What would cause throwing up after cardio exercise?

People tend to vomit after working out because of what is called an "Energy imbalance". This happens to people who don't workout for a long time, then one day decide to run a mile. Or people who run a mile everyday and then decide to sprint a mile. Your body gets used to a certain level of activity and when that level is increased all the sudden your body will react like you just got the flu. You will vomit, get dizzy and in some cases get a low grade fever. After you rest your body realized that everything is okay, and will go back to normal.

Just start slow, work your way up and don't over due it.