Acute caffeine intake increases muscle oxygen saturation during a maximal incremental exercise test.

Abstract

Aims: The main mechanism behind caffeine’s ergogenicity lies in its tendency to bind to adenosine A1 and A2A receptors. However, other mechanisms might contribute to caffeine’s ergogenicity. The aim of this investigation was to analyze the effects of caffeine on muscle oxygen saturation during exercise of increasing intensity. Methods: Thirteen healthy and active individuals volunteered to participate in a randomized, double blind, placebo-controlled crossover trial. During two different trials, participants either ingested a placebo (cellulose) or 3 mg/kg of caffeine. After waiting for 60 min to absorb the substances, participants underwent a maximal ramp cycle ergometer test (25 W/min). Near infrared spectrometers were positioned on each leg’s vastus lateralis to monitor tissue O2 saturation. Blood lactate concentration was measured 1 min after the end of the exercise test. Results: In comparison to the placebo, the ingestion of caffeine improved the maximal wattage (258±50 vs 271±54 W, respectively, P < 0.001) and blood lactate concentration (11.9±3.8 vs 13.7±3.5 mmol/L, P = 0.029) at the end of the test. Caffeine increased muscle oxygen saturation at several exercise workloads with a main effect found in respect to the placebo (F = 6.28, P = 0.029). Peak pulmonary ventilation (124±29 vs 129±23 L/min, P=0.035) and VO2peak (3.18±0.70 vs 3.33±0.88 L/min, P=0.032) were also increased with caffeine. Conclusion: Acute ingestion of 3 mg/kg of caffeine improved peak aerobic performance while caffeine-induced changes seen in muscle oxygen saturation, pulmonary ventilation, and blood lactate accumulation suggest that these mechanisms might also contribute to caffeine’s ergogenic effect.