Age-Related Changes in Skeletal Muscle Activation Following Short-Term Resistance Training

Abstract

PURPOSE: To determine the effects of short-term resistance training on measures of muscular strength and skeletal muscle activation of the triceps surae in adult males from 20-79 years of age. METHODS: Forty-six subjects volunteered for this study and were designated into one of three groups, classified as individuals aged between 20-39 years (GI, n=20), 40-59 years (GII, n=16), and 60-79 years (GIII, n=10). Subjects participated in three supervised resistance training sessions over the course of seven days, performing four lower body exercises during each training session. Subjects were assessed for muscle cross-sectional area (CSA), maximal isometric strength (ISO), antagonist co-activation (ANTCO), and muscle activation determined through twitch interpolation (VA%) and surface electromyography (SEMG). Two-way repeated measures ANOVA was used to determine group differences and changes with training. RESULTS: Analysis of baseline data revealed a significant difference (p=0.007) in ISO between GI (127.9 ± 5.5 nm) and GIII (99.8 ± 7.5 nm) for plantarflexion maximal strength. No significant differences (p>0.05) were observed for CSA, ANTCO, VA%, or SEMG between groups. Following training, there was no significant change (p>0.05) in CSA, ISO, ANTCO, or VA% for any age group. Examination of SEMG data determined significant main effects for muscle group (p=0.001) and time (p=0.013) for amplitude. A significant decrease for the time main effect (p=0.001) in SEMG median frequency was also observed post-training. CONCLUSIONS: The results from the present study indicated that there were no significant pre-test to post-test changes in muscle size, muscular strength, antagonist co-activation, or muscle activation following the experimental training period for any group. These findings were unlike those from previous investigations of the leg extensors that have reported improvements in neuromuscular performance after only two or three training sessions. This data may be useful for those involved in rehabilitative programs suggesting the muscles of the lower limb could require more than three training sessions to elicit the neuromuscular adaptations that typically occur during the early stages of a resistance training program.