One way to tell how intensely you're exercising is to perform the

I would say to check your heart rate (sometimes treadmills have a handle grip thing for your heart rate)

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle

A.) just took it and made 100%