How much energy do we waste on exercise, one we dissipate energy while doing exercise, two we consume electricity for exercising by means of equipment, Air conditioning, lights etc. What if we give back that same energy to planet everyday morning. Today we planted 100 trees in our community, around 50 people spent their energy, it was fun and a very good exercise too. And we can do normal domestic chores, cleaning, car wash as part of our exercise, imagine a billion people doing this everyday as part of their exercise. What if running on a mat or cycling generates & stores electricity, there are already equipment of that kind. How much energy can be generated from those who don't exercise, forget about the energy cost involved in medical problems for those who don't exercise.
We may not be able to do this all the time but even 10% useful energy dissipation can give lot more to this planet..