Jennings also said that "iso squat holds are a key intro to bodyweight squats while helping to engage our quads, glutes, hamstrings, and core."
Stand with your feet shoulder-width apart or slightly wider and with your chest tall. Extend your hands straight out in front of you, hold them at chest level, or place them behind your head.
Bend at your knees and hips and press your weight back into your heels with your knees over your ankles, pushing your butt out like you're sitting onto a chair. Keep your chest lifted, and do not let your lower back round.
Squat down as low as you can, still keeping your head and chest lifted.
Jennings said to hold for 15 seconds before standing back up.