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.
The primary cause for experiencing nausea and vomiting after a rapid and strenuous workout 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.
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.
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. Although this is a possible cause for experiencing nausea and vomiting after strenuous exercise, this is rather rare. The National Library of Medicine explains that vagal reactions are usually benign and could be triggered by physical strain, such as exercise.
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.
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. This acid reflux could also cause damage to the esophageal lining.