The randomized, placebo controlled crossover trial, published in the Journal of the International Society of Sports Nutrition, found no dose-dependent effect of caffeine supplementation in moderately trained CrossFit/HIFT participants on a range of performance markers.
However, the researchers did note that the medium dose of caffeine (6 mg CAF/kg BM) induced clinically noticeable improvements in exercise repetitions, pre-exercise motor time and reaction time, suggesting that this dose may be the most effective for CrossFit/HIFT practitioners from the clinical and athletic point of view.
Caffeine and exercise performance
CAF ingestion promotes muscle endurance and strength, along with the enhancement of anaerobic and aerobic stamina. The specific CAF dose for optimal physical strength or exercising ability may differ based on several factors, such as gender, exercise type or CAF consumption habits.
Several underlying mechanisms through which CAF enhances exercise performance have been proposed. For instance, CAF binds with adenosine receptors of the central nervous system (CNS) or augments the availability of energy substrate and myofibrillar calcium that is responsible for ergogenic effects.
CrossFit is a High-Intensity Functional Training (HIFT) that improves exercise performance, aerobic and anaerobic capacity, resting heart rate (HR), strength and overall physical fitness. For an athlete, concentration and reaction are crucial cognitive functions that govern their performance. CAF can induce the release of neurotransmitters that enhance cognitive function, reduce fatigue and increase alertness. Taken together, CAF can improve the overall performance of athletes.
Dose-dependent effect on CrossFit performance
A total of 26 (10 females and 16 males) moderately trained CrossFit practitioners were recruited to assess the impact of three different CAF doses, i.e., 3 (low), 6 (medium) and 9 (high) mg/kg body mass (BM) compared to placebo (PLA) on performance, postural stability (PStab), reaction time (RTime), heart rate (HR) and perceived exertion (RPE).
The athletes were evaluated on the basis of five different testing sessions using the Fight Gone Bad test (FGB). On testing days, participants received either CAF supplements or PLA 70 minutes before the test sessions. Each test session included five exercises: wall ball shots, sumo deadlift high pulls, box jumps, push presses and rowing.
It was hypothesized that the effect of CAF doses varies based on single nucleotide polymorphism (SNP) in the CYP1A2 (rs762551) and ADORA2A (rs5751876) genes. However, experimental findings did not support this hypothesis. No significant differences in CrossFit performance, PStab, RTime, RPE, HR and pyruvate concentrations were noted across different CAF doses and PLA.
However, supplementation with a medium CAF dose (6 mg CAF/kg BM) showed the greatest effectiveness in terms of the total number of exercise repetitions, pre-exercise motor time and reaction time.
The highest blood lactose concentration was achieved post-exercise at a high CAF dose. Mechanistically, this increase could be adrenaline-mediated. Adrenalin augments the capacity to perform HIFT for longer durations, which causes greater lactate accumulation.
Journal: Journal of the International Society of Sports Nutrition
“The dose-dependent effect of caffeine supplementation on performance, reaction time and postural stability in CrossFit – a randomized placebo-controlled crossover trial.”
doi: 10.1080/15502783.2023.2301384
Authors: Natalia Główka et al.