Final answer:
Overactive hip flexors can lead to an excessive forward trunk lean during an overhead squat assessment, as they are responsible for bringing the thigh and trunk closer together.
Step-by-step explanation:
During an overhead squat assessment, if a student exhibits an excessive forward trunk lean, one possible cause could be overactive hip flexors.
The hip flexors are a muscle group responsible for pulling the thigh and trunk towards each other, and when they are overactive or tight, they can cause the trunk to lean forward as the body tries to descend into a squat.
It's important to differentiate this from gastrocnemius and soleus, which are muscles in the calf involved in plantarflexion of the foot, and the gluteus medius, which is a muscle in the hip involved in abduction and internal rotation of the thigh.