Androgen and Glucocorticoid Receptor Phosphorylation Following Resistance Exercise and Pre-Workout Supplementation.

PURPOSE Consumption of caffeine or caffeine containing pre-workout supplements (SUPP) augments steroid hormone responses to resistance exercise (RE). However, the activation of glucocorticoid (GR) and androgen receptors (AR) following RE SUPP has not been investigated. The purpose of this study was to determine the influence of a pre-workout supplement on AR and GR phosphorylation following RE. METHODS In a randomized, counter-balanced, double-blind, placebo-controlled, within-subject crossover study, ten resistance-trained males ((X¯±SD, age=22±2.4 yrs, hgt=175±7 cm, body mass=84.1±11.8kg) performed four sets of 8 repetitions of barbell back squats at 75% of their 1-repetition maximum (1-RM) with two minutes of rest between sets and a fifth set of barbell back squats at 60% of 1-RM until concentric failure. A SUPP or flavor and color matched placebo (PL) was consumed 60-minutes prior to RE. Vastus lateralis muscle biopsies were obtained prior to supplementation at rest (BL), and ten minutes post-exercise (POST). Biopsies were analyzed for phosphorylated GR (ser134, ser211, and ser226) and phosphorylated AR (ser81, ser213, ser515, ser650) via western blotting. RESULTS pGRser134 decreased, and pGRser226 increased following RE (p 0.05). pGRser211 was unchanged after RE (p>0.05). pARser515 increased, and total AR expression decreased after RE (p 0.05). CONCLUSION RE influences AR and GR phosphorylation, and SUPP minimally influences this response in the early recovery period.