Going faster on the second half than in the first of the race – what we call negative split – is something most athletes learn to master with experience, but it’s also how you will get the most out of your fitness. Nearly everyone experiences a significant disconnect between heart rate numbers and rate of perceived effort in the first hour of these events. If we talk about triathlon only, this will be felt on the first hour of the bike leg. What I mean by this is often you will feel that you are going too easy, almost effortless, but your heart rate and effort applied is telling you something quite different. It can take up to a few half an hours for your perceived effort starts to match your heart rate, especially on very fit athletes. Knowing this in advance before entering a race will make it easier to back off a little, especially on the first third or even half of the bike. If so, it will be unlikely you will blow up or that you burn too much energy in that first half.
There are many factors that can influence the speed in which you accomplish the distances split in half such as winds, changes of temperature, etc, so the best way to make sure the effort will be a negative split is to look at the metrics that don’t rely on emotion – heart rate or power. Mental and physical fatigue usually sets in on the second half of any race and by staying within yourself at the beginning will create the mental and physical reserve for when it gets grueling. No matter what course you will do, the second half of any long distance race is the hardest. Even if it’s all downhill.
Besides the perceived effort of feeling “easy”, you will also realize that most of your competitors will not race this way. They are overwhelmed by the excitement level and even if you go into a race knowing you should back off, it will be very easy to ignore that preset once people start to go by you in the first miles. To avoid this, gaining confidence and experience will be fundamental for success. You will fail a million times, before you get one right and prove that your best race came out of your negative splits. It then becomes easier to back off the next time, not to ignore the early disconnect between actual effort and perceived effort and not working too hard without realizing it.
The longer the race, the best this will play out in your favor since the more hours you are out there, the more you will “pay” for how hard you went and you were feeling so strong. And there’s always room to correct your first third or half of the bike – if you felt like you went too easy, go ahead and go harder on the second half. You will always have an opportunity to correct your “too easy” moments later on the race and the same doesn’t go around. If you rode too hard, that mistake will have 20, 30, 40 or 50 miles to express itself and pull you back. No one will look at your first third bike split, everyone will look at how well you finish the bike and were able to run.