Abstract
PurposeThis study investigated the effect of performing hypoxic exercise at the same heart rate (HR) or work rate (WR) as normoxic exercise on post-exercise autonomic and cardiovascular responses.MethodsThirteen men performed three interval-type exercise sessions (5 × 5-min; 1-min recovery): normoxic exercise at 80% of the WR at the first ventilatory threshold (N), hypoxic exercise (FiO2 = 14.2%) at the same WR as N (H-WR) and hypoxic exercise at the same HR as N (H-HR). Autonomic and cardiovascular assessments were conducted before and after exercise, both at rest and during active squat–stand manoeuvres (SS).ResultsCompared to N, H-WR elicited a higher HR response (≈ 83% vs ≈ 75%HRmax, p < 0.001) and H-HR a reduced exercise WR (− 21.1 ± 9.3%, p < 0.001). Cardiac parasympathetic indices were reduced 15 min after exercise and recovered within 60 min in N and H-HR, but not after H-WR (p < 0.05). H-WR altered cardiac baroreflex sensitivity (cBRS) both at rest and during SS (specifically in the control of blood pressure fall during standing phases) in the first 60 min after the exercise bout (p < 0.05). Post-exercise hypotension (PEH) did not occur in H-HR (p > 0.05) but lasted longer in H-WR than in N (p < 0.05).ConclusionsModerate HR-matched hypoxic exercise mimicked post-exercise autonomic responses of normoxic exercise without resulting in significant PEH. This may relate to the reduced WR and the limited associated mechanical/metabolic strain. Conversely, WR-matched hypoxic exercise impacted upon post-exercise autonomic and cardiovascular responses, delaying cardiac autonomic recovery, temporarily decreasing cBRS and evoking prolonged PEH.
Highlights
In the past few years, hypoxic exercise has been repeatedly highlighted as a promising nonpharmacological therapeutic intervention (Millet et al 2016; Millet and Girard 2017; Lizamore and Hamlin 2017; Brocherie and Millet 2020)
Work rate used during training sessions was 183 ± 19 W in N and H-work rate (WR) and 144 ± 18 W in H-heart rate (HR), with a mean decrement of − 21.1 ± 9.3% (p < 0.001)
Mean HR during exercise phases was significantly higher in H-WR (154 ± 11 bpm, 83 ± 5% HRmax) compared to N (139 ± 10 bpm; 75 ± 4% HRmax; p < 0.001) and H-HR (138 ± 9 bpm; 75 ± 4% HRmax; p < 0.001)
Summary
In the past few years, hypoxic exercise (i.e. exercise combined with hypoxic stress) has been repeatedly highlighted as a promising nonpharmacological therapeutic intervention (Millet et al 2016; Millet and Girard 2017; Lizamore and Hamlin 2017; Brocherie and Millet 2020). An exacerbated increase of exercise-induced physiological stress of hypoxic exercise can result in delayed recovery of autonomic balance (i.e. progressive restoration of normal resting balance between parasympathetic and sympathetic activity) and altered post-exercise cardiovascular responses (Romero et al 2017; Michael et al 2017). The timeframe for cBRS recovery depends on the physiological exercise intensity (Piepoli et al 1993; Halliwill et al 1996; Terziotti et al 2001; Raczak et al 2005; Reynolds et al 2017), which is higher at the same absolute WR in hypoxia Both the increased physiological exercise intensity relative to maximal, and hypoxic exercise per se, might negatively affect post-exercise cBRS responses, but this currently remains mere speculation. Studies investigating the impact of hypoxia on cBRS during exercise only compared similar absolute exercise intensities (same WR) (Bourdillon et al 2017, 2018)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
