If a person ran five miles, which muscle would perform the most significant amount of work?

The quadriceps femoris is the primary muscle group responsible for running and performing significant lower-body movements, making it the muscle that performs the most work when a person runs five miles. This muscle group consists of four muscles located at the front of the thigh and plays a crucial role in extending the knee and stabilizing the leg during running.

When running, the quadriceps engage intensely to propel the body forward, absorb impact, and maintain the rhythm of the stride. Their role in dynamic activities like running is essential; without the quadriceps, maintaining speed and effectively pushing off the ground would be difficult.

The other muscles listed do not contribute significantly to the action of running. The sternocleidomastoid primarily assists with neck movements, the biceps are mainly involved in arm flexion, and the pectoralis major is crucial for movements of the shoulder, such as pushing and lifting, but does not play a substantial role in the mechanics of running. This distinction underscores the importance of the quadriceps in lower-body endurance activities.