Final answer:
The question is about the muscle activation sequence in movement, focusing on muscles responsible for flexion and extension in the legs and hips.
Step-by-step explanation:
The student's question appears to be describing the sequence of muscle activation during a specific movement, likely within the context of kinesiology or exercise physiology. Muscles can only contract, they cannot actively extend—this means that for a joint to move, one set of muscles contracts while the other set relaxes back into a non-contracted position. For example, during knee flexion, the hamstrings contract to decrease the angle between the bones of the leg, and during knee extension, the quadriceps femoris contract to increase the angle and straighten the joint. In the hips and thighs, muscles like the gluteus maximus (glut max) and gluteus medius (glut med) have roles in moving the femur and assisting in flexing the thigh, as well as in extending the lower leg when other muscles like the anterior muscles of the femur are involved.