Muscle Hypotrophy

This randomized, double-blind, placebo-controlled crossover trial investigates the effects of three different caffeine supplementation strategies on resistance training-induced adaptations in 180 caffeine-naive, inactive young adult males. Participants will undergo two 4-week supervised resistance training programs separated by a 2-week washout/crossover period. The three caffeine strategies are: (1) constant daily low-moderate dosing (3 mg/kg/day), (2) gradually escalating dose (3 to 6 mg/kg across weeks), and (3) training-day-only caffeine (3 mg/kg/day). Primary outcomes include non-invasive measures of integrated anabolism and hypertrophy (D2O-derived plasma proteomic fractional synthesis rate, DXA muscle volume) and strength metrics. Secondary outcomes include hormonal responses (insulin, cortisol, testosterone, IGF-1), sleep/recovery parameters, and adverse effects.