Exercise-induced nausea is a fairly common phenomena, even though everyone may not experience it. A lot of anecdotal evidence suggests that for those who do not exercise regularly, nausea and vomiting after exercising are especially common.
According to a December 2013 study published by Przeglad Gastroenterologiczny that focused on a case of a 21-year-old male runner being admitted to the hospital, gastrointestinal complaints are common among physically active individuals. The study points to several different causes of these issues, including dehydration, delayed stomach emptying or hyponatremia. Less commonly, these symptoms are associated with conditions affecting various internal organs.
Vomiting after exercise can develop from dehydration, heat exhaustion, low sodium in the blood or reflux. It can also occur if you're new to a particular exercise.
Dehydration and Vomiting After Exercise
The primary cause for experiencing nausea and vomiting after a workout, particularly if it is strenuous, is dehydration. When you exercise, the effort used in the activity makes you sweat and lose both moisture and salts from your body. Both water and these salts are necessary for maintaining the electrolyte balance in the body. You may feel nauseated when your electrolyte balance is disturbed.
Read more: Dehydration and Water Vs. Gatorade
Heat Exhaustion and Nausea
A lot of heat is generated within the body when you exercise. It is important to cool off for a few seconds between sets of exercises, or as directed by the fitness instructor, or else the body loses vital nutrients as well as moisture. Heat exhaustion is the leading cause of dehydration. When fluids are not replaced inside the body, it results in vomiting and nausea. Strenuous exercise, coupled with hot and humid weather, could further intensify the nausea and vomiting.
Vasovagal Reaction to Exercise
When the body is excited, the heart rate begins to rise rapidly. However, a very small percentage of people experience the opposite effect on their heart rate. As the heart rate slows, blood pressure drops and you experience nausea as well as vomiting after exercise.
Although this is a possible cause for experiencing nausea and vomiting after exercise, this is rather rare. According to Mayo Clinic, vasovagal reactions are usually benign and could be triggered by physical strain, such as exercise.
Low Sodium Levels
Hyponatremia occurs when sodium levels in the blood drop lower than normal. To prevent dehydration, when the body is going through physical strain, the brain activates a chemical known as ADH, which attempts to maintain the electrolyte balance of the body by directing the kidneys to hold on to free water.
If your diet is low in essential minerals and salts, it could lead to a sudden drop in sodium levels after a session of exercise, playing sports or other kinds of physical strain. As the electrolyte balance is disturbed, the body experiences nausea or vomiting after a workout.
Other symptoms of this condition include low energy levels, headache, confusion, muscle cramps or changes in mental status. In severe cases, hyponatremia can lead to seizures or even coma.
Gastroesophageal Acid Reflux
Acid reflux in the body is caused when the esophageal sphincter is weak and the muscle relaxes involuntarily. When this occurs, the bile salts and digestive acids from the stomach rush into the throat, causing anything from a slight regurgitation to full-blown nausea and vomiting after exercise. This acid reflux could also cause damage to the esophageal lining.