Use A Leg Curl Machine To Load The Muscles In The Back Or Posterior Of The Leg, Primarily The Hamstrings. The Leg Extension Machine Has You Straighten Your Leg Against Resistance And Thus Works The Muscles On The Front Or Anterior Of The Leg -- Your Quadriceps. Air Spring Auxiliary Adjust Device, Which Brings More Convenience To Users; Adopt Angle Adjustment Device, More Angles Can Be Chosen, Which Optimizes Users’ Movement Locus.