hyperextensions can be intesified though... instead of putting your ankles under the back pads, put your calves under the back pads. this takes more stress off your knee joints and focuses more on the lower back. I have double jointed knees so with heavy weights my knee joints take a pounding during hyperextenstions. so instead i hold onto plates to make up for the difference and stop and squeeze for a full 2 second count at the top. 3 sets of these and your lower back will be so pumped you'll feel the giant canyon.