At heel contact, the lateral CoP location helps explain the foot's natural tendency toward plantarflexion and what other motion?

At heel contact, the lateral CoP location helps explain the foot's natural tendency toward plantarflexion and what other motion?

• A. Dorsiflexion
• B. Inversion
• C. Adduction
• D. Eversion

Answer: (D)

Focusing on how the ground reaction force interacts with the foot at heel contact helps you see why eversion is the best match. When the center of pressure sits toward the lateral edge of the heel, the ground reaction force vector lies outside the hindfoot’s axis, producing a torque that tends to evert the calcaneus. This lateral loading works with the foot already being in a bit of plantarflexion at heel strike, promoting the rapid pronatory motion you see early in stance. Dorsiflexion would be the opposite ankle motion, so it doesn’t fit with the plantarflexion tendency. Inversion would turn the sole inward, which isn’t driven by a lateral CoP. Adduction is a different plane motion that isn’t the primary response here. The combination of plantarflexion and eversion best explains the observed tendency at heel contact.

Focusing on how the ground reaction force interacts with the foot at heel contact helps you see why eversion is the best match. When the center of pressure sits toward the lateral edge of the heel, the ground reaction force vector lies outside the hindfoot’s axis, producing a torque that tends to evert the calcaneus. This lateral loading works with the foot already being in a bit of plantarflexion at heel strike, promoting the rapid pronatory motion you see early in stance.

Dorsiflexion would be the opposite ankle motion, so it doesn’t fit with the plantarflexion tendency. Inversion would turn the sole inward, which isn’t driven by a lateral CoP. Adduction is a different plane motion that isn’t the primary response here. The combination of plantarflexion and eversion best explains the observed tendency at heel contact.