Which of the following exercises is not considered a compound exercise?

A seated leg extension is classified as an isolation exercise, focusing primarily on the quadriceps muscle group. In contrast to compound exercises, which engage multiple muscle groups and joints, the seated leg extension primarily targets just one muscle group (the quadriceps) at the knee joint without substantially involving other muscle groups.

On the other hand, the deadlift, bench press, and pull-up are all compound exercises. The deadlift works several major muscle groups, including the hamstrings, glutes, back, and core, by engaging multiple joints throughout the movement. The bench press targets the chest, shoulders, and triceps, while also recruiting stabilizing muscles throughout the body. Similarly, the pull-up engages the back, biceps, and shoulders, making use of multiple muscle groups during the execution of the exercise. Therefore, the seated leg extension stands out as the only option that does not utilize multiple muscle groups, clarifying its classification as an isolation exercise.