Enhanced sarcoplasmic reticulum Ca2+ release following intermittent sprinttraining

To evaluate the effect of intermittent sprint training on sarcoplasmic reti culum (SR) function, nine young men performed a 5 wk high-intensity intermi ttent bicycle training, and six served as controls. SR function was evaluat ed from resting vastus lateralis muscle biopsies, before and after the trai ning period. Intermittent sprint performance (ten 8-s all-out periods alter nating with 32-s recovery) was enhanced 12% (P < 0.01) after training. The 5-wk sprint training induced a significantly higher (P < 0.05) peak rate of AgNO3-stimulated Ca2+ release from 709 (range 560-877; before) to 774 (596 -977) arbitrary units Ca2+ . g protein(-1) . min(-1) (after). The relative SR density of functional ryanodine receptors (RyR) remained unchanged after training; there was, however, a 48% (P < 0.05) increase in total number of RyR. No significant differences in Ca2+ uptake rate and Ca2+-ATPase capaci ty were observed following the training, despite that the relative density of Ca2+-ATPase isoforms SERCA1 and SERCA2 had increased 41% and 55%, respec tively (P, 0.05). These data suggest that high-intensity training induces a n enhanced peak SR Ca2+ release, due to an enhanced total volume of SR, whe reas SR Ca2+ sequestration function is not altered.