Final answer:
The normal active range of motion for ankle plantar flexion is 20 to 50 degrees, which is a movement where the heel is lifted off the ground or the toes are pointed downward.
Step-by-step explanation:
The normal active range of motion (ROM) for ankle plantar flexion is typically between 20 to 50 degrees. During plantar flexion, an individual lifts the heel off the ground, or points the toes downward, which decreases the angle between the front of the foot and the shin.
This range of motion is essential for activities such as walking, running, and jumping, enabling the push-off phase that propels the body forward. In contrast, dorsiflexion is the movement where the top of the foot is lifted towards the anterior leg, increasing the angle between the foot and shin.
Anatomical motions that involve increasing or decreasing the angle of the foot at the ankle joint include dorsiflexion and plantar flexion, as opposed to inversion and eversion which involve the intertarsal joints of the foot and do not occur at the ankle joint.