I will agree with many of the others here and say that there will be a CO2 tolerance benifit…I suppose you could call that a physiological adaptation…But the larger point here that everyone seems to be missing is that it is still hard swimming going on while doing this…You all are acting like it is a breath holding exercise in the hot tub…Now that I would call a waste of time, but swimming 10X100’s with a breath hold 25 in the middle a waste of time??? Come on guys, swimming hard is swimming hard, and all of it will benifit you…If it is only psycological, well that has its benifits too…I don’t understand how something that we know almost ALL fast pool swimmers do, and have done for ages, is somehow going to be some waste of time for triathletes aspiring to always become better swimmers…There are lots of things that are not nessecary to be a triathlete, hell, from what I have seen almost anyone can be one…But when you finally get to that top 5% of the heap, there are lots of things you can do for those little edges to shave seconds on race day…I would venture to say that tons of people have lost groups around buoys because they got hypoxic, panicked, and lost their groups…I for one would like a tool that got me through those little episodes, and kept me in the group…