Workout (1.5 hrs, 1 muscle/day) in morning (with protein supplements and protein rich diet) leads to insomnia. Any explanations/suggestions?

Working out. I'm not sure how it's possible to work out using only 1 muscle per day? I wonder what the contents of your protein supplement actually are -- some contain stimulating substances, which of course could lead to insomnia. Would also need to know what other medications, supplements, or drugs you might be taking. Do you drink caffeinated beverages?