The physiological responses to breath-holding during high-intensity land-based exercise and swimming.
Abstract
The overall aim of this dissertation was to determine the effects of breath-holding during high-intensity exercise. The response to breath-holding is known as the diving response and includes bradycardia and peripheral vasoconstriction, whereas the response to exercise includes tachycardia and peripheral vasodilation. When breath-holding occurs during low-intensity exercise, the diving response prevails, but which prevails during high-intensity exercise is unknown. Study One examined recreationally active adults performing simultaneous arm and leg ergometry at high intensity for twenty seconds with and without breath-holding. The exercise response prevailed considering heart rate was increased during breath-holding compared to free-breathing and this may have ensured sufficient oxygen delivery as there was not an increase in oxygen extraction at the muscle, or anaerobic glycolysis as determined by near infrared spectroscopy and blood lactate concentrations, respectively. Study Two examined the effects of breath-holding during high-intensity exercise in competitive swimmers habituated to breath-holding, as habituation enhances the diving response. Using the same methodology, it was found that despite signs of an enhanced diving response (increased systolic and diastolic blood pressures, indicating peripheral vasoconstriction), the exercise response prevailed. Increased heart rate may have ensured sufficient oxygen delivery considering there was not an increase in oxygen extraction at the muscle, or anaerobic glycolysis. Study 3 examined the effects of breath-holding during high-intensity swimming, as immersion of the face in water enhances the diving response. There was no difference in heart rate between breath-holding and regulated breathing, and the additive effects of facial immersion and apnea may have overridden the exercise tachycardia that was observed in the land-based studies. There was increased oxygen extraction, suggestive of vasoconstriction, at the triceps brachii muscle, due to breath-holding. Although the diving response was evident during high-intensity swimming, it did not appear to impair performance, possibly due to the short duration of exercise. Overall, it appears that the exercise response prevails over the diving response during short-duration, high-intensity exercise. These findings suggest that if there are biomechanical benefits due to not having to turn the head to breathe, breath-holding during sprint swimming should be considered a viable strategy to improve performance.