Final answer:
A ground reaction force placed anterior to the ankle joint will create B) an ankle plantar flexion moment, causing the heel to lift as the toes point down. The opposite force applied posteriorly would lead to an ankle dorsiflexion moment.
Step-by-step explanation:
If a ground reaction force occurs anterior (in front) to the ankle joint, this results in B) an ankle plantar flexion moment.
This happens because the force would push the top of the foot downwards, causing the heel to lift as the toes point downward, exactly what occurs during plantar flexion.
On the contrary, an ankle dorsiflexion moment would be created if the force were applied posterior to the ankle joint, which would lift the front of the foot upwards and bring the top towards the shin (anterior leg).
It is important to note that the creation of these moments can stimulate contraction of the muscles around the joint to balance the body and stabilize the ankle.
The gastrocnemius and soleus muscles, which connect to the Achilles tendon, are primarily responsible for plantar flexion.
Alternatively, the tibialis anterior muscle on the front of the leg is one of the main muscles involved in dorsiflexion.