Final answer:
Active trigger points in the extensor digitorum longus muscle can lead to pain when walking and calf cramps at night. This muscle assists in dorsiflexion and toe extension. correct option is D.
Step-by-step explanation:
The student's question refers to pain while walking and nocturnal calf cramps potentially caused by active trigger points in the extensor digitorum longus muscle. This muscle, located in the anterior compartment of the leg, plays a significant role in foot movements. Specifically, it aids in dorsiflexion, or the raising of the front part of the foot, and extends the toes.
During a withdrawal reflex, such as stepping on a sharp object, the body exhibits a protective response. Painful stimuli received by nociceptors can cause the activation of motor neurons controlling the tibialis anterior muscle, which is responsible for pulling the foot away from harm through dorsiflexion. Simultaneously, inhibitory interneurons work to inhibit the muscles at the back of the leg, namely the gastrocnemius and soleus muscles associated with the Achilles tendon, which would otherwise perform plantar flexion — pushing the foot down further onto the object. This coordination helps avoid further injury when encountering a painful stimulus.
When discussing the forces on the Achilles tendon produced by the muscles in the back of the leg, particularly the gastrocnemius muscles during toe standing, it illustrates the pulling action that contributes to plantar flexion. In contrast, the muscles in the anterior compartment, including the extensor digitorum longus, counteract this by enabling dorsiflexion.