Adjust leg pad to contact lower shin just above the ankle. Adjust seat back to align knees with pivot point on machine. Sit in good body alignment (abs tight, chest up, back straight). Position legs to keep kneecaps on top. In a controlled motion, extend the knees by bringing feet forward and up just before knee lockout. Contract quad muscles fully without compromising form; avoid any hip movement. While maintaining the controlled motion, return to starting position without setting down the weight or relaxing the muscles.
Here are a few suggested alternative exercises:Ball Leg LungeBall LungeBall Wall SquatBand LungeBand Lying Leg ExtensionBand Standing Leg ExtensionBarbell Bulgarian Split SquatBarbell Lateral LungeDead LiftDumbbell Dead LiftDumbbell Hack SquatDumbbell Lateral LungeDumbbell LungeDumbbell Lunge CrossoverDumbbell Lunge WalkingDumbbell SquatDumbbell Sumo SquatFront SquatHack Front SquatHack SquatLeg Press - MachineLunge - BarbellLunge - Smith MachineLunge BackwardLunge CrossoverLunge DiagonalLunge ForwardSquat - Barbell