Many of us train to become better after a workout. However, some of us abandon the gym feeling nauseous. Although this technique is usually only temporary, it may be difficult to maintain.
Fortunately, there are a few good explanations for why this may occur, so if this happens to you there is likely no reason to be worried.
When we exercise, there''s an increase in blood flow to the working muscles, brain, lungs, and heart.
This increase in blood flow is aided by the sympathetic part of the autonomic nervous system (which helps regulate all of our involuntary body responses, such as heart rate, blood pressure, and digestion). It does this by widening the arteries so that they may transmit more blood to these tissues.
During a difficult exercise, the sympathetic nervous system, which is usually responsible for our "fight or flight" system, narrows the blood vessels entering our digestive system (such as our stomach) by up to 80 percent.
It does this because there is a limited amount of blood in the body, and the increased oxygen demand by several tissues cannot only be reduced by altering the amount of blood that is being transferred to other tissues.
This means that blood supply may be reduced in areas that do not currently require as much oxygen at that time. It may be the case whether or not you''ve recently eaten.
Let''s say you''ve recently ate a meal before going to the gym or taking a walk. When we eat, the food breaks our stomach, resulting in the release of acids and enzymes needed to digest the food.
During digestion, the stomach muscles gain greater demand for oxygen and blood flow to the stomach and other gastrointestinal tissues. A different part of the autonomic nervous system causes blood flow to increase to the gastrointestinal structures when they need to be active.
The significant conflict in the body from different tissues, all of which require oxygen may be one reason why nausea occurs during or after a workout. The body must adapt the blood flow to the tissues as demand changes.
So, when we work out, blood must go to the muscles, the heart, the lungs, and the brain, resulting in reduced blood flow in less active tissues, such as the gastrointestinal tract even if it''s currently digesting our dinner. It also causes our intestinal nerves to subside, which subsequently causes sensations of pain.
On the back, the stomach and other abdominal organs can be reduced during exercise, which may result in sensations of fatigue. This is especially an issue in squatting, as the heart rate and oxygen demand in tissues increase, and so the body draws larger volumes of air into the lungs.
This causes the diaphragm (under your ribs) to push down harder on the abdominal organs. Other muscles such as those in the abdominal wall also assist, further squeezing the abdominal organs with every breath. This can result in significant nausea and even vomiting even on an empty stomach.
Exercise, particularly long distance running and other endurance events, may sabotage the stomach lining, due to the decrease in blood flow and oxygen that is available to the body. This would also result in a nausea.
In extreme circumstances this may result in bleeding of the stomach lining, particularly in endurance and long distance athletes.
When to eat
Regardless of your exercise level or workout intensity, you''re likely to experience nausea once or twice as fast as you have ate.
It takes approximately two hours for solid food to be broken down by the stomach and enter the small intestines, so if you feel nausea after workouts, it may be best to wait at least two hours after a meal.
What you eat before a workout may determine whether or not you experience nausea. All of these fibers, fat, and even high protein foods are linked to a greater risk of nausea following a workout.
Supplemental protein, particularly whey or shakes, is also digested more slowly. This is likely to cause nausea during a workout as the stomach attempts to digest it.
Animal methods show that certain foods, particularly saturated, may induce nausea differently, causing discomfort and inflammation of the stomach tract, which activates nerves in the stomach lining that connect to the vomiting center (located in the medulla oblongata) in the brain.
Sports drinks or other high-carbohydrate beverages (such as juices, energy drinks, and sodas) are also linked to nausea during and after a workout. This may be because these drinks are very digested slowly and stay in the stomach longer than other beverages might.
If you''re someone who experiences nausea after a workout, here are a few things you can do. First, modify or reduce your usual exercise, and increase intensity slowly. This is because the longer the workout, the more blood is always drawn away from the stomach.
Make sure you get enough water before and after a workout, because too little and too much can cause gastrointestinal upset for various reasons.
Avoid eating them two hours before and choose the appropriate dietary supplement, such as high-quality carbohydrates (such as bananas or sweet potatoes) and protein, as well as unsaturated fats (such as nuts). These can not only feed the body, but they will not be as difficult to digest as other foods if you plan to work out.
Adam Taylor, Professor and Director of the Lancaster University Clinical Anatomy Learning Centre, is a graduate student.
This article has been republished from The Conversation under a Creative Commons license.