Ergogenic Effects of Acute Caffeine Intake on Muscular Endurance and Muscular Strength in Women: A Meta-Analysis
Grgic J, Del Coso J. Int J Environ Res Public Health. 2021 May 27;18(11):5773. doi: 10.3390/ijerph18115773
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Caffeine supplements before exercise may improve muscular performance in women.
Caffeine is a common ergogenic supplement for athletes. Researchers have found that caffeine supplementation can be used to enhance exercise performance and endurance. However, much of this work was conducted among males.
The authors conducted a meta-analysis to explore the effects of caffeine ingestion on muscle endurance and muscular performance in females.
The authors conducted a systematic literature search and identified 1,214 articles before screening for the following criteria: (1) published in English, (2) included women as study participants, (3) utilized a single or double-blind placebo-controlled crossover design, and (4) evaluated the effects of isolated caffeine ingestion on 1-repetition-maximum (RM) strength or muscular endurance in an isotonic test. Eight studies met the inclusion criteria. The authors assessed study quality for each study using the PEDro checklist.
Sample sizes of the included studies ranged from 8 to 29 female participants. All the studies evaluated the effects of caffeine on muscular endurance, while 6 studies also examined the effects of caffeine on 1-RM strength (bench, squat). One study used 2 absolute doses of 100mg and 400mg 60 minutes before exercise. Seven of the studies assessed caffeine supplementation (2-6 mg/kg) 60-minutes pre-exercise, and one study investigated 6 mg/kg caffeine ingestion 30 minutes pre-exercise. Overall, caffeine supplementation before exercise had a small effect on enhancing muscle endurance and strength. These improvements for muscle endurance and strength were found in upper body exercises (5 studies), but not lower body exercises (4 studies).
Ultimately, the authors determined that caffeine ingestion has a significant yet small effect on muscle endurance and performance in females. However, the ergogenic effect of caffeine on muscle endurance and strength was primarily found in upper body exercise. Therefore, if a female wants to enhance lower body strength and endurance, it is unclear if caffeine will help. While the caffeine supplementation protocols were similar (2-6 mg/kg caffeine ingestion from 30-60 min pre-exercise), the muscle endurance and performance protocols were variable (sets, reps, %RM). Future research is needed to establish optimal caffeine dosage and timing to optimize positive outcomes.
Medical professionals can inform females interested in the acute enhancement of muscles endurance and strength that caffeine ingestion pre-exercise may be beneficial.
Questions for Discussion
Do you use caffeine as an ergonomic agent to enhance muscular performance? If so, have you seen improvements in upper or lower extremity exercises?
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Written by: Jane McDevitt
Reviewed by: Jeffrey Driban