Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 27174923 · doi:10.1152/japplphysiol.00154.2016
What was done
Forty-nine resistance-trained young men (mean age 23 ± 1 years) were randomly assigned to 12 weeks of whole-body resistance training performed to volitional failure using either higher repetitions with lower loads (30–50% 1RM, 20–25 reps/set, n = 24) or lower repetitions with higher loads (75–90% 1RM, 8–12 reps/set, n = 25). Outcomes assessed before and after training included 1RM strength, DXA-derived lean body mass, type I and type II muscle fiber cross-sectional area via muscle biopsies, and acute postexercise systemic hormone concentrations.
What was found
Both groups significantly increased 1RM strength across all tested exercises (P < 0.01), with the lower-repetition (higher-load) group achieving significantly greater strength gains in the bench press (14 ± 1 kg vs. 9 ± 1 kg, P = 0.012). Fat- and bone-free lean mass and type I and type II muscle fiber cross-sectional area increased significantly in both groups (P < 0.01) with no significant between-group differences. Acute postexercise rises in systemic hormones did not correlate with changes in muscle hypertrophy or strength.
Why it matters
This trial demonstrates that lifting load does not determine muscle hypertrophy in trained individuals when sets are performed to failure, and that transient systemic hormonal spikes after exercise do not drive muscle growth or strength.
Limits
The study included only young, resistance-trained men across a 12-week intervention, limiting generalizability to women, older adults, or longer training periods. Specific numeric values for total lean mass gains, individual fiber area changes, and specific hormone levels were omitted from the abstract.