Stand with arms extended out in front holding medicine ball or weight plate. Balance on one leg with opposite leg extended straight leg forward as high as possible.
Squat down as far as possible while keeping leg elevated off of floor. Keep supporting knee pointed same direction as foot supporting. Raise body back up to original position until knee and hip of supporting leg is straight. Return and repeat. Continue with opposite leg.
Supporting knee should point same direction as foot throughout movement. Range of motion will be improved with greater leg strength and glute flexibility. Significant spinal flexion occurs at bottom of deep single leg squat to maintain center of gravity over foot. Erector Spinae becomes a stabilizer if spine is kept straight.
An easier, alternative style is to place barbell on back of shoulders and cross lower leg above knee of supporting leg or wrap one foot around back of supporting leg.
Stabilizers (raised leg)
Stabilizers (raised arms)