Without an alarm, I tend to sleep 4 hours a day. But this is provided I dont exercise. If I go to workout at a gym / Martial arts, I find I have to sleep 7 hour

Without an alarm, I tend to sleep 4 hours a day. But this is provided I dont exercise. If I go to workout at a gym / Martial arts, I find I have to sleep 7 hours. But both these cases, I do not need an alarm to wake me up. I wake up about 5 minutes before the alarm is going to ring and Stretch in my bed. When the alarm goes I jump off the bed. I actually feel more energized when I sleep for just 4 hours. But I need a 20m nap in the afternoon if this is the case. My schedule is (without exercise) - 10:30 PM to 2:30 AM (with exercise) - 11 PM to 6 AM. I would love to study more about the effects of sleep and how we can control it.