J Int Soc Sports Nutr. 2026 Dec 30;23(1):2740805. doi: 10.1080/15502783.2026.2740805. Epub 2026 Oct 23.
ABSTRACT
BACKGROUND: This study investigated the effects of three doses of caffeine (CAF) on hematological and biochemical responses during the CrossFit® workout, a protocol known to induce significant physiological fluctuations.
METHODS: In a randomized, double-blind, placebo (PLA)-controlled crossover trial, 26 moderately trained CrossFit® athletes received acute doses of 3, 6, or 9 mgCAF/kgbody mass (BM), or a PLA, 70 min before a 17-min CrossFit® workout.
RESULTS: While exercise was the predominant driver of hematological changes, with no CAF-specific modulation of blood cell indices, significant treatment × time point interactions were observed solely for glucose concentration. Specifically, MEDIUM (6 mgCAF/kgBM) and HIGH (9 mgCAF/kgBM) CAF doses produced significantly greater post-exercise glucose elevations compared to baseline and PLA visits. Phosphates concentrations increased over time, particularly post-exercise, with no treatment effect retained after excluding baseline visit in the sensitivity analysis. Calcium level dynamics were influenced by temporal factors rather than CAF, and magnesium concentration remained stable.
CONCLUSIONS: These findings suggest that acute CAF ingestion selectively influences post-exercise glucose responses during the CrossFit® workout, whereas hematological variables and most biochemical markers remain unaffected. Significant post-exercise glucose elevations were observed following the 6 and 9 mgCAF/kgBM conditions compared with baseline and PLA visits, while serum mineral concentrations remained largely stable across treatments.
CLINICAL TRIALS REGISTRATION: NCT03822663.
PMID:42924484 | DOI:10.1080/15502783.2026.2740805
