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

Can this lead to a serious issue or one needing medical attention? I am a 27 year old mother of two I haven't worked out in six years since my first child. I was an athlete before my kids track softball soccer. I decided to get serious about working out went to the gym three days in a row my routine was run a mile then work out each section of my body upping the weights until I maxed out then I'd run a half mile and call it a day. My endurance was higher then my bodies capability I'm guessing because by day three I was sick couldn't get out of bed couldn't eat could barely drink. My body was sore sure but nothing like the sickness in my stomach it's been three days and I'm still feeling the same intense sickness I can barely get anything down and I really feel like I have a stomach bug cold sweats sudden fever and just nausea
Constantly my husband threw out the theory that breaking down my muscles with weights releases toxins and working out my whole body so much after not lifting a finger for 6 yrs could have overloaded my body with toxins any truth to that I'm just start to wonder if I might have did some damage but I'm not in pain at all just really sick and honestly dying to get back in the gym but I don't wanna permanently hurt myself Ashley8689121346, Sat, 13th Aug 2016

To be safe and eliminate any serious problems it would be wise to consult a GP.
It is most likely one of the common causes such as the muscle demand for blood taking precedence over the stomach, in those circumstances the stomach tries to evacuate anything in there. Also, be careful not to under or over hydrate and avoid fatty food before exercise - although I would expect this would be second nature if you were previously an athlete.
I would certainly back off to an alternate-day programme until you acclimatise.
Colin2B, Sat, 13th Aug 2016

If you exercise beyond your body's oxygen budget, your body will go anaerobic, with lactic acid a side product, that will build up in your muscles. A build up of lactic acid can cause one to feel muscle pain and fatigue, as well as nausea.

In my youth, I used to run track and did the long sprints. After running a 400 meter race, sometimes my entire body would cramp up, combined with a feeling of nausea. This was due to too much lactic acid building up in my muscles due to my anaerobic over exertion.

The solution is to not just stop and rest, but to warm down. Warming down means don't stop, even if tire or not feeling good. Rather you keep walking slowly, deep breathing and stretching, to help the body process the excess lactic acid and to regain your peak blood oxygen. The impact of the lactic acid slowly reverses, and there are no ill affects.

Many people work out, until tired, but don't think about a warm down, to help stabilize the body. A warm down also trains the body to process the lactic acid faster. In fact, exertion, followed by warm down can train your body to build up a different aerobic fuel for your muscles, that can burn without oxygen, and not give off lactic acid; creatine phosphate. This anaerobic fuel is common with well trained sprinters and weight lifters. puppypower, Tue, 23rd Aug 2016

You are trying to do too much too soon. Slow down and work out in a more gradual manner. You have to increase your stamina and fitness slowly by small increments. Slowly increase your work load in small increments. Take a note book to gym with you and gradually add extra weight over time. Putting on heavy weights too soon will result in either injury or nausea caused by lack of sugar and oxygen. Atkhenaken, Sun, 11th Sep 2016

I noticed that when I was younger, my body was tighter. My stomach was always tight because I was always making quick moves, turns, bending over picking things up. I had a lot more jump in my step. My group of friends would always fake punches to each others stomachs, the silly fun things you do when you are young. I know that I digested food much faster when I was young.

Today I find that my stomach is not so tight, so when I go to work/workout, the relaxed comfort that I was just experiencing suddenly goes, with a slight feeling of nausea. Part of the reason is that as I start to work, moving heavy objects, I have to keep my stomach muscle tightened at all times. To brace my body against the muscles in my back. As this happens I constrict my internal organs. This is what was causing me the nausea. Now I do a quick warm up to tighten everything up before I start heavy work. So far so good.


Wiliam McCormick

William McC, Sat, 17th Sep 2016

Your stomach muscles hold your upper and lower body together. It is important to exercise your stomach muscles with sit-ups, leg raisers and crunches. Without strong stomach muscles your other body muscles will be useless. Atkhenaken, Sun, 18th Sep 2016

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