Conventional deadlifts and stiff-legged deadlifts are both lower-body compound exercises, meaning they work multiple muscle groups and joints. Although they are fairly similar, there are subtle difference between the two lifts. Each has its merits, and the two lifts achieve different goals.
Conventional Deadlifts
Deadlifts work your posterior chain -- the group of muscles that includes your glutes, hamstrings, lower back and core as well as your upper back and forearms. When pulling in a conventional style, you should stand with your feet shoulder-width apart while holding the bar with your hands shoulder-width apart. Start with your knees bent and hips pushed back, then straighten both as you lift the bar from the floor. Deadlifts are a functional exercise, notes strength coach Nia Shanks, author of the "Lift Like a Girl Guide," as they have carryover to improving strength in everyday life.
Stiff-Legged Deadlifts
Stiff-legged deadlifts work the same muscles as conventional deadlifts but with a varying degree of emphasis. They involve the hamstrings and glutes more than a conventional deadlift, and they put less strain on your lower back. The position of your feet and your grip on the bar should be the same as in a conventional deadlift, but start with the bar elevated in a power rack, and lift it from the pins. Descend toward the floor by pushing your hips back while keeping your back straight. When you're as low as you can go, lift the bar again by pushing your hips forward. Your knees should remain straight throughout the entire movement.
Competition
Conventional deadlifts are part of a powerlifting competition, stiff-legged deadlifts are not. However, according to trainer Eric Cressey, author of "Maximum Strength," stiff-legged deadlifts are an effective ancillary exercise to improve your conventional deadlift. Whether you compete or not, there's no way you can cheat in the execution of a deadlift, according to Shanks -- unlike the bench press where you can use partial range of movement or poor form to limit the benefits of the exercise.
Considerations
Because stiff-legged deadlifts isolate your hamstrings and glutes and don't involve your lower back as much as the conventional deadlift, you should use a lighter weight when performing the stiff-legged version. Strength coach Cassandra Forsythe writes in "The New Rules of Lifting for Women" that you should switch between the type of deadlift you perform. For example, you can perform stiff-legged deadlifts in one four-week training cycle and conventional deadlifts in the next cycle. This methods provides the benefits of both. Keep the number of sets and repetitions low to moderate -- between three and five sets of five to eight reps.
