Shaking after workout (looking for the science behind it)...?

I used to get that too after my longer workouts, and I was worried whether I was doing something wrong. According to my doctor it's just adrenaline pumping through the body: During exercising the adrenaline would push me to do better - get faster and get stronger than my opponent (handball is serious business - losing is not an option :p). When I would stop, the body would still produce adrenaline but I wouldn't use it. Thus there would be some sort of build up throughout the "system" and oxygen would travel too quickly for my body to use it properly... hope that made sense :p