Ergogenic Effects of Acute Caffeine Intake on Muscular Endurance and Muscular Strength in Women: A Meta-Analysis

Abstract

This meta-analysis aimed to explore the effects of caffeine ingestion on muscular endurance and muscular strength in women. Five databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed for data analysis. Subgroup meta-analyses explored the effects of caffeine on upper-body and lower-body muscular endurance and muscular strength. Eight crossover placebo-controlled studies were included in the review. In the main meta-analysis that considered data from all included studies, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.25; p = 0.027) and muscular strength (SMD = 0.18; p < 0.001). In a subgroup analysis that considered only upper-body exercises, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.20; p = 0.007) and muscular strength (SMD = 0.17; p < 0.001). In a subgroup analysis that considered only lower-body exercises, there was no significant difference between caffeine and placebo for muscular endurance (SMD = 0.43; p = 0.092) or muscular strength (SMD = 0.16; p = 0.109). The main finding of this meta-analysis is that caffeine ingestion has a significant ergogenic effect on muscular endurance and muscular strength in women. The effects reported in this analysis are similar to those previously observed in men and suggest that women may use caffeine supplementation as an ergogenic aid for muscular performance. Future research is needed to explore the effects of caffeine on lower-body muscular endurance and muscular strength in this population.

The Effects of Caffeine on Jumping Performance and Maximal Strength in Female Collegiate Athletes

“…Thus, with a sample size of 11 athletes, it is possible our study was underpowered. Nonetheless, our results agree with the meta-analyses by Grgic et al [ 17 ] and Grgic and Del Coso [ 28 ] showing no effect of caffeine on lower-body maximal strength.…”

“…Considering caffeine may have larger ergogenic effects on trained muscle [ 15 , 22 , 44 ], this could partly explain the discrepancy between Ali et al [ 18 ] and Arazi et al [ 27 ] in caffeine’s effects on strength performance. Meta-analytic results suggest caffeine’s effect on maximal strength performance is small (effect size ~0.20) compared to a placebo [ 17 , 28 ]. Thus, with a sample size of 11 athletes, it is possible our study was underpowered.…”

“…These findings were later confirmed by Temple et al [ 20 ], furthering the need for additional examinations of females’ physiological response to caffeine. Furthermore, a review by Grgic and Del Coso [ 28 ] concluded that the assessment of lower body strength with females implementing caffeine supplementation is warranted due to the equivocal findings in the literature thus far. Due to these limitations, further research is needed assessing the effects of caffeine on multi-joint, lower body strength and power in female athletes.…”

Effects of carbohydrate and caffeine mouth rinsing on strength, muscular endurance and cognitive performance

“…CAF binds to adenosine receptors A 1 and A 2 , reducing the influence of the parasympathetic system and increasing the synthesis of neurotransmitters such as dopamine and catecholamines, increasing cognitive performance [ 4 ], tension, vigor and perception of vitality and a reduction between training load and ratings of perceived exertion (RPE) on elite and moderately trained athletes [ 5 ]. At the peripheral level, CAF improves sodium-potassium (Na + -K + ) pump activity and increases the bioavailability of calcium (Ca 2+ ) in the myoplasm [ 6 ]; mechanisms that explain an enhancement of one repetition maximum (1-RM) [ 7 ] power output with a determined load [ 8 ] and muscular endurance [ 9 ] in resistance exercises. A line of emerging enquiry, “mouth rinsing” without swallowing, developed two decades ago, suggests that CHO and/or CAF mouth rinsing may increase aerobic endurance-sprint type activities and cognitive performance via central mechanisms [ 10 – 12 ].…”

The Dose-Effects of Caffeine on Lower Body Maximal Strength, Muscular Endurance, and Rating of Perceived Exertion in Strength-Trained Females

“…Fewer investigations, compared to endurance exercise, have examined caffeine's effect on resistance exercise, including maximal muscular strength and muscular endurance [18]. Whilst a meta-analysis has stated that caffeine can improve muscular strength and muscular endurance [19], there are still questions and conflict between the effects on gender [17], muscle group (upper vs. lower) and strength qualities [20]. These concerns are exemplified when investigating the effects of caffeine on strength components for female participants/athletes, with Grgic and Del Coso's [20] recent meta-analysis concluding that future research is required to investigate the effects of caffeine on lower-body muscular endurance and muscular strength.…”