Exercise-induced nausea is a feeling of sickness or vomiting which can occur shortly after exercise has stopped as well as during exercise itself. It may be a symptom of either over-exertion during exercise, or from too abruptly ending an exercise session. People engaged in high-intensity exercise such as aerobics and bicycling have reported suffering from exercise-induced nausea. A study of 20 volunteers conducted at Nagoya University, Japan associated a higher degree of exercise-induced nausea after eating.
Lack of hydration during exercise is a well known cause of headache and nausea during exercise. Exercising at a heavy rate causes blood flow to be taken away from the stomach, causing nausea.
Another possible cause of exercise induced nausea is overhydration. Drinking too much water before, during, and/or after extreme exercise (such as a marathon) can cause nausea, diarrhea, confusion, and muscle tremors. Excessive water consumption reduces or dilutes electrolyte levels in the body causing hyponatremia.