Physiological Responses During Repeated Sprint Exercise With Voluntary Hypoventilation: Comparison With Hypoxic Condition

Abstract

Repeated sprint exercise in hypoxic condition is effective for improving repeated sprint ability. Moreover, repeated sprint exercise with voluntary hypoventilation at low lung volume (VHL) may be alternative procedures for establishing hypoxic environment in the body. Although the training with VHL caused further increase in repeated sprint ability compared with the same training with normal breath (Woorons et al., 2019), no direct comparison of the physiological responses to repeated sprint exercise between hypoxic condition and VHL was performed. PURPOSE: To compare the physiological responses during repeated sprint exercise using VHL with hypoxic condition. METHODS: Ten male subjects (21.8 ± 0.4 yrs, 168.6 ± 1.5 cm, 65.0 ± 2.2 kg) completed a single session of repeated sprint exercise (three sets of 6 × 8 s high intensity pedaling at 170% of VO2max) under 3 different conditions, (1) normoxia with normal breathing (NOR; 23 °C, FiO2 = 20.9%), (2) hypoxia with normal breathing (HYP; 23 °C, FiO2 = 14.5%), and (3) normoxia with VHL (VHL; 23 °C, FiO2 = 20.9%) with a single blind, randomized crossover design. Power output during each sprint, arterial oxygen saturation, heart rate, and muscle oxygenation were monitored during the exercise. We also measured muscle blood flow (mBF) and muscle oxygen consumption in vastus lateralis (muscle VO2) immediately after the exercise using venous/arterial occlusion and near infrared spectroscopy. RESULTS: Arterial oxygen saturation was significantly lower in VHL than in NOR. However, arterial oxygen saturation in VHL was significantly higher compared with HYP (NOR: 94.9 ± 0.4%, HYP: 82.8 ± 1.2%, VHL: 90.4 ± 0.5%, p < 0.05). Moreover, muscle oxygen saturation in HYP was significantly lower compared with both VHL and NOR (NOR: 80.1 ± 25.3%, HYP: 66.4 ± 21.0%, VHL: 75.2 ± 23.8%, p < 0.05), but there was no significant difference between VHL and NOR (p > 0.05). Also, mBF and muscle VO2 immediately after exercise did not differ significantly among conditions (p > 0.05). CONCLUSIONS: Although arterial oxygen saturation decreased during repeated sprint exercise with VHL, the exercise-induced decrement was smaller than hypoxic condition. Moreover, adding VHL during repeated sprint exercise did not elicit mBF and muscle VO2.