Relationship between exercise and sleep

This year, I've taken up kickboxing as a form of exercise. I try to attend about 2-3 sessions per week. The class is pretty intense and most people there are EXTREMELY fit. I'm talking about guys & girls with black belts in karate. They train pretty much everyday. After a kickboxing session, they would run back to the changing room, change into their karate outfits and then join the karate class. On the other hand, I'll be so buggered that all I'll be thinking about is food and water.

Yesterday I had a pretty intense session as I had a 45 minute personal training session which was immediately followed by the usual 1.5 hour class. At the end of it, my hands were trembling so much, I had difficulty typing smses (My hands are still trembling today. I tried to paint earlier but failed pathetically).

That being said, last night, I had the best sleep ever. I immediately fell into dreamland the moment my head touched the pillow. Today is one of those rare days that I woke up feeling extremely fresh despite sleeping for only 6 hours. Good sleep is a rare treat for me as I usually wake up feeling like death has hit me despite sleeping a good 8 hours. I attribute this treat to my intense workout yesterday. Bring it on!