You gotta stopwatch? wrote:
Anyway, all they are trying to do is warm up their core and muscles a degree (C) so the muscles will contract more forcefully.
No they're not. The main purpose of a warmup is not to literally warm the muscles. It's to prime dormant energy systems so they're ready to contribute. You want to "go lactic" as a previous poster put it.
It depends on the particular race, the conditions, and the preferences of the athlete, but three or four minutes at HM pace at the end of a very slow jog is normally enough for most people. I like to start at a shuffle and allow myself to very slowly accelerate through the warmup until I hit threshold pace towards the end. The sensation I'm going for is that I'm holding myself back the entire time. A warmup like this should be completed at least 20 minutes before competition.
In hot weather, at distances longer than 5k, literally warming up is problematic. Lots of athletes in hot conditions will take a very short warmup for a 10k, and they'll do it in an air conditioned area if possible. The tradeoff of not having one's energy systems totally ready to go at the gun is worth it in a hot 10k because the accumulated body temperature over the course of the race is a bigger factor.