Adaptations in human muscle sarcoplasmic reticulum to prolonged submaximal training

muscle sarcoplasmic reticulum to prolonged submaximal training. J Appl Physiol 94: 2034–2042, 2003; 10.1152/jappl-physiol.00244.2002.—In this study, we employed single-leg submaximal cycle training, conducted over a 10-wk period, to investigate adaptations in sarcoplasmic reticulum (SR) Ca2-regulatory proteins and processes of the vastus latera-lis. During the final weeks, the untrained volunteers (age 21.4 0.3 yr; means SE, n 10) were exercising 5 times/wk and for 60 min/session. Analyses were performed on tissue extracted by needle biopsy 4 days after the last training session. Compared with the control leg, the trained leg displayed a 19 % reduction (P 0.05) in homogenate maximal Ca2-ATPase activity (192 11 vs. 156 18 mol g protein1 min1), a 4.3 % increase (P 0.05) in pCa50, defined as the Ca2 concentration at half-maxima