Final answer:
Plantar flexors are most active during the propulsion phase of gait, also known as push-off, when they engage in plantar flexion to lift the heel and enable the foot to push off the ground.
Step-by-step explanation:
The plantar flexors are most active during the propulsion phase of gait, also known as the push-off phase, when the heel lifts off the ground and the person is propelling forward on their toes.
During this phase, muscles such as the fibularis longus and the fibularis brevis facilitate plantar flexion by pulling the heel up, allowing the foot to push off the ground effectively.
This action is essential for movements such as jumping, maintaining posture while walking, and even activities as simple as foot-tapping.