BTW, although the sodium bicarbonate may help with lactic acid, it would actually make the diarrhea problem worse, not better. Eric Fattah wrote about it more than once here on DB: check out for example the following threads. And unlike the above mentioned research he also denies positive effect on the breath-hold time:
http://forums.deeperblue.net/freediv...tml#post215994
http://forums.deeperblue.net/freediv...rch-study.html
http://forums.deeperblue.net/general...rformance.html