Physical Therapy Assistant Practice Exam

Which term describes when a muscle on one side of a joint is stimulated while the muscle on the opposing side is inhibited?

1. Reciprocal inhibition

2. Irradiation

3. Successive induction

4. Rhythmic initiation

The correct answer is: Irradiation

Reciprocal inhibition accurately describes the process where a muscle on one side of a joint (the agonist) is stimulated, leading to the inhibition of the muscle on the opposite side (the antagonist). This mechanism is crucial for coordinated movement and helps prevent opposing muscle groups from contracting simultaneously, which could lead to injury or impede movement. For example, when you contract the biceps muscle to flex the elbow, the triceps muscle on the back of the arm is inhibited, allowing for smooth and controlled motion of the arm. Understanding this concept is pivotal in physical therapy practice, as it informs how therapists facilitate movement and harness muscle activation patterns during rehabilitation exercises. In contrast, the other terms listed do not accurately define this specific neuromuscular phenomenon. Irradiation refers to the spread of muscle activity from a contracting muscle to adjacent muscles, successive induction deals with the sequential activation of muscles, and rhythmic initiation is a technique used in facilitating movement patterns, particularly within neurologically impaired patients. These concepts serve different purposes in the realm of physical therapy and muscle physiology but do not capture the essence of reciprocal inhibition.