In guys who are new to weightlifting, a spike in a certain body chemical (IL-6) right after a workout is linked to bigger muscles after 16 weeks of training—but that spike alone doesn’t fully explain why some guys get bigger than others, because other internal changes in the muscle also matter.

A prospective, longitudinal RCT in young, untrained males where participants undergo standardized resistance training for 16 weeks, with serial blood draws to measure acute post-exercise IL-6 spikes and muscle biopsies to assess intramuscular AR and p70S6K changes; muscle hypertrophy is measured via DEXA or MRI at baseline and endpoint; multivariate regression is used to test whether IL-6 spike independently predicts hypertrophy after adjusting for AR and p70S6K changes.

A prospective cohort study tracking young untrained males undergoing self-selected or standardized resistance training over 16 weeks, measuring acute IL-6 responses after each session, intramuscular AR and p70S6K changes via biopsy at baseline and endpoint, and muscle growth via imaging; statistical models test whether IL-6 response predicts hypertrophy after controlling for AR and p70S6K.

Analysis of existing data from a prior 16-week resistance training study in young untrained males, where acute IL-6, intramuscular AR, p70S6K, and hypertrophy data were collected; researchers re-analyze the dataset using multivariate regression to test whether IL-6 spike independently predicts hypertrophy after adjusting for AR and p70S6K.

A case-control study comparing young untrained males who achieved high vs. low muscle hypertrophy after 16 weeks of resistance training, examining whether those with higher hypertrophy had significantly greater acute IL-6 responses and whether this difference persists after adjusting for intramuscular AR and p70S6K levels.