title: Acute effects of caffeine on strength and muscle activation of the elbow flexors.
abstract: The purpose of this study was to examine the effects of caffeine on strength and muscle activation of the elbow flexors. Thirteen recreationally active male volunteers (mean ± SD, age: 21.38 ± 1.26 years) came to the laboratory 4 times. Visit 1 served as a familiarization visit. During visits 2 through 4, subjects ingested a randomly assigned drink, with or without caffeine (0, 5, or 10 mg·kg of body mass), and performed 3 maximal isometric muscle actions of the elbow flexors 60 minutes after ingestion. Maximal strength and rate of torque development (RTD) were recorded. Electromyographic (EMG) and mechanomyographic (MMG) amplitude and frequency, and electromechanical delay (EMD), and phonomechanical delay (PMD) were measured from the biceps brachii. The results indicated that the ingestion of 0 (placebo), 5, or 10 mg·kg of body mass of caffeine did not significantly influence (p > 0.05) peak torque, RTD, normalized EMG amplitude or frequency, normalized MMG amplitude, or EMD and PMD. Normalized MMG frequency was significantly lower (p ≤ 0.05) following ingestion of 5 mg·kg of body mass of caffeine compared with the placebo trial. This was most likely an isolated finding because MMG frequency was the only variable to have a significant difference across all trials. The results suggested that ingestion of either 5 or 10 mg·kg of body mass of caffeine does not provide an ergogenic effect for the elbow flexors during isometric muscle actions.
authors.affiliation: 1Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas; 2Exercise Physiology Lab and Center for Sport Performance, Department of Kinesiology, California State University, Fullerton, Fullerton, California; and 3Department of Health Care Sciences, College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Trevino
authors.forename: Jared W
authors.initials: JW
authors.lastname: Coburn
authors.forename: Lee E
authors.initials: LE
authors.lastname: Brown
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Judelson
authors.forename: Moh H
authors.initials: MH
authors.lastname: Malek
mesh_terms: D000328:Adult; D002110:Caffeine / Q000008:administration & dosage*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004551:Elbow Joint / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000187:drug effects* / Q000502:physiology; D008297:Male; D053580:Muscle Strength / Q000187:drug effects* / Q000502:physiology; D011897:Random Allocation; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine