Three doses compared with a placebo
The researchers conducted a randomized, double-blind crossover trial: participants were studied under different conditions, with caffeine or a placebo. This method allows researchers to compare the same person’s responses under each condition tested.
The experimental doses were 3, 6 or 9 mg of caffeine per kilogram of body mass, given 70 minutes before a 17-minute CrossFit session. These amounts describe the experiment, not a recommended intake.
The study examined hematological and biochemical responses to this exercise, including blood cell indices, glucose and several minerals.
Glucose stands out from the other markers
The 6 and 9 mg/kg conditions produced greater increases in glucose after exercise than those observed with the placebo. The abstract reports a statistically significant difference but does not provide its absolute magnitude. Its practical importance therefore remains difficult to assess.
For blood cell indices, exercise was the main driver of change, with no caffeine-specific modulation detected. Changes in calcium depended on time rather than treatment, while magnesium remained stable.
Phosphate levels increased over time, particularly after exercise. However, the effect attributed to treatment was no longer supported in a sensitivity analysis excluding the initial visit. This finding therefore does not support a robust effect of caffeine on this marker.
A biological finding, not a verdict on performance
The central finding concerns blood glucose after a specific session. It demonstrates neither improved performance nor better recovery nor an adverse health outcome. A temporary rise in glucose is not enough to settle these questions.
The trial examined acute intake in a small group of moderately trained participants. It does not allow conclusions about repeated use, other populations or other training formats. The absence of changes in several blood markers does not establish the safety of the doses tested either.
Limitations to keep in mind
Only the PubMed abstract was reviewed, not the full text. The sample was limited to 26 participants, and exposure was acute. The abstract does not specify the absolute magnitude of the blood glucose differences, their uncertainty intervals or adverse effects. Funding and conflicts of interest were not checked.
What we can take away
In this trial, caffeine mainly affected glucose after CrossFit. This biological signal does not provide a demonstrated reason to increase your intake.
Sources and provenance
- Hematological and biochemical responses to three doses of caffeine during the CrossFit® workout: a randomized, double-blind, crossover trial.
Source date: 2026-10-23.
Journal Article, Randomized Controlled Trial · Résumé PubMed uniquement, texte intégral non consulté