Which of the following is considered a bio-mechanical term?

Retraction is indeed a biomechanical term that refers to the movement of a body part backward, particularly in relation to anatomical positioning. This term is often used in the context of movement of the scapulae (shoulder blades) or other joints, where a body part is pulled toward the midline of the body or moved posteriorly. Understanding retraction is essential in evaluating and instructing proper posture and movement patterns, especially in strength training and rehabilitation contexts.

In contrast, while the other terms are important in physiology and fitness, they do not fall within the biomechanics scope in the same explicit manner. Circulation pertains to the movement of blood through the cardiovascular system, respiration refers to the process of breathing and gas exchange, and adaptation generally relates to the body's ability to adjust to stressors, which is broader than a specific movement or mechanical action.