The medical definition of hypoxia is a pathological state caused by an inadequate oxygen supply to the entire organism. Hypoxic training applied to swimming refers to a specific type of training performed using a different breathing pattern to the conventional method of breathing every stroke or every three strokes.
Hypoxic training was initially intended to simulate altitude training, where the partial pressure of oxygen in the air is reduced and so oxygen flows through the blood more slowly. Studies*have shown that hypoxic training does not reduce the oxygen flow to tissues, nor does it recreate the conditions found during altitude training.
So what is the real benefit of hypoxic training? The ability to hold your breath longer.
Hypoxic training brings about a state called hypercapnia (from the Greek hyper: over or too much, and kapnos: smoke) or, in other words, an increase in the carbon dioxide (CO2) levels of the blood. So hypercapnia triggers off a breathing reflex. If you struggle to hold your breath at certain times while swimming (during the exertion of a race or a prolonged underwater phase) it is the amount of carbon dioxide in your body that increases and not the oxygen supply, and this means you will need air.
How often you train is important. The more you practice holding your breath, the better you will become at controlling this reflex, so you will be able to swim longer, breathing less.
That is why hypoxic training is excellent for freestyle and butterfly swimmers, but not only them. Backstrokers will notice the benefits during the underwater phases using the butterfly leg kick, and breaststrokers will also be able to improve by practising this skill during the underwater phases.
You can improve your technique very quickly, mitigating the effects of hypercapnia in just a few weeks and teaching your body how to breathe less when necessary.
Here are some simple exercises you can include in your training sessions to learn this skill:
– From 4-8 X 25 metres freestyle with 1.00 rest in “hypoxia 1”, i.e. only breathing once every 25 metres. When you feel confident with this kind of training, try and alternate it with “hypoxia 0” or, in other words, without breathing for the entire 25 metres.
– 4 x 50 metres freestyle with 1.00 rest, attempting to vary how often you breathe during the 50 metres: to begin with try breathing once every 25 metres and then try swimming the first 25 metres without breathing and the second 25 metres breathing only once.
– 3×100 freestyle with 1.00 rest, altering your breathing pattern every 25 metres: breathing every 3 strokes for 25 metres, then every 5 strokes for 25 metres, then every 3 strokes for 25 metres and every 7 strokes for 25 metres.
– 8×25 butterfly leg kick during the underwater phase with 1.00 rest.
– 4×50 metres swimming 15 metres underwater with a butterfly leg kick off the wall at the end of each length
Last but not least, remember hypoxic training is physiologically stressful, so you are advised to introduce it very carefully into your weekly training sessions.