Final answer:
During a back squat, as the gym goer stands up, the quadriceps are under active muscle action and function as the agonists to extend the knee. The antagonistic muscles, like the hamstrings, are not actively contracting but rather serve to balance and stabilize the movement.
Step-by-step explanation:
As the gym brah stands up slowly from his back squat, his quadriceps are under a type of muscle action known as active and they serve as the agonist muscles during this movement. The term 'active' refers to the active contraction of the muscles to generate force, which is required when performing a squat because the muscles must work against gravity to lift the body up.
During the ascent of the squat, the quadriceps work to extend the knee and are considered the prime movers or agonists, meaning they are the primary muscles responsible for the motion of knee extension. Conversely, the hamstrings are relaxed to allow the movement and serve as the antagonists in this scenario; muscles that oppose the action of the agonists but are not actively contracting in a way that would resist the squat movement. The role of antagonistic muscles can also include controlling rapid movement or maintaining body position, essential for balancing and stabilizing the body during such exercises.