Physical Therapy Assistant Practice Exam

What role do the quadriceps play during an eccentric contraction?

1. They assist in movement acceleration

2. They control movement while lengthening

3. They stabilize against joint extension

4. They initiate movement from a stationary position

The correct answer is: They control movement while lengthening

The role of the quadriceps during an eccentric contraction is to control movement while lengthening. In this type of muscle contraction, the quadriceps are actively engaged as they lengthen to gradually counteract forces that would otherwise cause a rapid descent, such as in activities like lowering oneself into a chair or during the down phase of a squat. Eccentric contractions occur when a muscle is generating force while being elongated, which is critical for controlling movements in a controlled manner. This function of the quadriceps helps to manage the speed of descent and provides stability to the knee joint, preventing uncontrolled joint motion and potential injury. In contrast, other options pertain to different aspects of muscle function that do not specifically relate to the nature of eccentric contraction. For example, assisting in movement acceleration pertains more to concentric contractions where muscles shorten to produce movement, while stabilizing against joint extension primarily implies a static role rather than the dynamic control seen in eccentric actions. Initiating movement from a stationary position would also involve concentric contraction mechanics rather than the lengthening of the muscle. Thus, understanding the quadriceps' role as lengthening under load highlights their crucial functionality during eccentric contractions.