How does acute caffeine ingestion affect maximal strength and muscular power in bench press and back squat in...

This study examined whether caffeine (4 mg/kg) enhances upper- and lower-body maximal strength and muscular power by increasing muscle recruitment and reducing in ratings of perceived exertion (RPE) and pain perception.

Fourteen resistance-trained males completed two randomized trials involving either caffeine ingestion (4 mg/kg) or a placebo. Sixty minutes after ingesting capsule, participants performed maximal strength tests (one-maximum repetition [1RM]) followed by muscular power assessments (bar velocity and power output) at 25%, 50%, 75%, and 90% of 1RM, performing 3, 2, 1, and 1 repetitions, respectively during bench press and back squat. Outcome measured included 1RM, mean and peak velocity, mean and peak power output, surface electromyographic activity of the prime movers, RPE, and pain perception.

Compared to placebo, caffeine significantly increased 1RM in both bench press and back squat, while reducing RPE and pain perception and enhancing root mean square (RMS) activity in the gluteus maximus (all p < 0.05), though it did not affect the median frequency (MDF) or mean frequency (MF) in any studied muscle (all p > 0.05). The percent improvement in 1RM was larger (+7.0 ± 2.9% vs. + 4.1 ± 2.9%; p < 0.05) for the back squat than for the bench press. Furthermore, caffeine significantly increased muscular power during both exercises (all p < 0.05), without affecting surface electromyographic activity of the prime movers, RPE, and pain perception (all p > 0.05).

Ingesting a caffeine capsule at a dose of 4 mg/kg enhances maximal strength by increasing muscle recruitment and reducing RPE and pain perception, with greater improvement observed in the bench press than in the back squat. Caffeine also improves muscular power in both exercises without altering muscle recruitment or subjective perception.