The randomised, double-blind, crossover study, published in the journal Nutrients, assessed the effect of supplementing with 5 mg/kg body weight caffeine over one week of training.
The authors from Spain found that the impact of caffeine intake improved the well-being, physical performance and perception of fatigue in the women's volleyball team athletes.
Female-focused research needed
Caffeine is often used in athletic performance as an ergogenic aid, with its popularity on the rise due to its effect on aerobic and anaerobic activities, increasing strength and power capacity by enhancing intracellular calcium and Na+-K+ ATPase pump activity and delaying the onset of fatigue through activation of the central nervous system, which blocks the adenosine receptors.
It has been well established that a range of supplementation with a dose of three to nine mg/kg body weight enhances athletic performance. And caffeine intake one hour before a training session has been shown to be an optimal strategy to enhance performance due to its fast absorption and plasma availability.
The authors noted that while previous volleyball studies have reported the effect of caffeine on jumping improvement, components such as agility and change of direction remain unclear and that more evidence is needed to determine the effect of caffeine on agility, especially in women’s volleyball.
“Caffeine has been proven to deliver positive outcomes in reducing perceived exertion and diminishing muscular soreness or damage, although to a lesser degree than in men," they wrote. “And, a main undesirable aspect to consider regarding caffeine supplementation in athletes is that it could negatively affect sleep quality, especially in women athletes because the effect of caffeine persists longer in women than in men.
“The scientific literature on the ergogenic effect of caffeine on women’s volleyball players is scarce or lacking, which highlights the importance of this topic in volleyball. Hence, it is important to know its effects on physical performance, fatigue, and wellness.”
The 'super league' study
The researchers recruited a sample of eight semi-professional women’s volleyball players from the “Spanish Women’s Superleague 2” between the ages of 17 and 25 years and assigned them to either a caffeine or placebo supplementation group. The caffeine group consumed 5 mg/kg of caffeine anhydrous powder based on body weight before acute training. Participants switched groups after a one-week washout period.
In both groups, participants performed countermovement jumps, repeated jumps and handgrip tests, and change of direction was assessed. Well-being was also evaluated by wellness questionnaire.
Results from ANOVA tests revealed a main effect of supplementation (F (1.7) = 8.41, p = 0.02, η2 = 0.54) across the training week on physical performance. The researchers also reported a significant effect of caffeine supplementation on perceived muscle damage and fatigue (F (1.7) = 7.29, p = 0.03, and η2 = 0.51), as well as better handgrip results in the caffeine group as compared to placebo but only in the dominant hand.
“Further similar research is needed in women that collects both physical performance and well-being parameters and correlates these variables, particularly in highly competitive periods such as the playoffs,” the researchers concluded.
“The Effect of Caffeine Supplementation on Female Volleyball Players’ Performance and Wellness during a Regular Training Week”
Authors: Jesús Siquier-Coll et al.