I recently ran a 10K race after not doing the proper thing and getting a good night's rest the night before (party, party, party !). I was umming and arring whether I should run or not on the day as I felt like s**t, but opted to run anyway, but take it really easy. Anyway, my legs felt really tired, and for the first 8k I was in the 170s bpm region, some 20 bpms higher than normal. I felt pretty good in the final 2k and managed pick up the pace quite considerably. Using these stats does this mean that I should be able to run at 170s bpm on a rested body, and thus potentially finish in a far faster time than I have done previously, or was the increased heart rate a false indication of pace because I was knackered? Got another 10k coming up soon and would like to try things out at the faster pace, but wouldn't want to burn myself out and not finish.