Stand with shoulder width or narrower stance. Grasp dumbbells to sides.
With knees straight, lower dumbbells to top or sides of feet by bending hips. Allow hips to fall back and bend waist as dumbbell approaches feet. Lift dumbbells by extending hips and waist until standing upright. Pull shoulders back if rounded. Repeat.
Begin with very light weight and add additional weight gradually to allow lower back adequate adaptation. Throughout lift keep arms and knees straight. Keep dumbbells close to legs. Do not pause or bounce at bottom of lift. Lower back may bend slightly during full hip flexion phase. Do not lower weight beyond mild stretch throughout hamstrings and low back. Full range of motion will vary from person to person depending on flexibility. See Dangerous Exercise Essay.