Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training.
Level 3 - non-randomized controlled study
Prospective cohort study analyzing correlations between acute physiological responses and training outcomes
PubMed 22105707 · doi:10.1007/s00421-011-2246-z
What was done
In a 12-week resistance training study of 56 young men, researchers evaluated acute post-exercise serum concentrations (area under the curve, AUC) of growth hormone (GH), free testosterone (fT), insulin-like growth factor 1 (IGF-1), and cortisol following an intense leg exercise session at the study midpoint. These acute systemic hormonal responses were correlated with 12-week adaptations: lean body mass (LBM), muscle fiber cross-sectional area (CSA, types I and II), and leg press strength.
What was found
No significant correlations were observed between exercise-induced AUC elevations of GH, fT, or IGF-1 and gains in LBM or leg press strength. Cortisol AUC weakly correlated with changes in LBM (r = 0.29, P < 0.05) and type II fiber CSA (r = 0.35, P < 0.01). GH AUC weakly correlated with gains in fiber CSA (type I: r = 0.36, P = 0.006; type II: r = 0.28, P = 0.04), but not LBM. No hormone correlated significantly with changes in strength.
Why it matters
The results challenge the hypothesis that transient exercise-induced surges in systemic anabolic hormones drive resistance training-induced muscle hypertrophy or strength adaptations.
Limits
The study included only young men, limiting generalizability to women and older populations. Hormonal response was assessed at only a single workout at the study midpoint rather than monitored across the entire training period, and correlational data cannot assess local intramuscular signaling pathways.
Cited by
- supports Acute transient systemic hormonal spikes resulting from resistance training have little to no meaningful effect on muscle hypertrophy.