Why do you vomit after an intense exercise?

On our high school crew team the stroke for our boat throws up after almost every race. He is projectile vomiting after every 1500 piece we do. My question is why do people tend to throw up after an intense workout. It usually tends to happen to me in exercises where i need to rely completely off of mental power because i am physically spent. Is this a result of me pushing too hard? And is this unhealthy?