Dose-Dependent Effects of Acute Caffeine Ingestion on Physical and Cognitive Performance in Female Handball Players: A Randomized, Double-Blind, Placebo-Controlled Crossover Study

Caffeine is one of the most widely consumed ergogenic aids in sport, known to influence both physiological and cognitive processes primarily through antagonism of adenosine receptors. Although its beneficial effects on endurance performance and alertness are well established, evidence regarding its effects on cognitive control and sport-specific technical skills remains inconsistent, particularly in team sport settings where multiple performance domains interact.

Team sports such as handball require the integration of intermittent high-intensity physical efforts, rapid decision-making, and precise motor execution. These components are not independent; instead, they compete for shared neurocognitive resources, especially under conditions of fatigue. As a result, interventions such as caffeine supplementation may exert domain-specific effects rather than uniform improvements across all aspects of performance.

Despite extensive research on caffeine, most studies have examined either physical or cognitive outcomes in isolation. Furthermore, dose-response relationships remain unclear, with previous findings suggesting that lower doses may be sufficient to enhance physical performance, whereas cognitive outcomes may require higher levels of stimulation. However, limited evidence exists on whether these dose-dependent effects are maintained when multiple performance domains are assessed within the same experimental framework.

The present study addresses this gap by simultaneously evaluating physical, cognitive, and sport-specific motor performance following different doses of caffeine in female handball players. A randomized, double-blind, placebo-controlled crossover design is used to minimize inter-individual variability and improve internal validity. Participants complete three experimental conditions (placebo, low-dose caffeine, and moderate-dose caffeine), each separated by an adequate washout period to reduce potential carryover effects.

The protocol includes standardized procedures to control for confounding factors such as time of day, environmental conditions, and prior physical activity. Testing sessions follow a fixed sequence, beginning with cognitive assessment, followed by a sport-specific throwing task, and concluding with an intermittent running test. This structure is designed to reflect the multi-component demands of team sport performance while maintaining methodological control.

The primary objective is to determine whether caffeine produces dose-dependent effects across different performance domains. Specifically, the study examines whether physical performance improvements occur at lower doses, whether cognitive performance shows greater sensitivity to higher doses, and whether technical motor performance responds differently to caffeine ingestion. By integrating these domains within a single experimental design, the study aims to provide a more ecologically valid understanding of caffeine's ergogenic effects in team sport contexts.

The findings are expected to contribute to evidence-based recommendations for caffeine use in athletes, emphasizing the importance of aligning supplementation strategies with specific performance goals rather than assuming uniform benefits across all domains.