Background: Recent research has shown that betaine supplementation can increase strength and power performance. To further investigate the ergogenic effects of betaine supplementation a balanced, randomized, double-blind, repeated measures crossover study was designed to examine select hormonal and muscle signaling responses during supplementation. Methods: Twelve recreationally active men (age, 19.7 ± 1.23 years; height, 172.6 ± 5.61 cm; weight, 84.27 ± 15.3 kg; body fat, 18.7 ± 7.0%; BMI, 28.2 ± 4.0) with a minimum of 3 months of resistance training including back squat and bench press participated in the study. A within crossover design was utilized and subjects were randomly assigned to either betaine or placebo group. Subjects performed an acute exercise test (AET) consisting of maximal vertical jumps, isometric bench press, isometric squat, and a box lift test before and after 14 days of supplementation (twice a day) with either betaine (1.25 g dissolved in Gatorade) or placebo (same volume of Gatorade alone). During each AET, blood samples were obtained at pre, mid, post, +5, and +15 and were analyzed for GH, IGF-1 and cortisol. Also during each AET, muscle biopsies were obtained from the vastus lateralis at pre and +10 and were analyzed for select muscle signaling proteins (Total Akt, Akt S473, p70 S6k1, p70 S6k1 T389, and AMPK T172). Following a 14 day washout period, subjects crossed over to the other supplementation protocol and performed the same pre and post AETs. Results: Following betaine supplementation, there was a significant increase in isometric squat force production and number of boxes lifted during the box lift test. However, there were no significant differences in isometric bench press and vertical jumps between supplementation groups. There was a significant increase in area under the curve (AUC) for GH and IGF-1 and a significant decrease (AUC) for cortisol following 14 days of betaine supplementation. Following betaine supplementation, there was an increased in muscle Total Akt. Phosphorylation of Akt at S473 and phosphorylation of p70 S6k at T389 were maintained following betaine supplementation while these values were decreased during placebo supplementation. Phosphorylation of AMPK at T172 was decreased following betaine and placebo supplementation. Conclusion: Betaine supplementation increased force production and muscular endurance. These performance measures correspond to increases in anabolic hormones (GH and IGF-1) and maintenance of anabolic muscle signaling (Total Akt, Akt and p70 S6k phosphorylation) responses, as well as the decrease in catabolic hormone (cortisol) and inhibitory muscle signaling (AMPK phosphorylation) following 14 days of betaine supplementation.
