Hematological and biochemical responses to three doses of caffeine during the CrossFit® workout: a randomized, double-blind, crossover trial.
4 affiliations
- 1Poznan University of Physical Education, Department of Sports Dietetics, Poznań, Poland.
- 2Poznan University of Physical Education, Department of Biochemistry, Poznań, Poland.
- 3Poznan University of Physical Education, Department of Sports Psychology, Poznań, Poland.
- 4Polish Society of Nutritional Sciences, Warsaw, Poland.
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.
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BibTeX
@article{glowka2026hematological,
title = {{Hematological and biochemical responses to three doses of caffeine during the CrossFit® workout: a randomized, double-blind, crossover trial.}},
author = {Natalia Główka and Tomasz Podgórski and Jakub Malik and Paulina M Nowaczyk and Krzysztof Durkalec-Michalski},
journal = {Journal of the International Society of Sports Nutrition},
year = {2026},
month = oct,
doi = {10.1080/15502783.2026.2740805},
url = {https://europepmc.org/article/MED/42924484},
note = {CC BY},
}
RIS
TY - JOUR
TI - Hematological and biochemical responses to three doses of caffeine during the CrossFit® workout: a randomized, double-blind, crossover trial.
AU - Natalia Główka
AU - Tomasz Podgórski
AU - Jakub Malik
AU - Paulina M Nowaczyk
AU - Krzysztof Durkalec-Michalski
PY - 2026
DA - 2026/10/23
JO - Journal of the International Society of Sports Nutrition
DO - 10.1080/15502783.2026.2740805
UR - https://europepmc.org/article/MED/42924484
AB - 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.
SN - 1550-2783
ER -