Abstract
This study investigated the impact of hyperoxic gas breathing (HYP) on repeated-sprint ability (RSA) and on the associated training load (TL). Thirteen team- and racquet-sport athletes performed 6-s all-out sprints with 24-s recovery until exhaustion (power decrement ≥ 15% for two consecutive sprints) under normoxic (NOR: FIO2 0.21) and hyperoxic (HYP: FIO2 0.40) conditions in a randomized, single-blind and crossover design. The following variables were recorded throughout the tests: mechanical indices, arterial O2 saturation (SpO2), oxygenation of the vastus lateralis muscle with near-infrared spectroscopy, and electromyographic activity of the vastus lateralis, rectus femoris, and gastrocnemius lateralis muscles. Session TL (work × rate of perceived exertion) and neuromuscular efficiency (work/EMG [Electromyography]) were calculated. Compared with NOR, HYP increased SpO2 (2.7 ± 0.8%, Cohen's effect size ES 0.55), the number of sprints (14.5 ± 8.6%, ES 0.28), the total mechanical work (13.6 ± 6.8%, ES 0.30), and the session TL (19.4 ± 7.0%, ES 0.33). Concomitantly, HYP increased the amplitude of muscle oxygenation changes during sprints (25.2 ± 11.7%, ES 0.36) and recovery periods (26.1 ± 11.4%, ES 0.37), as well as muscle recruitment (9.9 ± 12.1%, ES 0.74), and neuromuscular efficiency (6.9 ± 9.0%, ES 0.24). It was concluded that breathing a hyperoxic mixture enriched to 40% O2 improves the total work performed and the associated training load during an open-loop RSA session in trained athletes. This ergogenic impact may be mediated by metabolic and neuromuscular alterations.
Highlights
The nature and the magnitude of a training effect are dictated by the frequency, duration, and intensity of the exercise; the so-called training load (TL)
The peak power output (PPO) reached was similar in both conditions, but hyperoxic gas breathing (HYP) extended the number of sprints performed before exhaustion compared to NOR
The total work performed over the entire series increased in HYP (13.6 ± 6.8%, effect size (ES) 0.30), but when the same number of sprints was considered in both NOR and HYP, the work in these common sprints did not change meaningfully (2.0 ± 1.7%, ES 0.05)
Summary
The nature and the magnitude of a training effect are dictated by the frequency, duration, and intensity of the exercise; the so-called training load (TL). Performance during aerobic exercise such as time trials, time to exhaustion, graded exercise tests, and dynamic muscle function tests is, not surprisingly, acutely improved under hyperoxic conditions (Peltonen et al, 2001; Tucker et al, 2007; Manselin et al, 2017) Those improvements are mainly derived from the increase in arterial hemoglobin saturation (SaO2), arterial content of oxygen (CaO2), and the systemic O2 delivery to organs and skeletal muscles (Powers et al, 1993; Peltonen et al, 1995). Higher peak and mean power output have been documented when breathing 100% O2, compared to room air, during two 30-s cycle sprints separated by 4 min (Kay et al, 2008), during five sets of 40 high-intensity breast strokes (∼50 s) (Sperlich et al, 2011), and during ten 15-s cycling sprints interspersed with 45 s of recovery (Porter et al, 2020) Overall, these data indicate that hyperoxia may be beneficial to exercise performance in varied sport settings, the activity patterns of intermittent sports such as rackets and team sports have received limited attention so far
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