The phrase "used every muscle" implies using one's entire body, and can be expressed in a variety of synonyms. Some alternatives include "exerted every fiber," "strained all sinews," "extended to the limit," "employed full force," or "maximized physical effort." These phrases emphasize the intensity and dedication of the physical exertion, conveying the belief that every ounce of strength was put into the task at hand. Other possible synonyms might include "pulled out all the stops," "left nothing in the tank," or "went all out." Each of these expressions conveys a sense of complete commitment, implying that the effort expended was neither haphazard nor half-hearted.