Immobilization effects in young and older adults.

This experiment compared the effects of disuse on the adductor pollicis (AP) muscle in young (YM) and old (OM) men. The AP of the YM and OM was assessed for strength (MVC), compound muscle action potential (CMAP), and volume, and then immobilized for 2 weeks. MVC decreased approximately 22% in the YM, and OM (P<0.001). AP volume was 4.1% (not significant) and 9.5% (P<0.05) less in the YM and OM, respectively. CMAP increased in the OM 0, 24, and 48 h post-immobilization, and did not change in the YM. However, the YM showed a greater decrease in specific force as compared to the OM. YM and OM experienced similar losses in strength, yet muscle volume loss was only significant in OM. Although OM are more susceptible to immediate losses in muscle volume, muscle activation strategies appear to preserve strength during atrophy.