Why do I have trouble sleeping after exercise?

Exercise causing increased metabolism in your body. It released more energy, producing heat and sweating ,your muscles are more active (contracted) and blood supply to organs increased. For sleeping your body needs to be in a relaxed state, relaxation of muscles, low brain funtion level., low metabolic rate....

I don't know why I have trouble sleeping after exercise. Maybe because my body is tired but my brain is still too active which gives me trouble with trying to fall asleep.

Exercise before sleep can cause stress on the body and mind. The stress winds up the body preparing it for action and can cause you to suffer insomnia.

Your body is probably heated up and physically awake after exercise. I have this problem too sometimes. If you don't already, I would recommend doing some stretching or yoga after a workout to help "cool down" from the exercise.

When you exercise, your heart rate increases and the body prepares itself for extended physical activity, so when you immediately lie down afterwards, it can take a while for the body to make adjustments.

Here is my take on this question... You want the room to be dark. You're pineal gland releases a hormone called melatonin as a response to darkness, and it's function is to help you get to sleep. It has antioxidant properties, along with many other functions, but you will be taking it to sleep. There is a fall off in melatonin release by the pituitary with aging, Supplementing this dietary supplement might counteract this? Consult with you're physician first though. This is one of the reasons people have more difficulty sleeping as they get older. So, try the melatonin if you're having trouble. The other thing you can do is to have a cup of herbal tea right before bedtime. And sweeten the tea with either sugar or honey. That's right. Real sugar. A teaspoon of sugar is about 5 grams of carb, which won't do a lot to hinder your weight loss, but it will be enough to shut down ketone production long enough to get you to sleep. And if you think a teaspoon of sugar isn't all that much, remember, it's the total amount circulating in your blood if you have a normal blood sugar.

Because during exercises you inhale and exhale rapidly so you get hyper-oxygenated and so you get energetic. It's like drinking redbull in the middle of the night (do you expect any sleep afterwards?)

After exercise, you'll have high blood pressure, which difficult to relax or sleep. If you force your body to sleep, maybe, at midnight, you could suffer from high headache, caused by the pressure (i felt them). So, relax after exercise and take time before go to bed.

Exercise wakes up your body, try to relax 2 hours before going to bed in order for your body to feel rested

That is because your body is in a "hyped up" stage. It is in full mode and is anticipating more action. That is why after you exercise, drinking a glass of milk can help since it lowers stress levels and helps you relax making it easier to dose off. Another method is to take a warm bath before going to bed.