Journal of the International Society of Sports Nutrition
Hematological and biochemical responses to three doses of caffeine during the CrossFit® workout: a randomized, double-blind, crossover trial
By Główka N, Podgórski T, Malik J and 2 others.
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.