Effects of caffeine and its metabolites, theobromine and theophylline, on performance and physiological parameters in cyclists: A randomized, double-blind, placebo-controlled, crossover trial.

OBJECTIVE

This study aimed to evaluate the effects of caffeine and its metabolites, particularly theobromine and theophylline, on physiological and performance parameters in recreational cyclists.

METHODS

Fourteen male cyclists participated in a randomized, double-blind, crossover trial, completing a simulated 16 km time trial (TT) after ingesting 6 mg kg-1 of caffeine or a placebo. Physiological parameters such as ventilation (VE), heart rate (HR), and blood lactate were measured along with performance parameters like time and power output. Blood samples were collected to assess caffeine and metabolite concentrations before and after exercise.

RESULTS

The theophylline/caffeine ratio showed a significant correlation with VE (r = -0.69, p < 0.05) and TT duration (r = 0.73, p < 0.01). Similarly, the theobromine/caffeine ratio was significantly correlated with VE (r = -0.69, p < 0.05) and TT duration (r = 0.65, p < 0.01). Although elevated concentrations of theobromine and theophylline were associated with modulation of VE and prolonged TT duration, caffeine's ergogenic effect was maintained. This was evidenced by a significant increase in VE (Δ + 11.2 L min-1, p < 0.01) and blood lactate concentrations (Δ + 2.86 mmol L-1, p < 0.01). Caffeine ingestion also significantly improved TT time (Δ - 39.7 s, p < 0.01) and power output (Δ + 6.17 W, p < 0.01) compared to placebo.

CONCLUSIONS

These results suggest that although caffeine metabolites influence some physiological responses, the ergogenic benefits of caffeine remain robust, highlighting its role in enhancing performance in recreational cyclists.