Hypoxic Respiratory Chemoreflex Control in Young Trained Swimmers
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2021
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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 twentyseven
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.