Skeletal muscle satellite cell characteristics in young and older men and women after heavy resistance strength training

Skeletal muscle satellite cell proportions and morphology were assessed in healthy, sedentary young and older men and women in response to heavy resis tance strength training (HRST). Fourteen young (20-30 years) men (n = 7) an d women (n = 7) and 15 older (65-75 years) men (n = 8) and women (n = 7) co mpleted 9 weeks of unilateral knee extension exercise training 3 days per w eek. Muscle biopsies were obtained from each vastus lateralis before and af ter training, with the nondominant leg serving as an untrained control. All four groups demonstrated a significant increase in satellite cell proporti on in response to HRST (2.3 +/- 0.4% vs 3.1 +/- 0.4% for ail subjects combi ned, before and after training, respectively; p < .05), with older women de monstrating the greatest increase (p < .05). Morphology data indicated a si gnificant increase in the proportion of active satellite cells in after-tra ining muscle samples compared with before-training samples and with control leg samples (31% vs 6% and 7%, respectively; p < .05). The present results indicate that the proportion of satellite cells is increased after HRST in young and older men and women, with an exaggerated response in older women . Furthermore, the proportion of satellite cells that appear morphologicall y active is increased as a result of HRST.