Which muscle is primarily responsible for leg extension during exercises like leg press?

The vastus intermedius is primarily responsible for leg extension during exercises like the leg press. This muscle is one of the four muscles that make up the quadriceps group, which is located at the front of the thigh. The primary function of the quadriceps, including the vastus intermedius, is to extend the knee joint, allowing for activities such as pressing the legs away from a footplate during the leg press exercise.

During the leg press, as you push against the resistance, the contraction of the vastus intermedius contributes significantly to the overall extension of the knee, facilitating the movement. While the rectus femoris and vastus lateralis also play roles in knee extension, the vastus intermedius is positioned directly underneath the rectus femoris and is optimized for maximizing the force translation necessary for effective leg extension in this particular exercise. The gluteus maximus, being primarily a hip extensor, does not contribute directly to knee extension.