Acute Effects of Caffeine on Strength and Muscle Activation of the Elbow Flexors

Abstract

PURPOSE: To examine the effects of caffeine on maximal strength, rate of torque development (RTD), electromyographic (EMG) and mechanomyographic (MMG) signals, and electromechanical (EMD) and phonomechanical (PMD) delay. METHODS: Fourteen male volunteers came to the laboratory four times. Visit one served as a familiarization visit. During visit two, subjects ingested a randomly assigned drink, either with or without caffeine (0, 5, or 10 mg·kg -1 of body mass), and performed three maximal isometric muscle actions of the elbow flexors sixty minutes after ingestion. Maximal strength and RTD were recorded. EMG and MMG amplitude and frequency, and EMD and PMD were measured from the biceps brachii. Visit three was identical to visit two, but one of the remaining two drinks not administered was assigned. Visit four followed the same procedures as visit three, but the one remaining drink not assigned was administered. RESULTS: There were no significant differences for maximal strength, RTD, EMG amplitude and frequency, MMG amplitude, EMD and PMD. MMG frequency was significantly lower after the ingestion of the 5 mg·kg -1 of body mass of caffeine drink compared to the placebo trial. This was most likely an isolated findinig as MMG frequency was the only variable to have a significant difference across all trials. CONCLUSIONS: The results suggested that ingestion of either 5 or 10 mg·kg -1 of body mass of caffeine does not provide ergogenic effects during isometric muscle actions of the elbow flexors.