Neuromuscular responses to incremental caffeine doses: performance and side effects

• Published in: Medicine and science in sports and exercise Vol. 45; no. 11; p. 2184
• Main Authors: Pallarés, Jesús G, Fernández-Elías, Valentín E, Ortega, Juan F, Muñoz, Gloria, Muñoz-Guerra, Jesús, Mora-Rodríguez, Ricardo
• Format: Journal Article
• Language: English
• Published: United States 01.11.2013
• Subjects: Adult; Athletic Performance - physiology; Caffeine - administration & dosage; Caffeine - adverse effects; Caffeine - metabolism; Central Nervous System Stimulants - administration & dosage; Central Nervous System Stimulants - adverse effects; Central Nervous System Stimulants - metabolism; Cross-Over Studies; Double-Blind Method; Gastrointestinal Diseases - chemically induced; Headache - chemically induced; Humans; Male; Muscle Strength - drug effects; Muscle, Skeletal - physiology; Myalgia - chemically induced; Tachycardia - chemically induced; Urine; Weight Lifting - physiology; Young Adult
• DOI: 10.1249/MSS.0b013e31829a6672

The purpose of this study was to determine the oral dose of caffeine needed to increase muscle force and power output during all-out single multijoint movements. Thirteen resistance-trained men underwent a battery of muscle strength and power tests in a randomized, double-blind, crossover design, under four different conditions: (a) placebo ingestion (PLAC) or with caffeine ingestion at doses of (b) 3 mg · kg(-1) body weight (CAFF 3mg), (c) 6 mg · kg(-1) (CAFF 6mg), and (d) 9 mg · kg(-1) (CAFF 9mg). The muscle strength and power tests consisted in the measurement of bar displacement velocity and muscle power output during free-weight full-squat (SQ) and bench press (BP) exercises against four incremental loads (25%, 50%, 75%, and 90% one-repetition maximum [1RM]). Cycling peak power output was measured using a 4-s inertial load test. Caffeine side effects were evaluated at the end of each trial and 24 h later. Mean propulsive velocity at light loads (25%-50% 1RM) increased significantly above PLAC for all caffeine doses (5.4%-8.5%, P = 0.039-0.003). At the medium load (75% 1RM), CAFF 3mg did not improve SQ or BP muscle power or BP velocity. CAFF 9mg was needed to enhance BP velocity and SQ power at the heaviest load (90% 1RM) and cycling peak power output (6.8%-11.7%, P = 0.03-0.05). The CAFF 9mg trial drastically increased the frequency of the adverse side effects (15%-62%). The ergogenic dose of caffeine required to enhance neuromuscular performance during a single all-out contraction depends on the magnitude of load used. A dose of 3 mg · kg(-1) is enough to improve high-velocity muscle actions against low loads, whereas a higher caffeine dose (9 mg · kg(-1)) is necessary against high loads, despite the appearance of adverse side effects.