Dose-specific effects of caffeinated chewing gum on reactive blocking timing, jump mechanics, and neuromuscular responses after volleyball-specific fatigue in elite female volleyball players.
Jinghui Zhong, Jiyan Xu, Chang Lu et al.
✦ AI-curated · Sources linked
In 30 seconds
This randomized, double-blind, placebo-controlled crossover study examined caffeinated chewing gum in 15 elite female volleyball players after a volleyball-specific repeated-blocking fatigue protocol. Compared with placebo, the 6 mg/kg target dose showed a smaller descriptive decline in block-jump peak power (6.9% vs 13.9%) and the smallest increase in overall reactive blocking sequence time (3.0% vs 18.4%). However, adjusted post-fatigue comparisons did not establish superiority of 6 mg/kg over 3 mg/kg, and responses varied by outcome. Incomplete participant masking limits attribution of observed differences exclusively to caffeine dose.
Key findings
- Block-jump peak power declined descriptively by 6.9% with CAF6 versus 13.9% with placebo; adjusted comparisons did not establish CAF6 superiority over CAF3.
- Overall sequence time increased by 3.0% with CAF6, 6.4% with CAF3, and 18.4% with placebo.
- Selected countermovement- and drop-jump measures favored caffeine after fatigue; CAF6 better preserved drop-jump height and vertical stiffness than placebo.
- Participants reported perceived caffeine ingestion in 0.0% of placebo, 53.3% of CAF3, and 80.0% of CAF6 visits; adverse effects were more frequent with CAF6.
Why it matters
Fatigue can impair jump performance and reactive blocking, both relevant to volleyball performance. These findings suggest that caffeine gum may have outcome-specific effects after volleyball-specific fatigue, but they do not identify a generally preferable dose or establish that observed differences were caused solely by caffeine. The results also highlight the importance of considering masking and adverse effects when interpreting supplementation studies.
What to keep in mind
The study included 15 players, participant masking was incomplete, and adverse effects were more frequent with CAF6. The reported dose comparisons did not establish CAF6 superiority over CAF3.