The effect of severe and moderate hypoxia on exercise at a fixed level of perceived exertion

Owen Jeffries,Mark Waldron,Stephen David Patterson

doi:10.1007/s00421-019-04111-y

Owen Jeffries, Mark Waldron + Show 1 more

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https://doi.org/10.1007/s00421-019-04111-y

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Abstract

PurposeThe purpose of this study was to determine the primary cues regulating perceived effort and exercise performance using a fixed-RPE protocol in severe and moderate hypoxia.MethodsEight male participants (26 ± 6 years, 76.3 ± 8.6 kg, 178.5 ± 3.6 cm, 51.4 ± 8.0 mL kg− 1 min− 1dot {V}O2max) completed three exercise trials in environmental conditions of severe hypoxia (FIO2 0.114), moderate hypoxia (FIO2 0.152), and normoxia (FIO2 0.202). They were instructed to continually adjust their power output to maintain a perceived effort (RPE) of 16, exercising until power output declined to 80% of the peak 30-s power output achieved.ResultsExercise time was reduced (severe hypoxia 428 ± 210 s; moderate hypoxia 1044 ± 384 s; normoxia 1550 ± 590 s) according to a reduction in FIO2 (P < 0.05). The rate of oxygen desaturation during the first 3 min of exercise was accelerated in severe hypoxia (− 5.3 ± 2.8% min− 1) relative to moderate hypoxia (− 2.5 ± 1.0% min− 1) and normoxia (− 0.7 ± 0.3% min− 1). Muscle tissue oxygenation did not differ between conditions (P > 0.05). Minute ventilation increased at a faster rate according to a decrease in FIO2 (severe hypoxia 27.6 ± 6.6; moderate hypoxia 21.8 ± 3.9; normoxia 17.3 ± 3.9 L min− 1). Moderate-to-strong correlations were identified between breathing frequency (r = − 0.718, P < 0.001), blood oxygen saturation (r = 0.611, P = 0.002), and exercise performance.ConclusionsThe primary cues for determining perceived effort relate to progressive arterial hypoxemia and increases in ventilation.

Highlights

Exercise performance during an acute exposure to hypoxia is impaired via a reduction in arterial oxygen content (Fulco et al 1996, 1998; Calbet et al 2003a; Amann et al 2006b; Romer et al 2006)
The achieved power output associated with an Rating of perceived exertion (RPE) of 16 was different between conditions (F(1.180,8.262) = 9.558, P = 0.012, ηp2 = 0.577) (Table 1), with pairwise analysis, confirming that the power output achieved in severe hypoxia was reduced relative to moderate hypoxia and normoxia
The rate of decrease in power output did not differ between conditions once peak power was achieved; the early setting of an acceptable perceived exercise intensity appears crucial to exercise performance

Summary

Introduction

Exercise performance during an acute exposure to hypoxia is impaired via a reduction in arterial oxygen content (Fulco et al 1996, 1998; Calbet et al 2003a; Amann et al 2006b; Romer et al 2006). In moderate hypoxia, where the oxygen fraction of inspired air is reduced to ~ 13–15% (FIO2 0.13–0.15), decrements in performance have been attributed to a rise in peripheral markers of muscle fatigue, which generate afferent feedback to down-regulate motor output from the central nervous system (CNS) (Amann et al 2006b, 2007; Romer et al 2007). In severe hypoxia (FIO2 < 0.115), larger reductions in exercise capacity have been described despite relatively less evidence of peripheral fatigue (Amann et al 2007). In experiments where FIO2 is increased at the point of task failure, exercise performance can be prolonged in severe and moderate hypoxia (Amann et al 2007; Torres-Peralta et al 2016)

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