What is ‘hitting the wall’ when running and what happens?
Hitting the wall refers to a state where after intensive running, cycling, or such sports, the athlete suffers a state of sudden fatigue and loss of energy. This is caused by the loss of glycogen stored in the liver and muscles. To avoid the condition, the athlete must make sure that their glycogen levels are optimal and will be able to endure the entire race. This is done by eating and/or drinking substances rich in carbohydrates.
How Does a Runner "Hit the Wall"?
To understand the mechanism that triggers this negative feeling, we must turn to two very important substances in your body: carbohydrates and fats. These are the fuels that your body needs to operate properly. You are constantly burning a blend of these two. However, the ratio of these fuels changes as you increase the intensity of your activity.
During a speed workout, you will burn a large amount of glycogen. During a slow run, you will be burning more fat than carbs. If we break it down to math, we can see why most runners seem to be close to hitting the wall after 20 miles into the race. Glycogen is stored in the liver and muscles with a total of 1,800 - 2,000 calories. We burn around 100 calories per mile of running.
What Happens when a Runner Hits the Wall?
Since there is a depletion of glycogen in the body, the body runs out of fuel and, just like it would happen with a car, it stops working. Usually, the sensation of hitting the wall includes sudden fatigue and not being able to go on anymore. Dizziness and some muscle cramping may accompany it.
During a long marathon, runners could replenish the body with the carbs needed by drinking high-carb drinks. Another way of doing so is to reduce the intensity of the workout to resort to the use of fat.