By Dan McCarthy//National Team High Performance Consultant
The topic of hypoxic training has seen increased interest recently, notoriously at times because of increased awareness over shallow-water blackouts. Most swimmers are familiar with hypoxic sets, or breath-control training. Popular sets usually require athletes to limit their breathing once every five, seven or nine strokes during a repeat distance or throughout a set. A more extreme version of hypoxic training involves “no-breather” 25s of freestyle or butterfly. The risks associated with limiting oxygen use to humans is obvious; however, do advocates of hypoxic training understand what benefits can and cannot be derived from such training?
Most importantly, hypoxic training is not like altitude training. Altitude-training requires athletes to breathe less pressurized air, which results in less oxygen; but hypoxic training requires athletes to breathe less often. The practice of altitude-training forces athletes to become more efficient with the oxygen they inspire by producing more red-blood cells. Hypoxic training raises the level of carbon-dioxide in the bloodstream, increasing feelings of discomfort. While hypoxic training is constantly being investigated by organizations like the U.S. military, at this writing research regarding the hypothesized beneficial physiological adaptations has been inconclusive.
Proponents of hypoxic training can root their practices in the writings of Ernie Maglischo. Coach Maglischo, in his excellent book Swimming Fastest, dismissed the far-reaching possibilities of hypoxic training and wrote about the one adaptation it can be associated with-Hypercapnia. Hypercapnia is responsible for the urge to breathe when one is holding their breath. According to Maglischo, breath-holding training can increase the ability to resist this urge. He felt as if such training may assist a freestyle or butterfly swimmer in learning to swim each 50 of a race with fewer breaths.