title: Neuromuscular responses to incremental caffeine doses: performance and side effects.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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%).
  
  
  CONCLUSIONS
  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.
authors.affiliation: 1Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Toledo, SPAIN; and 2Spanish Anti-doping Agency, Doping Control Laboratory in Madrid, SPAIN.
authors.forename: Jesús G
authors.initials: JG
authors.lastname: Pallarés
authors.forename: Valentín E
authors.initials: VE
authors.lastname: Fernández-Elías
authors.forename: Juan F
authors.initials: JF
authors.lastname: Ortega
authors.forename: Gloria
authors.initials: G
authors.lastname: Muñoz
authors.forename: Jesús
authors.initials: J
authors.lastname: Muñoz-Guerra
authors.forename: Ricardo
authors.initials: R
authors.lastname: Mora-Rodríguez
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology; D002110:Caffeine / Q000008:administration & dosage* / Q000009:adverse effects / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000378:metabolism; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005767:Gastrointestinal Diseases / Q000139:chemically induced; D006261:Headache / Q000139:chemically induced; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000502:physiology*; D063806:Myalgia / Q000139:chemically induced; D013610:Tachycardia / Q000139:chemically induced; D014556:Urine; D014891:Weight Lifting / Q000502:physiology; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine