Which muscle or muscle group is responsible for flexing the tarsus and extending the digits?

The gastrocnemius muscle is primarily responsible for flexing the tarsus (the ankle joint) and extending the digits in animals. This muscle, which is part of the hind limb, works in conjunction with the soleus muscle to allow for plantigrade and digitigrade locomotion, enabling the animal to push off the ground effectively. The gastrocnemius is particularly crucial during activities such as running and jumping, where the flexion of the tarsus and extension of the digits are necessary for propulsion.

In contrast to other muscle groups listed, the stifle flexors are more involved in actions related to the knee joint, the quadriceps mainly extend the stifle joint, and the gluteal group primarily plays a role in hip movement and stabilization. These muscle groups do not directly contribute to the flexing of the tarsus or the extending of the digits in the same way that the gastrocnemius does. Thus, the focus on the gastrocnemius underscores its specific function related to the movements of the tarsus and digits.