You can easily modify this by doing it with bent knees, or simply holding a bent knee position without going up and down. (thebettyrocker.com)
Lower your hips so that your right thigh (front leg) becomes parallel to the floor with your right knee positioned directly over your ankle. (yurielkaim.com)
Be sure to keep your front knee positioned over your ankle to keep this move safe! (fitbodyhq.com)