Effect of consecutive repeated sprint and resistance exercise bouts on acute adaptive responses in human skeletal muscle

Coffey VG, Jemiolo B, Edge J, Garnham AP, Trappe SW, Hawley JA. Effect of consecutive repeated sprint and resistance exercise bouts on acute adaptive responses in human skeletal muscle. Am J Physiol Regul Integr Comp Physiol 297: R1441-R1451, 2009. First published August 19, 2009; doi: 10.1152/ajpregu.00351.2009.-We examined acute molecular responses in skeletal muscle to repeated sprint and resistance exercise bouts. Six men [age, 24.7 +/- 6.3 yr; body mass, 81.6 +/- 7.3 kg; peak oxygen uptake, 47 +/- 9.9 ml . kg(-1) . min(-1); one repetition maximum (1-RM) leg extension 92.2 +/- 12.5 kg; means +/- SD] were randomly assigned to trials consisting of either resistance exercise (8 x 5 leg extension, 80% 1-RM) followed by repeated sprints (10 x 6 s, 0.75 N . m torque . kg(-1)) or vice-versa. Muscle biopsies from vastus lateralis were obtained at rest, 15 min after each exercise bout, and following 3-h recovery to determine early signaling and mRNA responses. There was divergent exercise order-dependent phosphorylation of p70 S6K (S6K). Specifically, initial resistance exercise increased S6K phosphorylation (similar to 75% P < 0.05), but there was no effect when resistance exercise was undertaken after sprints. Exercise decreased IGF-I mRNA following 3-h recovery (similar to 50%, P = 0.06) independent of order, while muscle RING finger mRNA was elevated with a moderate exercise order effect (P < 0.01). When resistance exercise was followed by repeated sprints PGC-1 alpha mRNA was increased (REX1-SPR2; P = 0.02) with a modest distinction between exercise orders. Repeated sprints may promote acute interference on resistance exercise responses by attenuating translation initiation signaling and exacerbating ubiquitin ligase expression. Indeed, repeated sprints appear to generate the overriding acute exercise-induced response when undertaking concurrent repeated sprint and resistance exercise. Accordingly, we suggest that sprint-activities are isolated from resistance training and that adequate recovery time is considered within periodized training plans that incorporate these divergent exercise modes.