No medication or medical formulation is as potent or holds as much promise of better health as a sustained physical activity program. You will live longer and healthier, sleep better, and feel less stressed. In short, running makes living more fun !
And as Edward Stanley said : "Those who think they do not have time for exercise will sooner or later find time to be sick. "
Here you find the Canadian guidelines for physical activity for adults 18 to 64 years.