I have heard this before, but it never made any sense to me. I assume that the amount CO2 being produced is the same (for a given exercise level) whether we are holding our breath or not. If that is true, by exhaling we are not just reducing CO2 in your lungs, but also N2 and O2 (I do not think our lungs can selectively exhale only CO2) -- so by exhaling only we then put the same amount of CO2 into a smaller volume and thereby increasing the concentration of CO2 (in our lungs and thus also our bloodstream) compared to what it would be if we didn't exhale. I think the help from exhaling must come from a more complicated trigger to want to gasp for air -- the trigger (or at least the panic trigger) must take into consideration not just CO2 concentration, but also whether we are holding our breath (and exhaling doesn't get treated as holding our breath).

Who is Gary Hall Snr?


Would he ever bother to visit a triathlon forum?

(desperately trying to find an old thread where a question like this was asked before!)

Speaking of "surfing on bubbles".

I seem to recall some of my best swim splits when I would get in behind one or two much stronger/faster swimmers, and it was like swimming in a washing machine - lots' or turbulence and bubbles - but you would just hang on for dear life. The sense of feeling was at the time, that this was slower - but the actual swim split belied that point!

There seemed to be two types of better swimmers - ones like the ones mentioned above where it was rough and tumble in the water behind them and then the ones were there seemed to be little disruption at all - very smooth. It always seemed to be to be faster drafting in the washing machine, while it did not seem like it at the time!

While the CO2 thing is true, breathing can be dumbed down to even simpler principles. I did a post on "Pulse breathing" a month ago, to zero replies/crickets...

1. Use the stroking arm to assist in exhaling, therefore max flow out is during the pull (either side).
2. Maintain exhale flow but reduce when the chest is not under tension - this also applies for the bubbling effect
3. You have to work against water pressure, so its best to align with chest cavity muscular compression and with lowest pressure (ie a good exhale just as turning to breathe in)

I think top swimmers naturally do the above, without even a thought.