Frankly, I used to think it was a good idea to partially exhale before doing exercises like leg press to avoid increasing the blood pressure but … in general I believed, focusing on a certain style of breathing was a waste of time.
However, that was before I encountered “20 second repetitions.”
This method of training is a whole different world … you just run out of breath. Furthermore, you can’t take a big breath and hold it or even another big breath right in the middle of the rep because when you’re straining … it’s hard to breathe.
By panting (short quick breaths) you can keep your blood stream full of fresh oxygen to counter the build up of lactic acid. Also, it doesn’t require a big expansion of your rib box.