% (40 +/- 8 to 51 +/- 6 microN. FL. s(-1)), respectively. However, when peak power was normalized to cell size, no pre- to postimprovements were observed. These data indicate that PRT in elderly women increases muscle cell size, strength, and peak power in both slow and fast muscle fibers, which was similar to the older men. However, in contrast to the older men, no change in fiber V(o) or normalized power was observed in the older women. These data suggest that older men and women respond differently at the muscle cell level to the same resistance-training stimulus.

Aerobic exercise training improves whole muscle and single myofiber size and function in older women

“…Individual muscle fibers were analyzed for diameter, peak force (Po), shortening velocity (Vo), and power characteristics. Detailed descriptions and illustrations of these procedures have been presented in our laboratory's previous work (45,46).…”

Effect of Age and Gender on Muscle Function-Analysis by Muscle Fiber Conduction Velocity-

“…Delays in MFCV due to aging are thus less likely to occur in males than in females. Trappe 32) described that, particularly in elderly females, motion speed of daily living becomes slower in most of the cases, and that as Type I fibers are often mobilized at the time initiating motion, the function of Type I fibers is maintained. This may account for why the degree of delay in MFCV due to aging is lower in females than in males.…”

Efeitos do treinamento de força sobre os níveis de IGF1 e de força muscular nas fases neurogência e miogênica de idosas

“…17 Portanto, a estimulação do IGF1 contribuirá de forma significativa para a hipertrofia e para o aumento do conteúdo de miofibrilas esqueléticas. 18 O presente estudo teve por objetivo avaliar os efeitos do treinamento de força sobre os níveis basais de IGF1 e de força muscular nas fases neurogência e miogênica de idosas sedentárias.…”