It depends on what you want to exercise really. Breath-hold exercises won’t make your muscles get stronger faster or anything, but they will improve your ability to go extended times without air, which is a useful talent in itself and improved lung function is helpful for maintaining higher rates of exertion for longer.
So… Exercise what you want to be able to do I guess?
This is one of my favorite crackpot writings. It does seem plausible that held breath underwater swimming is really good exercise. http://www.winwenger.com/ebooks/guaran.htm
Any sort of swimming is good exercise. Hypoxia, however, is bad for you… IMO it’s better do the swimming with the oxygen ;)
It depends on what you want to exercise really. Breath-hold exercises won’t make your muscles get stronger faster or anything, but they will improve your ability to go extended times without air, which is a useful talent in itself and improved lung function is helpful for maintaining higher rates of exertion for longer.
So… Exercise what you want to be able to do I guess?