Post-exercise nausea: why do I feel sick and sometimes vomit after exercise?

Post-exercise nausea can be brought about by a large number of things. But the root cause can usually be traced back to some kind of basic disturbance of homeostasis (the body’s preferred, stable internal status) and the following are a few common culprits:

1. Unaccustomed exercise intensity. In other words, if you go really hard during a session or race and you’re not conditioned for it, this can leave you feeling rough. Being gently progressive in your workouts and training very specifically for the demands of racing are the best fix.

2. Screwing up your nutritional intake. Either eating too soon before exercise, eating too much or eating way less than you need to are all common causes of feeling sick during or immediately after exercise. To combat this you need to work on improving your nutrition plan and trying out some different strategies until you figure out what works for you.

3. Over-hydration. If you over-drink, especially plain water, during exercise, nausea can be a sign of impending hyponatremia (low blood sodium levels) so don’t be too aggressive with fluid intake and take some electrolytes (sodium in particular) if you have a high sweat rate.

4. Overheating. Sickness can also be a sign of a large rise in core body temperature. Pacing yourself and employing tactics to keep cool obviously help and are necessary if you’re training and racing in the heat and prone to sickness afterwards.

Of course, there can be other issues leading to post-exercise sickness such as ingesting bugs or bacteria (common in triathlon if the swim is in poor quality water), but the above checklist is a good place to start if this is regularly happening to you.

Sports scientist Andy Blow is a former top Ironman and founder of Precision Hydration, which specialises in tailored sports hydration

Andy Blow Sports scientist

About

Andy Blow is a sports scientist with a degree in sports and exercise science from the University of Bath. An expert in sweat, dehydration and cramping, Andy previously worked as the team sports scientist for the Benetton and Renault Formula 1 teams, and remains an adviser to the Porsche Human Performance Centre. He specialises in electrolyte replenishment and founded the company he now runs, Precision Hydration. An elite-level triathlete in his younger days, Andy has finished in the top-10 of Ironman and Ironman 70.3 races, as well as winning an Xterra world title. Andy has also worked alongside Dr Raj Jutley, as well as other top sports scientists, to co-author a number of studies and books which have been published in BMJ Journals, the Journal of the International Society of Sports Nutrition and the Journal of the Endocrine Society.