Effect of sprint training on resting serum irisin concentration - Sprint training once daily vs. twice every other day.

Objective: Exercise twice every other day has been shown to lead to increasing peroxisome proliferator receptor γ coactivator-1α (PGC-1α) expression (up-stream factor of irisin) via lowered muscle glycogen level during second of exercise compared with exercise once daily. This study determined the influence of 4weeks of sprint training (training once daily vs. twice every other day) on the serum irisin concentration.

Materials And Methods: Twenty healthy males (20.9±1.3years) were assigned randomly to either the SINGLE or REPEATED group (n=10 per group). The subjects in the SINGLE group participated in a sprint training session once daily (5days per week), whereas those in the REPEATED group performed two consecutive training sessions on the same day with a 1-h rest between sessions (2-3days per week). Both groups completed 20 training sessions over 4weeks. Each training session consisted of three consecutive 30-s maximal pedaling exercises with a 10-min rest between sets. Blood samples were collected before and after training period (48h after completing the last training session).

Results: The serum irisin concentration decreased significantly after training in each group (SINGLE, 338.5±77.8 to 207.6±64.6ng/mL; REPEATED, 329.5±83.9 to 234.2±72.8ng/mL, p<0.05). The plasma interleukin-6 (IL-6) concentration tended to be lower after training in both groups (main effect for period, p=0.054). However, there was no significant difference in the serum irisin or plasma IL-6 concentration between groups after training. The serum high-molecular-weight adiponectin concentration did not change significantly after training in either group.

Conclusion: Sprint training for 4weeks significantly decreased the resting serum irisin concentration, despite different training programs (training once daily vs. twice every other day).