Battling Nausea After a Big Race

Many runners report nausea after the effort of a marathon.

There are basically two causes of vomiting: disturbances in the gastrointestinal (GI) tract and disturbances in the central nervous system (CNS). The common CNS disturbances in sport are concussion (not common in runners), exertional heat stroke, and exercise-associated hyponatremia (excess fluid intake).

If you can rule out heat stroke and hyponatremia, it may be worth considering GI disturbances.

The GI system can be affected by running. The demands of running can cause reduced blood flow to the GI tract so that more blood is available for oxygen, nutrient, metabolic by-product, and heat transport to and from your muscles. In this situation, the fluid you ingest may not be well absorbed, which could result in you losing those fluids after the race.

If you find you are a very heavy sweater, some studies suggest that the gut stops absorbing fluid, you become nauseated, and eventually vomit. This is especially true for those who are dehydrated before they start to replace fluids during exercise.

There are some people who vomit following intense exercise, especially when it is more extreme than your body is accustomed to. This could happen to runners who really push the last kilometre or two of the marathon.

If you feel this may be your cause of nausea, start by checking your prerun and postrun weight to get a feel for your sweat losses. You need to be careful to not exceed your sweat losses with unnecessary fluid replacement. A general rule of thumb is to just drink when you are thirsty. Do not push fluids when racing.


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