- Adam Taylor
- Talk *
Many people exercise to feel better. But while some are thrilled after a workout, others are sadly leaving the gym with nausea.
Although the discomfort is usually only temporary, it can still be uncomfortable.
Fortunately, there are some good explanations for why this can happen – so if this is your case, there is probably no reason to worry.
When we exercise, there is an increase in blood flow to the working muscles, brain, lungs and heart.
This increase in blood flow triggers the sympathetic part of the autonomic nervous system (which helps regulate all of our body’s involuntary reactions such as heart rate, blood pressure and digestion).
And it does so by dilating the arteries so that they can carry more blood to these tissues.
But the sympathetic nervous system, which otherwise activates our “fight or flight” mechanism, simultaneously narrows the blood vessels that enter our gastrointestinal system (such as our stomach) during strenuous training by up to 80%.
And this is because there is a limited amount of blood in the body, and the increased oxygen demand of some tissues can only be met by changing the amount of blood that goes to other tissues.
This means that blood flow can be reduced in areas that do not need as much oxygen at that time. This can be the case whether you have recently eaten or not.
But let’s say you ate a meal before going to the gym or running.
When we eat, food expands our stomach, resulting in the release of acids and enzymes needed to digest food.
Abdominal muscles also become more active during digestion, leading to increased demand for oxygen and blood flow to the stomach and other gastrointestinal tissues.
Different parts of the autonomic nervous system cause an increase in blood flow to the gastrointestinal structures when they need to be active.
Significant conflicts between different tissues in the body, all of which need oxygen, may be one of the reasons why nausea occurs during or after exercise.
The body must adjust blood flow to the tissues as demand changes.
So, when we exercise, the blood should go to the muscles, heart, lungs and brain, which means that the blood flow is reduced to less active tissues such as the gastrointestinal tract – even while we are digesting dinner.
When blood flow is reduced in this area, it triggers our intestinal nerves, which in turn causes a feeling of nausea.
In addition, the stomach and other abdominal organs can also be compressed during exercise, which can further contribute to the feeling of nausea.
This is a common problem with squats, because the heart rate and the need for oxygen for the tissues increase, so the body draws larger amounts of air into the lungs.
This then causes the diaphragm (below the ribs) to press harder on the abdominal organs.
Other muscles – like those on the abdominal wall – also help, tightening the abdominal organs with each breath even more.
This can lead to significant nausea and even vomiting – even on an empty stomach.
Some evidence even suggests that exercise, especially long-distance running and other resistance training, can damage the lining of the stomach – probably due to reduced blood flow and oxygen available to the organ.
This would also cause nausea. And, in extreme circumstances, it can lead to bleeding from the gastric mucosa, especially in endurance and long-distance athletes.
when to eat
If you exercise immediately or within an hour after a meal, you are more likely to feel nauseous – regardless of the level of exercise or training intensity.
It takes approximately two hours for solid food to break down in the stomach and enter the small intestine; so if you feel nauseous after exercising, it might be best to wait at least two hours after a meal.
What you eat before a workout can also determine if you feel nauseous.
Foods rich in fiber, fatty, and even rich in protein, are all associated with an increased likelihood of nausea after physical activity.
Protein supplements, especially whey or shakes, are also slower to digest. This will probably contribute to nausea during exercise as the stomach tries to digest them.
Certain fats, especially saturated fats, can cause nausea in other ways – animal models show that they irritate and damage the mucous membrane of the gastrointestinal tract, which activates nerves in the gastric mucosa that connect to the so-called vomiting center (located in the medulla). ) in the brain.
Consumption of sports drinks or other high-carbohydrate drinks (such as juices, energy drinks and fizzy drinks) is also associated with nausea during and after exercise.
This may be because these drinks are very slow to digest and stay in the stomach longer than others.
If you often feel nauseous after exercising, there are a few things you can do. First change or reduce your usual workout and slowly increase your intensity.
The longer the workout, the more blood is constantly drawn from the stomach.
Make sure you drink enough water before and after exercising, as too little or too much water can cause nausea for a variety of reasons.
When it comes to diet, avoid eating two hours early and choose the right foods – such as high-quality carbohydrates (such as bananas or sweet potatoes) and protein, as well as unsaturated fats (such as nuts).
Not only will these foods stimulate the body, but they will not be as difficult to digest as others.
* Adam Taylor is Professor and Director of the Center for the Study of Clinical Anatomy at the University of Lancaster, UK.
This article was originally published on the academic page The Conversation and republished here under a Creative Commons license. Read the original version here (in English).
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