Lisa asks: Why do I get sick after racing a half marathon or 10K? When I do long runs I never have a problem.
I’m not sure if your symptoms strike immediately after your efforts, or if you fall ill in the days following a race. I’ll cover both situations to hopefully help.
Some people vomit or get very light headed immediately following a race. Vomiting is not uncommon following hard exertion and happens to many people. The vomiting may have to do with the blood flow to the gut and the adrenaline and other stress-related hormones mobilized during the race. You may not experience this during training; I think the excitement of competition may play a role.
The exercise-associated dizziness is due in part to the loss of the leg muscle pump that squeezes blood from your legs back to your heart. When you stop running, that assist rapidly disappears and temporarily reduces blood flow to the brain. Continuing to walk or jog after you finish can help reduce this problem. If continued movement fails to resolve the problem or the symptoms are too severe to continue walking, lie down with your feet propped up.
Regular moderate exercise seems to improve immunity and reduce the number of respiratory infections in habitual exercisers. There is a phenomenon referred to as the “open window” that follows endurance racing (usually at the marathon distance) and exhausting workouts during which there is an increased susceptibility for respiratory infections. This “open window” is a three- to 12-hour period of time after heavy exercise when the immune-system defense is less able to react to infecting agents like viruses, and the risk of becoming ill increases.
Avoiding sick contacts around race time and not racing when ill can reduce your risk. Pre-loading your immune system with an annual flu shot and other immunizations will also reduce your risk, but will not completely eliminate it.