Final answer:
During a push-up, the muscles at the ankle perform an isometric contraction to maintain a stable position, with no significant motion of dorsiflexion or plantar flexion.
Step-by-step explanation:
When lowering during the push-up, the muscles at the ankle are undergoing an isometric contraction. There is no notable motion of dorsiflexion and plantar flexion as the goal is to sustain a stable position of the ankle throughout the movement.
An isometric contraction is where the muscle generates force without any external movement, effectively maintaining the position against gravity. This contrasts with isotonic contractions, such as concentric and eccentric contractions, where the muscle changes length while moving a load.
During a push-up, even though the arms and chest muscles go through a range of motion, muscles at the ankle support a stable position, hence they remain isometrically contracted.
Therefore, the type of contraction occurring at the muscles activating at the ankle is isometric. In an isometric contraction, the muscle produces tension without changing the length or angle of the joint it acts upon.