Which of the following best defines the agonist muscle?

The agonist muscle is best defined as the muscle responsible for producing a specific movement at a joint. During an exercise or movement, the agonist contracts to bring about the desired action, such as flexing the elbow or extending the knee. This muscle group is primarily responsible for the action being performed and is often referred to as the "prime mover" because of its direct role in executing the movement.

Understanding the concept of the agonist is crucial for personal trainers as it informs them about how to properly target specific muscles during workouts. For example, during a bicep curl, the biceps brachii is the agonist, actively working to flex the elbow. This knowledge helps in designing effective training programs that focus on strengthening specific muscle groups to improve overall performance and prevent imbalances.