Question: What happens to your mucles after youv'e done a 100m sprint?

Phil Rice answered on 14 Mar 2013:

The muscles switch over to anaerobic metabolism (without oxygen that is). Lactic acid builds up as a result and the muscles build up a so-called oxygen debt. You pay this back by breathing very hard once the race is over. Ringing any bells! I certainly recall running the 400m as I hated long-distance and my muscles felt like jelly round the last bend.