Effect of Acute Hypoxia on Cardiorespiratory Coherence in Male Runners

Abstract

Understanding the mechanisms of oxygen supply regulation, which involves the respiratory and cardiovascular systems, during human adaptation to intense physical activity, accompanied by hypoxemia, is important for the management of a training process. The objectives of this study were to investigate the cardiorespiratory coherence (CRC) changes in the low-frequency band in response to hypoxic exposure and to verify a dependence of these changes upon sports qualification level in athletes. Twenty male runners aged 17-25 years were exposed to acute normobaric hypoxia (10% O 2) for 10 min. Respiration, gas exchange, and heart rate were measured at baseline, during hypoxia, and after the exposure. To evaluate cardiorespiratory coupling, squared coherence was calculated based on 5-s averaged time series of heart and respiratory rhythms. Based on sports qualification level achieved over 4 years after the experimental testing, athletes were retrospectively divided into two groups, one high level (HLG, n = 10) and the other middle level (MLG, n = 10). No differences in anthropometric traits were observed between the groups. In the pooled group, acute hypoxia significantly increased CRC at frequencies 0.030-0.045 Hz and 0.075 Hz. In response to hypoxia, oxygen consumption decreased in HLG, and carbon dioxide production and ventilation increased in MLG. At 0.070-0.080 Hz frequencies in hypoxia, the CRC in HLG was higher than in MLG. Thus, highly qualified athletes enhance intersystem integration in response to hypoxia. This finding can be a physiological sign for the prognosis of qualification level in runners.

Network Physiology of Exercise: Vision and Perspectives

“…The main findings of this set of studies point toward a higher sensitivity and responsiveness of cardiorespiratory coordination to exercise effects compared to isolated cardiorespiratory outcomes, such as VO 2max and other gold standard markers of aerobic fitness. More recent research has investigated changes on cardiorespiratory coherence in response to hypoxic exposure and verified its dependence upon fitness status (Uryumtsev et al, 2020). These results indicate that strengthening connectivity among physiological systems provides optimal responses to hypoxic exposure and reflects the adaptive adjustment of the cardiorespiratory system in trained individuals.…”

On the significance of estimating cardiorespiratory coupling strength in sports medicine

“…Squared coherence is usually averaged in specific frequency bands. Remarkably, both low frequency (LF, 0.04-0.15 Hz) and HF have been utilized in athletes according to the application: the LF band was utilized in hypoxic conditions in male runners (Uryumtsev et al, 2020), and the HF band in an The method does not account for directionality of interaction Distribution of time intervals between respiratory events and heartbeat Galletly and Larsen (1997) Amateur cyclists undergoing inspiratory muscle training and postural challenge Cairo et al (2020) The method considers only the heartbeat immediately preceding or following respiratory events, regardless of the rest of the heart rate variability series…”

“…Joint symbolic analysis Porta et al (2015) Amateur cyclists and non-athletes undergoing an orthostatic stressor Abreu et al (2022a) The method does not account for directionality of interaction Squared coherence Saul et al (1991) Amateur cyclists undergoing an orthostatic stressor de , and male runners in hypoxic conditions Uryumtsev et al (2020) The method does not account for temporal directionality and non-linear dynamics Granger causality Granger (1963), Porta and Faes (2016) Olympic athletes and non-athletes undergoing postural challenge Młyńczak and Krysztofiak (2019) The method does not account for non-linear dynamics…”

“…Moreover, this difference was identified only when non-linear approaches were applied to compute the CRC, such as joint symbolic analysis (Abreu et al, 2022a). In addition, an increase in CRC was detected during exposure to intense aerobic exercise under hypoxic situations (Uryumtsev et al, 2020). Conversely, a decrease in CRC strength was associated with situations evoking a high sympathetic tone (Iatsenko et al, 2013).…”

Cardiorespiratory Coordination in Hypercapnic Test Before and After High-Altitude Expedition

“…We have previously demonstrated that in swimming and skiing correlations between the responses of the cardiovascular and respiratory systems to acute hypoxic and hypercapnic tests are training-specific ( Divert et al, 2015 , 2017 ). Later we revealed that cardiorespiratory coherence changes in response to hypoxic exposure depend upon fitness status ( Uryumtsev et al, 2020 ). The study of cardiorespiratory interactions is in its initial stage, and the influencing CRC factors are to be investigated.…”