Effects of hindlimb suspension on contractile properties of young and old rat muscles and the impact of electrical stimulation on the recovery process

The purpose of this study was to investigate the effects of hindlimb suspen sion (HS) on contractile properties of skeletal muscles of young and old ra ts and to determine the impact of electrical stimulation (ES) on the qualit y and degree of recovery of these muscles. After 21 days of HS, young soleu s (SOL) muscle became faster, but there was no impact on young extensor dig itorum longus (EDL) muscle. Twitch tension (Pt) decreased 61% in young and 70% in old SOL muscles. Specific tetanic tension (Po) decreased 53% in youn g and 64% in old SOL muscles, but again there was no impact on EDL muscle. After a 14-day period of recovery, contraction time (CT), half-relaxation t ime (RT1/2), Pt and Po returned to control group values in both young and o ld SOL muscles. Measurements of the contractile properties of young and old skeletal rat muscles showed ES sometimes to be beneficial but also sometim es to be harmful. A 14-day period of recovery, with or without ES, seemed s ufficient for many variables to return to control group values. (C) 1999 El sevier Science Ireland Ltd. All rights reserved.