Effects of Caffeine Ingestion on Pulmonary V˙O2 Kinetics and Muscle Fatigue During Severe-Intensity Cycling Exercise.

Introduction: This study aimed to analyze the effect of caffeine (CAF) intake on pulmonary oxygen uptake (V˙O2) kinetics, muscle fatigue, and physiological and perceptual parameters during severe-intensity cycling exercise.
Methods: Twelve physically active men (age: 26 ± 5 years; V˙O2peak: 46.7 ± 7.8 ml·kg-1·min-1) participated of this placebo (PLA)-controlled, randomized, double-blinded, and crossover design study. Participants performed on separate days (a) a ramp incremental test to determine V˙O2peak and gas exchange threshold and (b) four 8-min constant work rate tests at 60% of the difference between gas exchange threshold and maximal V˙O2peak (i.e., Δ60%) 1 hr after taking either 6 mg/kg of body mass of CAF or PLA. Before and immediately after constant work rate tests, a 5-s all-out isokinetic sprint was performed to assess the muscle torque. V˙O2 kinetics, blood lactate concentration ([La]), and rating of perceived exertion were analyzed during constant work rate tests.
Results: CAF did not alter the primary time constant of V˙O2 kinetics (PLA: 38.3 ± 14; CAF: 36.7 ± 7.5 s), V˙O2 slow component (PLA: 0.5 ± 0.2; CAF: 0.5 ± 0.2 L/min), or peak torque (PLA: 144.6 ± 18.6; CAF: 143.9 ± 18.7 N·m). CAF decreased rating of perceived exertion (15.9 ± 1.8 vs. 17.0 ± 1.5 a.u.) and increased blood lactate concentration (9.0 ± 2.5 vs. 8.3 ± 2.2 mmol/L; p < .05) after constant work rate tests compared with PLA.
Conclusion: CAF ingestion does not alter V˙O2 kinetics or muscle torque production during 8 min of severe-intensity cycling exercise.