ACSM Personal Trainer Certification Practice Exam

Which muscle works in conjunction with the soleus during plantarflexion?

1. Gluteus maximus

2. Quadriceps

3. Gastrocnemius

4. Iliopsoas

The correct answer is: Gastrocnemius

The gastrocnemius is crucial for plantarflexion, which is the movement of pointing the toes or elevating the heel, commonly seen in actions like standing on tiptoes or pushing off during walking and running. This muscle is a powerful contributor to this movement, working alongside the soleus. While the soleus is primarily responsible for stabilizing and controlling the ankle position during plantarflexion, the gastrocnemius assists in generating more force during this action, especially when the knee is extended. It is important to note that the gastrocnemius is a two-joint muscle; it crosses both the knee and ankle joints. Therefore, its contribution to plantarflexion increases significantly when the knee is straight, as opposed to when it is flexed. The gluteus maximus, quadriceps, and iliopsoas are not directly involved in this action of the ankle joint, making them less relevant options in relation to plantarflexion.