Largest human muscle, informally

GLUTE

Think of what you sit on—it’s the powerhouse behind squats and sprints.

This clue plays on the informal name for the gluteus maximus, which is the largest muscle in the human body. "Glute" is a common shorthand for it, often used in fitness or casual conversation. The word "informally" signals that the answer isn’t the full scientific term but the shortened, everyday version.