HYPOXIC TRAINING HAS NO BENEFITS
Craig, A. B., Jr., (1982). Fallacies of "hypoxic training" in swimming. In L. Lewillie & J. P. Clarys (Eds.), International series on sport sciences, SWIMMING II, Vol. 2. Baltimore: University Park Press.
A trained male athlete was subjected to a series of controlled and uncontrolled breathing rates at various workloads on a bicycle ergometer. Even though this study was done on a bicycle its findings can be generalized to swimming training.
When breathing rates became insufficient to supply oxygen on demand, very unpleasant sensations were experienced and characterized by an "urge to breathe more."
Most experienced swimmers learn quickly that they can hold their breath or breathe less frequently by vigorous hyperventilation before a swim. Such practices should be avoided. The "training" that results from breath-holding practices is one of tolerating greater pCO2. It is difficult to see how such an adaptation could benefit a competitive swimmer.
Theoretically, it is possible that the initial retention of CO2 results in a slightly greater decrease in the pH in the muscles during exercise than one might have with normal breathing. This change would imply a slightly greater respiratory acidosis. The same result can be achieved by swimming faster while breathing normally.
Implication. Breathing less frequently does not accomplish anything that cannot be done by swimming faster. Hypoxic training is of no benefit to competitive swimmers.
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