Acute effect of caffeine consumption on isotonic muscular strength and endurance: A systematic review and meta-analysis

    M.D. Polito, , , D.B. Souza, J. Casonatto, P. Farinatti

a Physical education department, Londrina state university, Rod. Celso Garcia Cid, km 380, 86050-520 Londrina, PR, Brazil
b Center of life sciences and health, university of North Paraná, Londrina, Brazil
c Laboratory of physical activity and health promotion, Rio de Janeiro State university, Rio de Janeiro, Brazil

Science & Sports journal

Objectives
The aim of the present study was to perform a systematic review and meta-analysis of the acute effects of caffeine ingestion on maximal strength and muscular endurance in isotonic resistance exercises.
Equipment and methods

Up until March 2015, 17 studies which met the inclusion criteria, 42 trials related to muscular endurance and 5 trials related to muscular strength, were found from a search in the following databases: PubMed, ISI Web of Knowledge, SportDiscus, Scielo, Lilacs, Medcarib, Ibecs and ProQuest Dissertations & Theses. The effect sizes were calculated as the standardized mean difference and meta-analysis were completed using a random-effects model.

Results
No significant effects were identified for gender, muscle location, muscle size, dosage of caffeine or form or timing of pre-exercise caffeine consumption on performance at maximum strength. For muscular endurance, all moderators were related to improve performance after caffeine intake (P < 0.01). The between groups analysis showed no differences with regard to the effect sizes in the comparisons for muscle location (P = 0.09); muscle size (P = 0.12); caffeine dosage (P = 0.08); and form of intake (P = 0.24). Effect size related to time of consumption pre-exercise was significant only for 60 min, with significant differences vs. 45 min and 90 min (P = 0.04). Comparisons between gender groups were not possible, since only one trial investigated females.

Keywords
Nutrition; Resistance training; Central nervous system; Stimulants; Data analyses

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