The effect of pre-exercise hyperventilation on repeated high-intensity inclined sprint performance

High-intensity exercise induces systemic acidosis, which contributes to muscular performance decline. Controlled pre-exercise hyperventilation has been proposed as a non-invasive intervention to induce respiratory alkalosis and counteract acidosis-related acute fatigue. In this study, we hypothesized that a real-world-applicable pre-exercise hyperventilation protocol can improve incline sprint performance. This randomized, single-centre, controlled crossover study included 36 recreational athletes aged 18-40 years. Each participant completed a series of three inclined treadmill interval sprints on two separate days: one with pre-exercise hyperventilation and one without. Respiratory parameters were measured via spirometry, and post-sprint capillary blood gas analysis was performed. Pre-exercise hyperventilation resulted in higher mean CO₂ elimination during hyperventilation (32.8 ± 5.1 vs. 21.5 ± 2.5 mL/kg, P < 0.0001) and lower mean end-tidal CO₂ partial pressure (17 ± 2.5 mmHg vs. 30 ± 2.7 mmHg, P < 0.0001) compared to control condition. Mean cumulative elevation gain did not differ between pre-exercise hyperventilation (83.2 ± 27.6 m) and control condition (84.3 ± 26.0 m, P = 0.6461). Differences in CO₂ elimination did not correlate with differences in performance (P = 0.5905). We found no alterations in post-sprint capillary blood lactate and pH between the two conditions (P > 0.05 for all sprints cumulatively and separately). Participants subjectively assessed the breathing protocol as unpleasant, and felt it negatively influenced their performance. The easily translatable pre-exercise hyperventilation protocol investigated in this study did not improve performance in repeated high-intensity incline sprint intervals. Therefore, we discourage its application in real-world applications.