Cycling is a great form of cardio as it gets your heart pumping but is easy on the joints. If you are a regular cyclist you should be aware of which body parts are working, which aren't, and which you need to strengthen and stretch to improve performance. Regardless of whether you clip in or not, the bike stroke utilizes most of the muscles in your lower body, from your hips through your thighs down to your calves. But depending on your bike, seating position and riding style