As with hydration, I think that during the race, the best you can hope for is to top up your fuel stores as best you can. The body can absorb 90grms of carbohydrate per hour which equates to about 360 kcal.
In general running is considered to require about 500 kcal per hour. However this is a rough estimate. For a man of my weight running at my target pace of 6 min/mile the rate of calorie burn rises to almost 1000 kcal per hour.
Depletion is inevitable. The ‘wall’ isn’t.
Even if I consume 90g carbohydrate per hour, that will deliver around about 360 kcal which is less than I need to run at my target pace. However provided that in the days leading up to the race, I manage to eat well and top up the carbohydrate stores in my body – the endogenous fuel – there will be about 2,000 kcal that I have in my body to which I add the gels as I go.
The ‘wall’ is something I have encountered a few times – once in the London marathon – and it is pretty real. When it happened to me in the London, the change from feeling good and barreling along at 2hr 40min pace to shuffling through an aid station guzzling energy drink and gels, took just two miles – 15 minutes. Thankfully the recovery was equally swift and I was able to finish that year in 2hrs 43min. But I had missed my target by 8 minutes and those minutes were spent trying to refuel.
So my aim when I am racing a marathon is to buffer the endogenous carbohydrate stores that I have through the consumption of gels, in my case those from TORQ Fitness.
My plan in London this year is to take six gels during the race – one every 30 minutes – to keep the depletion of muscle glycogen stores to a minimum and to give the ‘wall’ a miss altogether. I would say that for most runners who are trying to race the best they can, a similar strategy will be beneficial.