Sadly there isn't much to learn from the altitude to underwater hockey analogy. And I'm further not certain that any of the physiological models have anything much to do with explaining what one earth happens to us as UWH players.

This is because sustained hypoxia is turning out to be an entirely different beastie to intermittant hypoxia in the disease models of chronic obstructive pulmonary disease (sustained hypoxia-emphysemia for example) and obstructive sleep apnea (intermittant hypoxia). The intermittant hypoxia is becoming recognised as a major risk factor for cardiovascular disease (CVD). Which got me wondering about how many of the 40-60 year old otherwise fit UWH players were coming down with CVD. Does UWH cause CVD?

The problem is that we're not even sure that UWH causes intermittant hypoxia. Liam and I have both tried to hold our breath while attached to a pulse Ox and haven't gotten the thing to move at all. Even past two minutes I couldn't get below 97%. COPD patients are chronically below 90% and severe OSA patients have intermittant drops sometimes into the 50s and 60s% and regularly below 90%. You normally need very bad lungs, low oxygen level sin the air (altitute or trapped in an enclosed space) or breathholding on an empty lung to desat (like sleep apnea). So I'm not sure whether we even get ox desaturations from UWH. Would be very hard to measure.

Respiration rates in normal people are determined by three major factors. First CO2 levels as Al has already said. 2nd Ox levels. 3rd acid-base levels in the blood (not as important but can be experimentally manipulated- usually a product of the mix of co2 and o2). Breath hold above that is something else. General cardiovsacular fitness for a start and a combo of will power and training at holding your breath seem to be the leading modifiables. Like Al said.

Interestingly my response to low O2 when subjected to about 70% of normal is quite blunted. It takes a while for respiration to speed up. I've never heard of another hockey player being given the same test though. It could just be me. I also don't know whether UWH players have more red blood cells than equivalent sportspeople (eg a soccer player).

Sadly for us all there's no real research and we don't know what UWH players are really doing.

Liam. Perhaps you want to tell your story about high alt training again just below my post?