What type of muscle contraction is used in preparation for push-off at the ankle during heel off?

The correct choice is the concentric contraction, which plays a crucial role during the preparation for push-off at the ankle during the heel-off phase of gait. At this stage, the ankle undergoes a movement where the calf muscles, primarily the gastrocnemius and soleus, contract to elevate the heel and propel the foot forward.

In a concentric contraction, the muscles shorten while generating force, allowing for the upward movement of the body in preparation for the subsequent push-off. This is essential for generating the necessary force to lift the body and move it forward effectively.

While other types of contractions exist, they are not appropriate for this specific phase of gait. Eccentric contractions occur when muscles lengthen under tension, typically as a muscle controls a movement. Isometric contractions, on the other hand, involve muscle activation without any change in muscle length, which does not contribute to the propulsive action needed during heel-off. Isotonic contractions encompass both concentric and eccentric phases, but the term itself does not specify which type of muscle action is occurring at heel-off. Thus, concentric contraction specifically is what drives the push-off at the ankle, making it the most relevant choice in this context.