Final answer:
Inversion and eversion are complex movements that involve the multiple plane joints among the tarsal bones of the posterior foot. Gravity actually enhances the foot inversion motion. Other factors, such as the strength of the tibialis posterior muscle, can also influence foot inversion.
Step-by-step explanation:
Inversion and eversion are complex movements that involve the multiple plane joints among the tarsal bones of the posterior foot (intertarsal joints) and thus are not motions that take place at the ankle joint. Inversion is the turning of the foot to angle the bottom of the foot toward the midline, while eversion turns the bottom of the foot away from the midline. The foot has a greater range of inversion than eversion motion. These are important motions that help to stabilize the foot when walking or running on an uneven surface and aid in the quick side-to-side changes in direction used during active sports such as basketball, racquetball, or soccer (see Figure 9.13i).
When it comes to the role of gravity in minimizing foot inversion, gravity actually enhances the foot inversion motion. Gravity pulls downward on the leg and foot, causing the foot to naturally rotate and invert. This is most noticeable when standing or walking on an incline, where gravity plays a significant role in foot inversion. However, it's important to note that other factors, such as the strength of the tibialis posterior muscle, can also influence foot inversion.