This is a very good question. If you watch Michael Phelps or Jason Lezak swim freestyle you will see that they breathe on the same side every time. They seem completely uninterested in breathing on both sides. Many other swimmers race the same way. Phelps and Lezak also have a noticeable “lope” to their stroke – clearly not a balanced stroke. Other swimmers DO breathe on both sides and I am impressed every time I see it.

I favor my left side for breathing. I never breathe right when I race. Yet I alternate breathing in workouts because I want to improve my body position in the water. I breathe on the “off” side every other length during warmup, warmdown, and longer recovery sets. I don’t try every 3rd stroke because I want continuous repetition on my off side. I started this two years ago and my breathing on the right side is much smoother. I still breathe left only on harder sets because I need oxygen and it still feels best.

I also use a Finis freestyle snorkel several times a week. It removes traditional breathing entirely from your stroke – which allows you to swim balanced. I find this allows me to work on other stroke flaws too since I can look straight ahead and not worry about breathing.

Summary: it is ok to favor breathing on one side. But breathing on your weak side is useful to straighten out your body position. Do this in practice during sets that do not demand a lot of oxygen.