The last few of weeks following on from the hypothermic Beast from the East have seen some of the highest spring temperatures on record and certainly the hottest conditions on record for the London Marathon with a lot of runners including elite runners suffering and slowing badly in the second half of the race. The usual culprit in this scenario certainly for a lot of the less experienced or first time marathoners is over exuberance in the first few miles of what is a fast course and allied to the extreme heat and little experience or practice in hydration and fueling techniques this can lead to a severe fall off in pace and potentially very serious problems in the second half of the race.
A lot of runners including experienced marathoners view preparation for a marathon as simply a question of maxing out on long runs and total weekly mileages interspersed with tempo runs intervals and the occasional hill session in the 14-16 week build up to the day with the basic thinking being that with all this mileage and quality trainingg under the belt the job is done. Yes most runners would have set for themselves a general race pace and split times plan based on their training and race times achievements and most runners will have a basic understanding of the need to hydrate before and during the race and to take on board some sort of supplementary fuel particularly during the second half. It is likely though that only a minority actually experimented and practiced hydration and fueling before and during the long runs in their programme.Given the conditions which transpired in London on the day this would have had major consequences.
When it comes to hydration and fueling needs each runner is of course different. However when it comes to hydration the basic principle is the same for everyone.We need blood to transport oxygen and nutrients to our muscles to enable muscular activity such as running and to dissipate skin heat generated by that activity and maintain a safe body core temperature. A major component in our blood circulatory system (our blood volume ) is water. We therefore need to be fully hydrated ( but not over hydrated) before a long run or a race and we need to replace what we are losing during a long run or a race. We lose water progressively during a long run or race so we should replace water progressively ie sipping not gulping.
So best advice is to use your longer pre marathon runs to practice fluid intake and as with your pacing and split times plan have a hydration strategy ready for the day. If as was the case with London it is forecast to be a “Midday Sun” challenge then plan to increase the relative amounts of water taken on board before the race and during the race to address the increased loss of fluid. Remember also to factor in a 3 or 4 extra degrees to the forecasted air temperature to allow for the reflected heat from the running surface the reduced air circulation resulting from the sheer volume of runners and the crowds the barricades and the building densities throughout the route.