Yesterday I tried a 5-mile tempo, and side stitches almost ruined it... I got some after a (too fast) 6:30 first mile, and though I managed to control it until mile 4.5, it came back so bad, that I was physically unable to run or walk -seriously, I had to stop. I was standing for about 10 seconds, then I could run again, and finished the last mile in 7:00. The splits were 6:30, 6:54, 6:41, 6:52, 7:00 for an average of 6:48. Which is not bad, but I have to get better with pacing. I think I'm not used to my new endurance. I used to run tempos just going out hard, and maintaining it for 20-30 minutes. Now I have to run over 30-minute tempos, and I have a speed that if I go out hard, I'm too fast at the beginning. My physiology has changed, and I didn't adapt mentally. I will have to start the tempos, and especially the races slower, otherwise I will crash and burn.