Resistance Training Adaptations and Caffeine Intake

This parallel-group, randomized, double-blind, placebo-controlled trial investigates the effects of three different caffeine supplementation strategies on resistance training-induced adaptations in 120 caffeine-naive, inactive young adult males. Participants will undergo a 10-week supervised resistance training program. The four supplementation strategies are: (1) constant daily low-moderate dosing (4 mg/kg/day), (2) gradually escalating dose (2 to 6 mg/kg across weeks), (3) training-day-only caffeine (4 mg/kg/day), and (4) placebo. Primary outcomes include maximal strength, body composition (lean body mass and fat mass), skeletal muscle thickness, and training volume progression. Secondary outcomes include muscular endurance, jump height, flight-time-to-contraction-time (FT:CT) ratio, mechanistic/biological variables (epinephrine, norepinephrine, cortisol, testosterone, creatine kinase, IGF-1), rate of perceived exertion, sleep/recovery parameters, and adverse effects.