Effects of time of day on resistance exercise-induced anabolic signaling in skeletal muscle

Author： Sedliak Milan Zeman Michal Buzgó Gabriel Cvečka Ján Hamar Dušan Laczo Eugen Zelko Aurel Okuliarová Monika Raastad Truls Nilsen Tormod S. Kyröläinen Heikki Häkkinen Keijo Ahtiainen Juha P. Hulmi Juha J.

Publisher： Taylor & Francis Ltd

ISSN： 0929-1016

Source： Biological Rhythm Research, Vol.44, Iss.5, 2013-10, pp. : 756-770

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Abstract

This study examined the effect of morning versus afternoon exercise on acute responses in phosphorylation of proteins regulating muscle size and metabolism. Twenty-two untrained men, divided into the morning (n = 11) or afternoon (n = 11) group, performed maximal isometric leg extensions before and after resistance loading at 07:30–08:30 h and 16:00–17:00 h, respectively. Muscle pre- and postloading biopsies were analyzed for phosphorylated Akt, p70S6K, rpS6, p38 mitogen-activated protein kinase (MAPK), Erk1/2, and eukaryotic elongation factor (eEF) 2. Muscle force declined after exercise in both groups (p < 0.001). p70S6K Thr³⁸⁹ (p < 0.05) and Thr⁴²¹/Ser⁴²⁴ and rpS6 (all p < 0.001) increased after exercise in both groups. The afternoon but not morning group showed postloading decrease (p < 0.05) and increase (p < 0.01) in eEF2 and p38MAPK, respectively. Akt and Erk1/2 were statistically unchanged. In conclusion, the time of day did not have an overall effect on protein synthesis signaling, but morning phosphorylated eEF2 and p38MAPK showed significantly larger between-subject variability in the exercise response compared to the afternoon.