Resistance exercise-induced hormonal response promotes satellite cell proliferation in untrained men but not in women

The purpose of this work was to determine the effect of resistance exercise (RE)-induced hormonal changes on the satellite cell (SC) myogenic state in response to muscle damage. Untrained men (n = 10, 22-3 yr) and women (n = 9, 21-4 yr) completed 2 sessions of 80 unilateral maximal eccentric knee extensions followed by either an upper body RE protocol (EX) or a 20-min rest (CON). Muscle samples were collected and analyzed for protein content of Pax7, MyoD, myogenin, cyclin D1, and p21 before (PRE), 12 h, and 24 h after the session was completed. Serum testosterone, growth hormone, cortisol, and myoglobin concentrations were analyzed at PRE, post-damage, immediately after (IP), and 15, 30, and 60 min after the session was completed. Testosterone was significantly (P < 0.05) higher immediately after the session in EX vs. CON for men. A significant time ☓ sex ☓ condition interaction was found for MyoD with an increase in EX (men) and CON (women) at 12 h. A significant time ☓ condition interaction was found for Pax7, with a decrease in EX and increase in CON at 24 h. A significant time effect was found for myogenin, p21, and cyclin D1. Myogenin and p21 were increased at 12 and 24 h, and cyclin D1 was increased at 12 h. These results suggest that the acute RE-induced hormonal response can be important for men to promote SC proliferation after muscle damage but had no effect in women. Markers of SC differentiation appeared unaffected by the hormonal response but increased in response to muscle damage.