Plantarflexion - refers to the movement of the foot in a downward motion away from the body.
Dorsiflexion - refers to the raising of the foot upward towards your shin.
Plantarflexion is the same movement that allows a ballet dancer to stand on their toes. Ankle flexibility is an important factor in a swimmers kick. Dr. Caitlin Glenn Sapp says, "Joint mobility and muscle flexibility at the ankle play a vital role in the mechanics needed for a proper swim kick. If you’re missing these essential ankle mechanics, you’re more likely to experience the infamous calf cramp. A lack of plantarflexion, or the ability to point foot and toes downward, makes ankles act as anchors. Without the ankles doing their job, you’ll have to work more from the knees and hips, causing a less efficient kick because you’re placing a higher workload on your body."
Reasons You Might Not Have Proper Plantarflexion
Poor mobility through the ankle joint due to injury or preexisting condition such as arthritis.
Lack of tissue length and flexibility of the gastrocnemius and soleus (calf muscles).
Sapp concludes, 'Compared to other muscles, the calf muscles has a larger than normal amount of Type II fast-twitch muscle fibers, meaning the muscle is most efficient for short, anaerobic efforts. If this muscle is in a contracted state for a prolonged period to make up for lack of plantarflexion, cramping in the calf will likely occur.'