hey guys,

both my friend and i are lifeguards on a US military post.  i was wondering if holding your breath for long periods of time has any benefits or even harmful effects. 

there are 2 types:
1)remember the game you played when you were a little kid in the public pool? just hold your breath for as long as you can.  dont move or exert yourself in any other way.  i can hold my breath for about 1:30 and my friend can hold his breath for almost 2:30.
2)this is an exercise we see the army divers do (although im not sure if its for practicality or physical training).  its called a crossover: start at one end of the pool.  go under, kick off the wall, and swim to the opposite wall, typically 25m, without coming up for air.  i can do 35m, my friend can do 50m.

i know there a lot of smart guys on these forums when it comes to exercise and conditioning, so a critique of these exercises would be appreciated.

I think the idea is that it could improve your body on a cellular level by increasing your ability to perform with less oxygen.

This concept is interesting. Could this type of conditioning be an effective way of increasing lung capacity, red blood cell count, or anaerobic threshold?
I believe that it could do those things, but is it effective? Otherwise I would rather just breathe when my body tells me to.

Oxygen deprivation training (usually done in hypobaric training or at an altitude) only has an effect after several months of continuous prolonged exposure.  Simply holding your breath will likely not accomplish this with much efficacy.

Breath training, in all forms, is important only if it is important to you.  Erwan and i had a discussion once on it, when he pointed out that he not only trains breathing, but lack thereof.  when i asked him why, he said, "What if I need to dive very far, or if I am saving a person in a burning building, but there is too much smoke for me to safely breathe?  Can I carry a body and do what I need to do without breathing?"  But there's a fundamental difference between MN and Parkour...  It's much less applicable to us.

If it is something you need or you are compelled to, then great.  But if it's not, then it serves no purpose for you.

Wow!  A subject I have some useful imformation about, cool!  The skill of learning to hold your breath is called static apnea.  http://www.aida-international.org/ is the official site.  Check it out, I think it has some info on how to improve.