Final answer:
The actions in the posterior compartment of the thigh are moving the lower legs up and back, moving the thigh down and back, and twisting the thigh outward. The quadriceps femoris group acts as an antagonist to the hamstring muscles.
Step-by-step explanation:
The posterior compartment of the thigh includes the hamstring group which is responsible for moving the back of the lower legs up and back toward the buttocks, as when kneeling. These muscles also move the thigh down and back and twist the thigh (and lower leg) outward. The quadriceps femoris group functions as an antagonist to the hamstring muscles.