Three weeks of sprint interval training improved high-intensity cycling performance and limited ryanodine receptor modifications in recreationally active human subjects

Purpose Mechanisms underlying the efficacy of sprint interval training (SIT) remain to be understood. We previously reported that an acute bout of SIT disrupts the integrity of the sarcoplasmic reticulum (SR) Ca2+ release channel, the ryanodine receptor 1 (RyR1), in recreationally active human subjects. We here hypothesize that in addition to improving the exercise performance of recreationally active humans, a period of repeated SIT sessions would make the RyR1 protein less vulnerable and accelerate recovery of contractile function after a SIT session. Methods Eight recreationally active males participated in a 3-week SIT program consisting of nine sessions of four-six 30-s all-out cycling bouts with 4 min of rest between bouts. Results Total work performed during a SIT session and maximal power (W-max) reached during an incremental cycling test were both increased by similar to 7.5% at the end of the training period (P < 0.05). Western blots performed on vastus lateralis muscle biopsies taken before, 1 h, 24 h and 72 h after SIT sessions in the untrained and trained state showed some protection against SIT-induced reduction of full-length RyR1 protein expression in the trained state. SIT-induced knee extensor force deficits were similar in the untrained and trained states, with a major reduction in voluntary and electrically evoked forces immediately and 1 h after SIT (P < 0.05), and recovery after 24 h. Conclusions Three weeks of SIT improves exercise performance and provides some protection against RyR1 modification, whereas it does not accelerate recovery of contractile function.