We love this question. 

Per the U.S. Department of Health  “…..regular physical activity substantially reduces the risk of coronary disease, stroke, colon cancer, diabetes and high blood pressure…..and helps to control weight, contributes to healthy bones, muscles and joints….reduces symptoms of anxiety and depression...”  Need we go on?  Cycling is also “low-impact” without the joint stress that you get from “ground-pounding” sports and activities.  It is therefore "soft" on your knees, hips, back and other joints.

Calories burned?  This all depends on the individual and the amount of exertion used.  Cyclists in a spin class working hard can burn from 400-800 calories in a 50 to 55 minute workout such as sessions.