Which muscle is primarily responsible for plantar flexion of the foot at the ankle?

• A. Gastrocnemius
• B. Fibularis (peroneus) longus
• C. Tibialis posterior
• D. Tibialis anterior

Answer: (A)

Verified step by step guidance

1. Understand the movement described: plantar flexion of the foot at the ankle refers to pointing the toes downward, like pressing a gas pedal.
2. Recall the major muscles involved in ankle movements, focusing on those that cause plantar flexion.
3. Identify the Gastrocnemius muscle, which is a large calf muscle crossing the back of the knee and ankle, known for powerful plantar flexion.
4. Consider the other options: Fibularis (peroneus) longus mainly everts the foot, Tibialis posterior assists in inversion and plantar flexion but is not the primary mover, and Tibialis anterior is responsible for dorsiflexion (lifting the foot upwards).
5. Conclude that the Gastrocnemius is the primary muscle responsible for plantar flexion at the ankle due to its size, position, and function.