I prefer the use of the elliptical over the treadmill any day! The proper use of the elliptical machine allows you to work all the different muscle groups in your body simultaneously. Also if you have bad knees and joints the elliptical can actually help improve those areas because the exercise involves little to no impact. Allowing you to build muscle tissue in those areas without causing more injury. By adding resistance while on the elliptical you can do a cardiovascular exercise while maintaining muscle tissue. This is the secret to muscle toning.