Consecutive bouts of diverse contractile activity alter acute responses in human skeletal muscle

Coffey VG, Pilegaard H, Garnham AP, O'Brien BJ, and Hawley JA. Consecutive bouts of diverse contractile activity alter acute responses in human skeletal muscle. J Appl Physiol 106: 1187-1197, 2009. First published January 22, 2009; doi:10.1152/japplphysiol.91221.2008.-We examined acute molecular responses in skeletal muscle to divergent exercise stimuli by combining consecutive bouts of resistance and endurance exercise. Eight men [22.9 +/- 6.3 yr, body mass of 73.2 +/- 4.5 kg, peak O-2 uptake ((V) over dot(O2peak)) of 54.0 +/- 5.7 ml.kg(-1).min(-1)] were randomly assigned to complete trials consisting of either resistance exercise (8 x 5 leg extension, 80% 1 repetition maximum) followed by a bout of endurance exercise (30 min cycling, 70% (V) over dot(O2peak)) or vice versa. Muscle biopsies were obtained from the vastus lateralis at rest, 15 min after each exercise bout, and after 3 h of passive recovery to determine early signaling and mRNA responses. Phosphorylation of Akt and Akt1(Ser473) were elevated 15 min after resistance exercise compared with cycling, with the greatest increase observed when resistance exercise followed cycling (similar to 55%; P < 0.01). TSC2-mTOR-S6 kinase phosphorylation 15 min after each bout of exercise was similar regardless of the exercise mode. The cumulative effect of combined exercise resulted in disparate mRNA responses. IGF-I mRNA content was reduced when cycling preceded resistance exercise (-42%), whereas muscle ring finger mRNA was elevated when cycling was undertaken after resistance exercise (similar to 52%; P < 0.05). The hexokinase II mRNA level was higher after resistance cycling (similar to 45%; P < 0.05) than after cycling-resistance exercise, whereas modest increases in peroxisome proliferator-activated receptor gamma coactivator-1 alpha mRNA did not reveal an order effect. We conclude that acute responses to diverse bouts of contractile activity are modified by the exercise order. Moreover, undertaking divergent exercise in close proximity influences the acute molecular profile and likely exacerbates acute interference.