Human skeletal sarcoplasmic reticulum Ca2+ uptake and muscle function withaging and strength training

This study investigated the adaptations of skeletal muscle sarcoplasmic ret iculum (SR) Ca2+ uptake, relaxation, and fiber types in young (YW) and elde rly women (EW) to high-resistance training. Seventeen YW (18-32 yr) and 11 EW (64-79 yr) were assessed for 1) electrically evoked relaxation time and rate of the quadriceps femoris; and 2) maximal rates of SR Ca2+ uptake and Ca2+-ATPase activity and relative fiber-type areas, analyzed from muscle bi opsies of the vastus lateralis. EW had significantly slower relaxation rate s and times, decreased SR Ca2+ uptake and Ca2+-ATPase activity, and a large r relative type I fiber area than did YW. A subgroup of 9 young (YWT) and 1 0 elderly women (EWT) performed 12 wk of high-resistance training (8 repeti tion maximum) of the quadriceps and underwent identical testing procedures pre- and posttraining. EWT significantly increased their SR Ca2+ uptake and Ca2+-ATPase activity in response to training but showed no alterations in speed of relaxation or relative fiber-type areas. In YWT none of the variab les was altered after resistance training. These findings suggest that 1) a reduced SR Ca2+ uptake in skeletal muscle of elderly women was partially r eversed with resistance training and 2) SR Ca2+ uptake in the vastus latera lis was not the rate-limiting mechanism for the slowing of relaxation measu red from electrically evoked quadriceps muscle of elderly women.