I've just had some physiotherapy and when I said that I did freediving my physiotherapist said that she had just read an article about it here. It's quite good actually, have a read:
http://www.telegraph.co.uk/health/main.jhtml?xml=/health/2006/11/21/hfreedive21.xml#1
http://www.telegraph.co.uk/health/main.jhtml?xml=/health/2006/11/21/hfreedive21.xml#1