The Nervous System: an often overlooked piece to solving the digestion puzzle

One of the aspects of ultra running (or any running) that we talk about all the time is nutrition.

Ultimately everyone will have to find an individual nutrition strategy that works for them. Some people can eat cookies and burgers and Gu's and carry on for a hundred miles, other people are more successful with boiled potatoes and home made energy gels taken in small and frequent quantities. The only way you are going to know for yourself what works is practicing during training.

There are however some general strategies about how our body digests that everyone can keep in mind when eating on a run.

When you are working too hard, either stressed from going too fast or going hard climbing a hill or going very long, your sympathetic nervous system is diverting blood away from your digestive tract and toward your heart and muscles. Being aware of this physiological response is an important step in managing digestive issues.

The release of breath stimulates the parasympathetic response. It works on slowing your heart rate, and bringing blood back to your digestive system. Taking some intentional deep breaths can help calm that stomach. A good strategy for this calming breathing is inhale for 4 seconds, hold for 7 seconds, exhale for 8 seconds. Do this a few times, or for a few minutes. You will feel a change.


Some strategies for managing you digestion while keeping this information in mind:

  1. Don't eat at high intensity times. Like when you are flying downhill, or at the top of a really steep climb you are pushing hard on. Wait until you are levelled out (your heart rate I mean) on a flat, or on a gentle uphill. When you are working hard, and your sympathetic nervous system has kicked in whatever you eat is probably just going to sit there like a rock in your stomach. And when that happens it can be hours before you sort it out again.

  2. When you do find yourself with food sitting in your stomach like a rock or are queasy or however this shows up for you, take a few deep breaths. Intentional breaths, with a long and slow release. This is going to stimulate the parasympathetic nervous system. It will slow your heart rate and stimulate the digestive system. And then pop a ginger chew. That ginger will be more effective now than if you just took it when you were really revved up and uncomfortable.

  3. If you are having digestive issues and you are really hot, the two things may be related. When you are hot the blood vessels in your skin are dilated and the blood is pushed there to cool you off, that’s how we regulate body temperature. When this happens, again, that blood is diverted away from your digestive tract. Take a dunk in a river or just soak your head and shirt, it will feel amazing. And it just might be what you need to calm your stomach.

  4. If all else fails, take a break. REST = RESET.

Getting to the root of digestive issues can be a bit of a detective game. Don't forget about paying attention to hydration, the quantity of food you have eaten, and even when the last time you ate was. Every runner can benefit from knowing how the nervous system affects digestion to help them troubleshoot how to eat on a run.