During the upward phase of a barbell back squat, what type of contraction do the quadriceps undergo?

During the upward phase of a barbell back squat, the quadriceps muscles undergo a concentric contraction. In this phase, the quadriceps are actively shortening as they generate force to extend the knee joint and lift the body back to a standing position. This contraction is essential for overcoming the load of the barbell and the body's weight, allowing you to return to the starting position.

Concentric contractions are characterized by muscle fibers shortening while producing tension, which is precisely what occurs in the quadriceps during this upward movement. This phase requires the muscles to generate enough force to counteract gravity and lift the load effectively. Understanding the type of contraction involved helps in designing training programs that target specific muscle actions and can play a significant role in improving strength and muscle performance.