Caffeine has many diverse physiological effects including central nervous system stimulation. Ventilatory threshold and a recently described heart rate variability threshold both have a relationship with autonomic control that could be altered by caffeine consumption. The purpose of this investigation was to determine the influence of caffeine on lactate, ventilatory, and heart rate variability thresholds during progressive exercise. Using a randomized placebo controlled, double-blind study design, 10 adults performed 2 graded maximal cycle ergometry tests with and without caffeine (5 mg·kg⁻¹). Respiratory gas exchange, blood lactate concentrations, and heart rate variability data were obtained at baseline and throughout exercise. RESULTS: At rest, caffeine (p<0.05) increased blood lactate, oxygen consumption, carbon dioxide production, and minute ventilation. For indices of heart rate variability at rest, caffeine increased (p<0.05) the coefficient of variation, while standard deviation, and mean successive difference displayed non-significant increases. During progressive exercise, minute ventilation volumes were higher in caffeine trials but no other parameters were significantly different compared to placebo tests. CONCLUSION: These data demonstrate the robustness of the lactate, ventilatory and heart rate variability thresholds when challenged by a physiological dose of caffeine.

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