Glycogen & ‘Hitting the Wall’

Everything that we do requires energy – so what happens when we run out? It’s not as easy as filling the car up at the petrol station. Fortunately our bodies can source energy in a number of ways, but that doesn’t mean we can’t run out.

The phenomenon of hitting the wall is attributed to endurance athletes who suffer the very real problem of running out of energy. During exercise we source energy through either fat metabolism or the breakdown of glycogen into glucose. It’s not just a case of picking which one you fancy at the time though – as you perform more intense exercise the body relies more on your glycogen stores to provide energy, not fat.

As a result when our glycogen stores, which are found in the liver and muscles, deplete following exercise, the possibility of hitting the wall is very possible. Without providing the body with more energy levels of glycogen constantly drop during exercise. Now generally that wouldn’t be a problem, providing your nutrition is relatively sound. But when you’re doing endurance exercise it is something you need to be aware of at all times.

Just like the battery life on your phone, you don’t have to wait for your body to run out of glycogen before you charge it up again – and this is a good way to think about it. Imagine the glycogen levels in your body is the battery life in your phone, and just like the battery life in your phone, there are a number of ways you can avoid running out.

The first thing you could do is charge your phone to 100% at the start of the day. Similarly you can aim to maximise your glycogen levels prior to starting any endurance activity. This can be done through carbohydrate loading of foods with a high glycemic index – meaning that the food has a high rate of conversion into blood glucose. Even the foods with the highest glycemic index will only replace between 30-40% of the glucose in your body once you start exercising close to your maximum level though.

The other thing you can do to your phone is increase its ability to hold charge (close running apps, reduce brightness, turn off Bluetooth etc.). In the same way you can set your body to be more efficient with its fuel too. By improving fuel efficiency your workload capacity will increase, but what’s more is your body will use a greater amount of fat to produce energy, reducing the dependency on glycogen stores.  This is a long process though – it can take months of long-distance running/swimming/cycling to notice a real change in your body’s fuel efficiency.

Finally, you can simply wait for your phone to run down to 0% and then charge it back up. You might have heard that it’s good to let your phone battery run completely dead every now and then. I can’t comment on whether that is true or not, but what we do know is that consumption of carbs following/during exercise in large amounts increase the storage capacity of muscular glycogen.

This idea of hitting the wall can also be used to lose weight – although I would guess if you are a keen marathon runner or long-distance cyclist, that might not be your primary goal. Nevertheless theories do exist surrounding it. One suggest exercising on an empty stomach while caffeine levels are high (e.g. after a cup of coffee) to force hitting the wall to occur more rapidly. As a result when you stop exercising your body has no choice but to use fat stores to supply energy.

This is something I would strongly discourage though. Not only is it an unproven theory, but trying such extreme methods can often be dangerous. There are so many tested ways to lose fat – why would you want to risk your health with this method?

We have all probably experienced hitting the wall at one point or another. Exhaustion sets in, and you can often feel ill, dizzy and even get headaches. Unfortunately rest and fluids will do very little for you in this case though. The rather poorly kept secret is carbohydrates. Get those glycogen levels up and you might even be ready to go head-to-head with Mo Farah in a 10,000m race.

Ollie Lawrence
Latest posts by Ollie Lawrence (see all)