Final answer:
The main stabilizer of any lower body exercise is the quadriceps, which are essential for knee stability and extension. The triceps brachii is the muscle responsible for extending the forearm.
Step-by-step explanation:
The main stabilizer of any lower body exercise is b) Quadriceps. The quadriceps, located in the front part of the thigh, are critical for knee extension, stability during movement, and are heavily involved in lower body exercises such as squats, lunges, and leg presses. They often work in coordination with other muscles, including the hamstrings, to control movements of the leg and provide stability for the knee joint.
When discussing the forearm, the b) triceps brachii is responsible for extending the forearm. This muscle is the prime mover, or agonist, for this motion, while the biceps brachii acts as the flexor for elbow joint movements. Additionally, the gluteus maximus is an important muscle in the lower body, serving functions similar to the quadriceps but for the hip joint.