Cardiac and ventilatory responses to apneic exercise

Abstract

This study was to elucidate the physiological effects of dynamic apneas, as performed as a discipline in breath-hold diving for recreational or competitive purposes. Therefore, cardiovascular and respiratory effects of apneas with simultaneously initiated exercise were investigated in ten trained breath-hold divers. They performed maximum duration apneas with face immersion (26 degrees C) under rest and exercise (40 W, 80 W and 120 W) on a cycle ergometer in the laboratory. Apneic time, heart rate (HR), mean arterial pressure (MAP), arterial oxygen saturation and O2 (.VO2) and CO2 exchange were measured. All end-apnea heart rates were lower than corresponding control values. Higher workloads increased the initial rise in HR and delayed the onset of bradycardia. After an initial drop, MAP rose to 150% of control towards the end of apnea. Apneic .VO2 was reduced by 25% during exercise and by 40% during resting apneas compared to eupneic control values. It was concluded that magnitude and time course of diving bradycardia depend on work intensity. Higher workloads delay the onset and attenuate HR reduction, presumably due to increased sympathetic activity. It was also found that apnea with simultaneously initiated exercise has an O2 conserving effect compared to eupneic exercise. Although aimed to be a realistic approach to breath-hold diving, the study has certain methodological limitations in terms of body-immersion (hydrostatic pressure effects) and body-cooling effects due to conduction of the experiments in a laboratory set-up.

Physiological Responses in Relation to Performance during Competition in Elite Synchronized Swimmers

“…The observed periods of bradycardia in our swimmers, who reached minimum HR of 75–95 beats·min −1 on average (mean 46% HR reduction) were similar to those found during dynamic apnea diving [35], [40], [41], and in SS during training exercises [3], [5], [13], [42], and was more pronounced than the 38% relative HR reduction observed during face immersion during low-intensity (80 and 100 W) cycling exercise [36], [43]. We should take into account that while synchronized swimmers perform several movements combining isometric and intense dynamic exercise, in most previous studies the subjects performed low-intensity, steady-state exercise with face immersion in water to elicit the diving response.…”

“…While apnea and facial immersion increase the parasympathetic tone causing HR reduction [34], [39], exercise increases sympathetic stimulation of the heart [3] and increases HR. So when the swimmer starts holding breath during the routines, both inputs compete with each other for control of HR [40] and O 2 flow to the exercising muscles, though the O 2 conservation diving response would finally prevail until the swimmer is able to breathe again.…”

Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

“…Apnea reportedly increases MAP in exercising humans (2,4,7,26,27,33,35). In the present study, we found that MAP was greatly increased during apnea in both the L and S groups, but the increase in MAP was larger in the L group than in the S group.…”

Prolonged dry apnoea: effects on brain activity and physiological functions in breath-hold divers and non-divers

“…The inhale phase lasted for 3.6 s and the exhale phase-for 3.2 s. On being subjectively ready for the breath-holding, the subject breathed out fully into the mouthpiece of a gas analyser to specify O 2 and CO 2 partial pressure in the final portion of the exhaled air (alveolar air). Then, the subject inhaled the ambient air from a rubber bag which contained 80 % of his vital capacity, as described previously (Wein et al 2007). The inhale ending moment ("collapsing" of a rubber bag) was considered to be a starting point of the voluntary apnoea, and the subject put his head on the cushion.…”