The Claim

In trained adolescent male volleyball players, acute ingestion of 3 mg/kg of caffeine via capsule or mouth rinse improves vertical jump height and change-of-direction speed, with the greatest benefits occurring in the morning and midday when baseline performance is lower, and this effect partially attenuates circadian-related performance decrements in explosive power and agility.

Source: Differential Time-of-Day Effects of Caffeine Capsule and Mouth Rinse on Physical Performance and Volleyball-Specific Skills in Adolescent Male Volleyball Players

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
70score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Cause and effect
1 study reviewed
In plain English

In trained adolescent male volleyball players, taking 3 mg/kg of caffeine before exercise increases vertical jump height and change-of-direction speed more in the morning and midday than in the evening, due to reduced circadian-related declines in explosive power and agility.

See the scientific wording

In trained adolescent male volleyball players, acute ingestion of 3 mg/kg of caffeine via capsule or mouth rinse improves vertical jump height and change-of-direction speed, with the greatest benefits occurring in the morning and midday when baseline performance is lower, suggesting caffeine partially attenuates circadian-related performance decrements in explosive power and agility.

Why this might work

Caffeine blocks natural brain chemicals that slow down nerve signals, making the brain more alert and forcing muscles to contract faster and harder, which makes jumping higher and changing direction quicker, especially when the body is naturally slower in the morning or afternoon.

Verified mechanismbased on 1 study

What the research says

1 study

  1. Study: Differential Time-of-Day Effects of Caffeine Capsule and Mouth Rinse on Physical Performance and Volleyball-Specific Skills in Adolescent Male Volleyball Players

    When teen volleyball players took caffeine either as a pill or by swishing it in their mouth, they jumped higher and moved faster in the morning and afternoon than at night—because their bodies naturally perform worse then, and caffeine helped make up for that. It’s like a boost that works best when you’re feeling sluggish.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

Fit Body Science verdict — we translate health claims into clear verdicts backed by peer-reviewed research.

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