The prisoner squat is a lower-body exercise with an emphasis on the quads, hamstrings, and glutes. The exercise also improves upper-body mobility.
Stand in a shoulder-width stance with toes pointed slightly outward. Keeping an upright torso, place your hands behind your head while pulling your shoulders and elbows back.
Lower into a squat position by pushing your hips back and bending your knees until the crease of the hip drops below knee level. Pause at the bottom of the movement, and then extend hips and knees upward, explosively pushing yourself back to the starting position.
Do not round the upper back.
Make sure you drive through your heels and not your toes. Heel should not leave the ground.