Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors

Abstract

The aim of our study was to determine whether resistance exercise-induced elevations in endogenous hormones enhance muscle strength and hypertrophy with training. Twelve healthy young men (21.8 +/- 1.2 yr, body mass index = 23.1 +/- 0.6 kg/m(2)) trained their elbow flexors independently for 15 wk on separate days and under different hormonal milieu. In one training condition, participants performed isolated arm curl exercise designed to maintain basal hormone concentrations (low hormone, LH); in the other training condition, participants performed identical arm exercise to the LH condition followed immediately by a high volume of leg resistance exercise to elicit a large increase in endogenous hormones (high hormone, HH). There was no elevation in serum growth hormone (GH), insulin-like growth factor (IGF-1), or testosterone after the LH protocol but significant (P < 0.001) elevations in these hormones immediately and 15 and 30 min after the HH protocol. The hormone responses elicited by each respective exercise protocol late in the training period were similar to the response elicited early in the training period, indicating that a divergent postexercise hormone response was maintained over the training period. Muscle cross-sectional area (CSA) increased by 12% in LH and 10% in HH (P < 0.001) with no difference between conditions (condition x training interaction, P = 0.25). Similarly, type I (P < 0.01) and type II (P < 0.001) muscle fiber CSA increased with training with no effect of hormone elevation in the HH condition. Strength increased in both arms, but the increase was not different between the LH and HH conditions. We conclude that exposure of loaded muscle to acute exercise-induced elevations in endogenous anabolic hormones enhances neither muscle hypertrophy nor strength with resistance training in young men.

Fig. 1.

Whole blood lactate (A) and serum growth hormone (GH; B), IGF-1 (C), total testosterone (D), free testosterone (E) and cortisol (F) concentrations at rest and after low hormone (LH) and high hormone (HH) exercise protocols. Insets: net area under the curve (AUC; rest = 0); closed bars, HH; open bars, LH. Significantly greater than LH for corresponding time points and for AUC, *P < 0.01, †P < 0.001. Values are means ± SE.

Fig. 2.

Maximal voluntary contraction (MVC; A), one-repetition maximum (1 RM; B), and 10-repetition maximum (10 RM; C) before and after training in LH and HH. *Main effect of training, P < 0.001; there were no interactions (training × condition) for any strength measure (P = 0.65, 0.43, 0.63 for MVC, 1 RM and 10 RM, respectively). Values are means ± SE.

Fig. 3.

Type I (A) and II fiber (B) cross-sectional area (CSA) of the biceps brachii before (Pre) and after (Post) training in LH and HH; main effect of training, *P < 0.01, †P < 0.001. Elbow flexor CSA before and after training (C) in LH and HH; main effect of training, †P < 0.001. Elbow flexor CSA as a function of distance from the elbow joint line before and after training (D) in LH and HH; main effect of training, †P < 0.001. There were no interactions (training × condition) for either fiber or whole muscle CSA (type I, P = 66; type II, P = 0.55; CSA, P = 0.27). Values are means ± SE.