Negative splits are positive
What works for best performance in a long run or bike ride? Start hard and push it as far as you can, or start in a more comfortable speed and increase at the end? It's the latter, when your mile (or km) times are getting faster as you go (negative splits), you are more likely to reach your best time. This is well known, and I have also tested it for myself on the treadmill. To the left is an example of negative splits on a recent training run. Starting too hard is always a mistake, you cannot will yourself to keep it up to the end, your body is actually unable to respond. I am not going into the physiology of why, but I have enough experience to say that a too ambitious opening will fail to make a good time and it's not a lack of willpower. When I did my half ironman earlier in the year, I was just focused on completing the course, not to reach a specific time or place. I managed the energy well, holding an even pace, and the final run ended up as my best performance ...