Leg extension and leg curl machines are two separate pieces of equipment commonly found in gyms that target the muscles in the legs. The leg extension machine is designed to target the quadriceps muscles in the front of the thigh. To use this machine, you sit on the seat with your knees bent and place your ankles behind the padded bar. You then extend your legs to lift the weight, focusing on contracting your quadriceps muscles. The leg curl machine, on the other hand, targets the hamstring muscles at the back of the thigh. To use this machine, you lie face down on the bench with your legs extended and place your ankles under the padded bar. You then curl your legs up towards your buttocks, focusing on contracting your hamstring muscles. Both machines can be used to strengthen and tone the muscles in the legs, and are commonly included in leg workouts to target different muscle groups. It is important to use proper form and technique when using these machines to avoid injury and maximize the effectiveness of the exercise.