The stiff-legged deadlift is a common exercise—and a controversial one. Bodybuilders use it to improve their hamstring development, powerlifters to enhance their deadlift and other athletes to increase hamstring strength.

Before you attempt to do stiff legs, though, you must consider several factors. The first is whether you have a lower-back injury or have suffered one in the past. If you have an injury, don’t attempt the stiff-legged deadlift. No possible gain is worth the risk of reinjury or complications. If you haven’t had any major back problems, then a simple screening procedure may save your back.

The main reason people hurt themselves while performing this exercise is very simple and predictable: They do them while standing on a flat bench. The rationale for standing on a bench is that the bar rests on the bench just in front of your toes, which allows for a maximum range of motion. Otherwise, the height of the 45-pound plates prevents you from achieving the last several inches of your range of motion because the plates touch the floor before you complete the movement.

Standing on a bench does, in fact, increase your range of motion by several inches; however, if you can’t pass the following screening test, it could be hazardous to your health. Bend over in a touch-your-toes effort, but try placing your palms flat on the floor. If you can’t do it, then you’re not physically capable of performing the stiff-legged deadlift on a bench. If you can’t even touch your toes, you have no business whatsoever even thinking about trying it.

If you attempt the movement from a bench, the weight of the bar will force a range of motion that you don’t have. Something will have to give, and it’s most likely going to be your back, or at the very least your hamstring, which could tear.

If you have only average flexibility (and a relatively healthy back), you can safely perform a version of the stiff-legged deadlift. In fact, there are three different methods for working up to a full range of motion. Use the toe-touch test to determine where you should start in the progression. See how far you can stretch without forcing, bouncing or rounding your back excessively.

If you can get your hands only a few inches past your knees, begin with 45-pound plates on each side of the bar, with the bar resting on the floor. Forget about standing on the bench for a while. If your strength level isn’t up to the 135-pound deadlift (two 45-pound plates plus the 45-pound bar), use the power rack, choose a weight that you can handle, and set the pins to the appropriate height for your flexibility. That way you can still make gains without pushing your back beyond its limits.

If your flexibility lets you stretch a little farther than a few inches past your knees but you still can’t touch your toes, use the 35-pound plates instead of the 45s, starting with the bar on the floor. Because the 35s are smaller, you’ll be able to stretch a little farther. Obviously, if you want to increase the weight, you just add more plates that are 35 pounds or less.

If your flexibility is at the toe-touching level, you may want to find a short wooden block to stand on while you do stiff-legged deadlifts. The little bit of height will let you approximate the range of motion while you’re using either 35- or 45-pound plates.

Once you’ve improved your flexibility and can put your palms on the floor, you can do stiff-legged deadlifts while standing on a bench.

Another important consideration in performing the movement safely is the path that the bar travels. When the bar’s path is close to your legs, it reduces the stress on your back. If you’re standing on a bench, the bar will be out away from your toes—even farther from your legs—at the starting point. So as soon as you lift the bar above your feet, bring it close to your legs. Don’t hold the bar away from your body while it’s traveling upward.

Also, do not suddenly accelerate this movement. The additional torque could injure your lower back or hamstrings. You don’t have to keep your lower back rigid or flat during the exercise (the flat-back version is known as the Romanian deadlift), and you shouldn’t round your back excessively during the lower half of the movement, although a little rounding of the back is safe. Don’t thrust your hips forward at the completion of the lift; that causes hyperextension of the lower back, which can lead to further complications. Needless to say, it’s mandatory that you stretch your hamstrings four to five days per week to enhance your flexibility and maintain a healthy lower back.

Because it’s a highly specialized lift, you shouldn’t attempt it with poor technique, poor flexibility, too much weight or inadequate warmup. Lay off it, too, if you have a “bad” or “tricky” back. If you can do it safely, however, you’ll achieve greater hamstring development than you ever had before, and you’ll improve your lower-back development. Just be cautious and be honest with yourself about your limitations.