This was so true on the epic 88km Comrades Marathon this past Sunday. We following our normal running easy training approach, and arrived at the race day feeling fit, uninjured and ready for the task. HOWEVER - while all the days prior to this, and the forecast for Monday were all cool, today dawned baking hot.
The day would soar to temperatures around 30C but made much worse by a blasting hot wind blowing directly into us as we ran. It was so hot that every 10 minutes, after completely drenching myself in water, I'd have to do it again as I'd be bone dry.
There was only one way to approach this - and that was walk more, hold back, conserve energy. And that is exactly what we did. We walked much more, and ran much more in the first half, only coming into halfway (44km) in about 5h30. Quite a bit slower than we normally would. And even then the second half of this "ultimate human race" would prove to be extremely tough. In fact near the end as the 12 hour cutoff loomed I had to push more and more. Thankfully I had some reserves to call on unlike thousands of runners who collapsed along the road. If I had not approached this in a running easy way, I'm certain I would not have made it. But thankfully I squeaked in with just over 5 minutes to spare and joined 8,000 others who finished, while sadly 4,000 never made it.
The lesson - and I too need to keep learning it, hold back, try easier, and you can go so much further!