Physical Therapy Assistant Practice Exam

When is the middle trapezius most active?

1. During shoulder flexion

2. In arm extension or pulling activities

3. When abducting the humerus

4. During lateral arm raises

The correct answer is: In arm extension or pulling activities

The middle trapezius is primarily responsible for the retraction of the scapula, which involves pulling the shoulder blades together. This muscle is most active during arm extension or pulling activities where the shoulder is brought back toward the body. During these actions, the middle trapezius assists in stabilizing the scapula and providing proper positioning for efficient movement and force generation. When engaging in arm extension or activities like rowing or pulling weights towards the body, the middle trapezius works effectively in conjunction with other muscles around the shoulder girdle. This activation is crucial for maintaining good posture and shoulder mechanics. Other activities listed such as shoulder flexion or lateral arm raises do not engage the middle trapezius to the same extent because they primarily focus on different muscle groups like the deltoids and the anterior and upper trapezius. Meanwhile, abduction of the humerus primarily involves the upper trapezius and the deltoid, rather than the middle trapezius, which is more engaged in movements that require scapular retraction.