The solution to being able to exercise on mars - We will be able to exercise and stay on fit so we can get used to the gravity there and when were working really hard you would get used to the gravity and won't be weak so that's why you would need to exercise to live so you can get used to the gravity. There would be treadmills that are sideways so you can get used to it.
Credit for the original videos goes to https://www.youtube.com/watch?v=JLUiJW3YPhs