Hypoxic Respiratory Chemoreflex Control in Young Trained Swimmers.

Alexis Arce-Álvarez,Manuel Vazquez-Muñoz,Gregoire P Millet,Rodrigo Ramirez-Campillo,Rodrigo Del Rio,Mikel Izquierdo,David C Andrade,Magdalena Von Igel,Carlos Veliz,Cristian Alvares

doi:10.3389/fphys.2021.632603

Abstract

During an apnea, changes in PaO2 activate peripheral chemoreceptors to increase respiratory drive. Athletes with continuous apnea, such as breath-hold divers, have shown a decrease in hypoxic ventilatory response (HVR), which could explain the long apnea times; however, this has not been studied in swimmers. We hypothesize that the long periods of voluntary apnea in swimmers is related to a decreased HVR. Therefore, we sought to determine the HVR and cardiovascular adjustments during a maximum voluntary apnea in young-trained swimmers. In fifteen trained swimmers and twenty-seven controls we studied minute ventilation (VE), arterial saturation (SpO2), heart rate (HR), and autonomic response [through heart rate variability (HRV) analysis], during acute chemoreflex activation (five inhalations of pure N2) and maximum voluntary apnea test. In apnea tests, the maximum voluntary apnea time and the end-apnea HR were higher in swimmers than in controls (p < 0.05), as well as a higher low frequency component of HRV (p < 0.05), than controls. Swimmers showed lower HVR than controls (p < 0.01) without differences in cardiac hypoxic response (CHR). We conclude that swimmers had a reduced HVR response and greater maximal voluntary apnea duration, probably due to decreased HVR.

Highlights

Water sports are part of Olympic Games and have several modalities, including sailing, apnea dives, swimming, among others (FINA, 2020)
The maximum voluntary apnea duration was higher in swimmers than in control participants (83.18 ± 41.43 vs. 55.77 ± 23.71 s) (Figures 2A,B)
The heart rate (HR) response during the apnea was higher in swimmers compared to the controls (HR: 71.99 ± 7.67 vs. 63.20 ± 10.07 beats/min) (Figure 2C)

Summary

Introduction

Water sports are part of Olympic Games and have several modalities, including sailing, apnea dives, swimming, among others (FINA, 2020). Considering that PaO2 decreases and PaCO2 increases during apneas (Muth et al, 2003) and, that respiratory regions, at the brainstem level, could modulate the cardiovascular autonomic responses (Andrade et al, 2018; Díaz et al, 2020), the longer duration of apnea and cardiovascular adjustments to the apnea observed in swimmers, may be related to neural control of breathing, through a desensitization of peripheral chemoreceptors to hypoxia and hypercapnia. It has not been studied yet in swimmers. As swimmers are subjected to intermittent apneas during training session, it is possible that the apnea-dependent repetitive hypoxic-hypercapnic stimuli could induce a depressed respiratory neuroplasticity (Vermeulen et al, 2020) and impact on peripheral chemoreflex drive and possibly on apnea time

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