Causes of bradycardia with static respiratory hypoxia in athletes

According to some literature data, during voluntary long-term breath holding (BH), the heart rate (HR) increases, and according to others, it decreases.

Objective: to determine the psychophysiological parameters that cause a change in HR during BH in athletes with different resistance to respiratory hypoxia.

Materials and methods: HR at BH was studied in 14 beginner athletes, 15 basketball players and 12 swimmers-divers. Duration of BH was recorded. The HR was recorded on a heart rate monitor. After recording an electrocardiogram, the standard deviation of the duration of cardiac cycles was calculated. The arterial oxygen saturation was measured with a pulse oximeter. The statistically significant values of the correlation coefficient (r) were ≥0.33 with p < 0.05.

Results: it was found that out of 41 sportsmen, HR increased by more than 5 % in 4, changed insignificantly in 7 and decreased by less than 5 % in 30. Beginner athletes had tachycardia, and BH was quickly interrupted by an imperative inhalation. The saturation of arterial blood with oxygen did not change and did not affect the change in HR. The decrease in heart rate in swimmers-divers in comparison with the other two groups of people examined was statistically significant (p < 0.05). The duration of BH had a direct correlation (r = 0.5) with bradycardia in these people. The duration of BH caused (r = 0.8) hypoxia, the value of which also directly influenced (r = 0.38) the severity of bradycardia. In addition, the decrease in HR depended on high HR (r = 0.36) and low HR variability (r = 0.38) before BH.

Conclusion: tachycardia occurs in beginner athletes who experience discomfort with BH. Bradycardia occurs in sportsmen with a long-term BH setting without discomfort. Sympathicotonia in the prelaunch state predetermines the severity of bradycardia in BH. The duration of BH and the resulting hypoxia provide the occurrence of bradycardia.

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