The London marathon fast approaches (just 4 full days to go) and thousands of runners, both professionals and amateurs will be gearing up for what should be an amazing day. However one of the biggest threats to a successful finish is “the wall”.
What is the Wall? Many marathon runners, especially first timers or those who had problems completing a full training schedule report the wall as being exactly that – an invisible wall that you can’t run through. Leaden legs, sudden lethargy, mental wobbles and above all the feeling of pushing against an unseen immovable object are symptoms of hitting “the wall”. Many sports have “the wall”. 400m runners usually experience it after 250-300m. A feeling of “I must stop, there’s nothing left”. From personal experience I can report there is a big wall in 2000m indoor rowing – around 800m in you look at the display, see more than half the race left, and realise that you’re spent. This is the wall.
In physiological terms the wall is actually depletion of energy. One of the flaws of human physiology is our limited supply of fuel, or glycogen. Sometimes known as blood sugar, our large brains demand high levels of glycogen. With this constant supply needed there’s only so much readily available glycogen left in our fuel tanks – the liver and muscles. The liver can hold around 100g, the muscles around 400g. There is also a small amount available in the blood and kidneys. If we translate this into calories, the average man weighing 70kg has around 1,800 calories worth of glycogen available for exercise.
Calories used in running
Both available glycogen and how long it will last depend on many factors; an individual’s fitness, weight, exercise intensity and genetics will all affect calories burned. But Harvard Medical School report that the average man running at 5.2mph will burn 670 calories in one hour. Take in to account the 1,800 calories available and we can see that the wall will happen between 15 and 20 miles into the marathon (2-3 hours). Most well prepared runners report hitting the wall at the 18 mile point.
Hitting the wall – the perfect storm
It just so happens that around the same time people begin to run out of fuel, other factors kick in. Muscle pain and damage start to build up, aches and pains in the back, hips and knees build up creating a point of misery that can destabilise or even end the race.
Is the wall inevitable, or can I have a wall-free race?
As above there are many variables that effect how hard and soon the wall will happen. Mental strength is a big one – this can only be built up through training and taking yourself close to the limit regularly.
Physical training is also a massive factor. A general rule is that in a distance race you need to have done at least one training session that covers 80% of the whole distance. In a marathon this would be 22 miles. Those that don’t go as far in training will be more likely to suffer.
Become a fat adapted athlete – most beneficial for distance athletes, this means that you can rely more on fat as a fuel source during exercise. This spares glycogen stores making them go further. It will also incidentally help those targeting weight loss to adapt to burning more fat (as opposed to glycogen) in low activity situations – at work for example. Techniques to become fat adapted will encourage the body to dip into fat stores when glycogen is depleted over time. These are feast fast routines (like the 16:8) and fasted training (best done in the off season as it may limit the quality of some workouts).
Taper properly. The taper is where sessions become shorter and less strenuous as the event draws close. Most tapers go down to several days of full rest before a race, with only short high quality sessions before that. They usually last 2 weeks. Not only does the taper allow muscles and connective tissue to adaptively strengthen and repair, less demand for energy will help build up glycogen stores.
Carb loading. Increasing the amount of carbohydrate (especially unprocessed starch like brown rice and pasta) will help ensure full fuel tanks at the start of the race.
Race nutrition strategy. Drip feeding glucose into your system during the race is essential. Aim to take on a small amount of sugar every 30 minutes. This pre-emptive approach avoids falling low and then trying to refuel, which is much harder. It will also avoid any tummy issues like cramping or even worse an emergency bathroom break. About 20-30g of carbohydrate at each ½ hour refuel should do it. Race nutrition training is also important. So you should have been doing longer training runs with gels, drinks or jelly babies. This trains the gut to smoothly take on fuel while running.