Hematological and biochemical responses to three doses of caffeine during the CrossFit® workout: a randomized, double-blind, crossover trial.
Natalia Główka, Tomasz Podgórski, Jakub Malik et al.
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In 30 seconds
This randomized, double-blind, placebo-controlled crossover trial examined hematological and biochemical responses to caffeine during a 17-minute CrossFit® workout in 26 moderately trained athletes. Participants received 3, 6, or 9 mg caffeine/kg body mass, or placebo, 70 minutes before exercise. Exercise was the main driver of hematological changes, with no caffeine-specific effects on blood cell indices. The clearest caffeine-related response was glucose: the 6 and 9 mg/kg doses produced significantly greater post-exercise elevations than baseline and placebo visits. Most other biochemical markers were not materially affected by caffeine.
Key findings
- The 6 and 9 mg caffeine/kg body mass doses produced significantly greater post-exercise glucose elevations than baseline and placebo visits.
- No caffeine-specific modulation of blood cell indices was observed; exercise was the predominant driver of hematological changes.
- Phosphate concentrations increased over time, particularly after exercise, but the treatment effect was not retained in sensitivity analysis excluding baseline.
- Calcium changes were associated with time rather than caffeine treatment, while magnesium remained stable.
Why it matters
The findings distinguish a selective glucose response from broader blood-cell or biochemical effects during this workout. They suggest that acute caffeine intake at the studied doses may alter post-exercise glucose patterns, while offering no evidence here of corresponding caffeine-related changes in hematological indices or most measured mineral markers.
What to keep in mind
The trial involved 26 moderately trained CrossFit® athletes and assessed responses to a single workout after acute caffeine dosing; the abstract does not report longer-term outcomes.