How can you use your personal choices to exercise more safely? A.
not exercising in high-air pollution areas
B.
limiting exercise in hot climates to the early morning and evening
C.
using exercise equipment as it was designed to be used
D.
all of the above

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