What are the secondary muscles used in the machine knee extension?

In the machine knee extension exercise, the primary muscle targeted is the quadriceps, particularly the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Secondary muscles involved include the hip flexors, such as the iliopsoas, which assist in stabilizing the hip joint during the movement. Additionally, the gastrocnemius may engage as a stabilizer, particularly if the exercise is performed with the feet in a specific position. Overall, while the quadriceps are the main focus, these secondary muscles contribute to the overall stability and effectiveness of the exercise.