The Structure & Functions of the Musculoskeletal System (AQA GCSE Physical Education): Model Answers
Explain the role of the agonist and antagonist muscles and types of muscle contractions during the phases of a squat. Include how muscular hypertrophy can impact performance.
The knee is a hinge joint composed of the femur and tibia, with the patella, or kneecap, positioned in front of it [AO1]. During the upward phase of a squat, when extension occurs at the knee joint, the quadriceps group acts as the main agonist, while the hamstring group serves as the antagonist. As the quadriceps contract isotonic concentrically, they pull on a tendon [AO2], which is inelastic [AO1]. This action pulls the tibia, increasing the angle at the joint.
During the downward phase of the squat, as flexion occurs at the knee joint, the quadriceps group remains the agonist. This is because it contracts isotonic eccentrically to control the speed of the downward movement caused by gravity. The hamstring group, once again, acts as the antagonist [AO2].
The larger the quadriceps group, the more force it can generate, allowing the performer to move heavier weights. If the performer engages in weight training, performing 5 sets of 3–6 reps at 80–90% of their one-rep max, muscular hypertrophy will occur, further increasing the weight that can be lifted [AO3].