Science Questions

Why do I feel sick after exercise?

Thu, 20th Jun 2013

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Ari Huttamen asked:

I'd like to ask a question regarding a too intensive workout and a sometimes occurring sudden nausea during or afterwards. What makes this happen and what happens in the body?


This thing happened to me when I began working out seriously about three years ago at the university. It never happened in the gym, but in intensive group exercise sessions, like cirquit training and boxercise. Back then I think it was about learning not to eat too much an hour or more before the exercise. However recently I felt nauseous and weak and I think this was just because of too much exercise, not eating wrong.


The experience is quite strange, I feel dizzy, everything in my stomach attempts to get upwards and stuff in my gut starts to makes it's way down quickly - pardon the graphic description. Basically you need to think quickly where's the nearest loo, just in case.


So I'm interested what makes this happen, what kind of stress this is to the body and what the body gets from reacting this strongly?


David - I'm David Weston, a PhD student in neuroscience at the University of Cambridge. Feeling sick after exercise is something that most of us are pretty familiar with, especially if you exercise Exerciseas infrequently as I do. But why does our body and our gastrointestinal system re-assert itself after a run around the block?

Well, exercise is very physically demanding and your body reacts by increasing blood flow to your muscles and your heart and your lungs, and your brain to keep your body able to process energy and keep your muscles going. This diverts blood away from your visceral organs like your stomach and could deprive your gastrointestinal tract of the oxygen it requires to function. This symptom is called ischemia and is believed to be one of the reasons why you might feel sick after intense or prolonged exercise. Now, ischemia can in very severe cases damage the lining of your stomach and cause the bacteria in your stomach or the toxins that they produce to enter your bloodstream.

So, some evidence also suggests that gastrointestinal distress is caused by what you eat and drink before exercise. One study found that foods with higher fat and protein content were linked with nausea and vomiting in triathlon runners. Other studies even suggests that taking aspirin before you exercise could increase your chance of gastrointestinal discomfort.

Exercise also increases the levels of hormones released in the brain that control processes like thermoregulation, so your ability to maintain your body temperature. And this drives sweat to the surface of your skin and cools you, but can also result in dehydration. So, a loss of fluid can decrease your blood pressure and could lead to the kind of ischemia that I was talking about before.

Hannah - Thanks, David, and poor Ari is not alone in experiencing this phenomena. Jean Kennedy says that she just simply cannot do most forms of floor exercises. She apparently goes green with nausea if she does, whilst a second listener also had this to say on a matter…

Ross - Hi. I'm Ross from Birmingham. This is something that I've experienced it in the past and it can be quite uncomfortable. Having sought some medical advice, I found that eating properly, well in advance of exercise and being well hydrated before and during exercise that the problem went away.

Hannah - And David agrees with this advice.

David - Well, current research suggests that you can reduce the likelihood of nausea and vomiting by ensuring that you don’t eat three hours before intense exercise. And also, keeping hydrated is key, so don’t forget to drink plenty of water.


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hi David; I'm Phelix from Kenya my problem is that after just a small exercise like even running,long walks jumping or playing football....i begin to feel pain in the joints, cold, headache and I lose appetite...pls advice mi on the medicine i need to take phelix, Mon, 30th Dec 2013

Is there a link with blood pressure? Mine causes postural hypotension which means I feel sick and faint if I get up quickly in the night. I'm wondering if the symptoms after exercise (weak, dizzy, sickly feeling) are caused by a similar thing. Kez, Thu, 2nd Jan 2014

Lets not forget other things that are not necessarily gastrointestinal in nature that can cause feelings of nausea. For example, not having adequate blood glucose prior to intense exercise can cause you to feel quite lightheaded which is often accompanied by nausea. As stated above, dehydration can cause nausea and lightheadedness as well, but I doubt this is from bowel ischemia. The more likely reason is decreased intravascular volume causing symptoms much like postural hypotension. I believe exercise induced nausea to be multifactorial and can be of completely different origins in different people. John, Fri, 24th Jan 2014

Try taking some kwells beforehand Craig, Tue, 25th Mar 2014

if u feeling nausea after workout then try to calm down and do fo for vomiting.... take a rest for 1 to 2 hrs.. your body will respond smoothly aftr rest and you ll b as normal as you wer before workout. don't lose hopes.. next day again start the workout without any hesitation and continue the process... after few days your body will adopt to this situation. MANGESH DHERE, Wed, 11th Nov 2015

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