A wall sit is an isometric exercise, which means it works in a static position—you don’t have to move, you just have to hold it. “Isometric exercises build strength over the duration of the hold, the longer the hold the greater increase of muscle fiber activation and strength,” explains Tim Hartwig, C.S.C.S., a trainer based in Los Angeles..
In my experience, the first thing I felt during wall sits was my quads. But, while a wall sit is a quad-dominant exercise, as Hoebel mentioned, I also noticed it fired up other muscles in my lower body, including calves, hamstrings, and glutes. There were times I even felt it in my abs! The first 10 or 20 seconds felt pretty easy; but the longer I held the position, the harder it felt.
