ACSM Personal Trainer Certification 2025 – 400 Free Practice Questions to Pass the Exam

The correct answer focuses on the primary muscle group engaged during knee extension, which is the quadriceps. The quadriceps, located at the front of the thigh, consist of four muscles that work collectively to extend the knee joint. When performing exercises targeting knee extension, such as leg presses or knee extensions on a machine, it is primarily the quadriceps that are contracted and strengthened.

In contrast, other options involve muscle groups that are not significantly activated during this particular movement. The glutes are primarily involved in hip extension and movements that require hip stabilization rather than knee extension. The hamstrings, located at the back of the thigh, are responsible for knee flexion and will engage in exercises that bend the knee rather than extend it. Lastly, the biceps are muscles in the upper arm that flex the elbow joint and do not have a considerable role in knee-related movements. Thus, the quadriceps are the key muscles engaged during knee extension exercises.