Romanian deadlift (RDL) vs stiff leg deadlift: what's the difference

Strip away the gym arguments and only two things separate these lifts. The first is knee bend. The RDL holds a soft, consistent bend in the knees throughout the movement. The stiff leg deadlift keeps the legs much straighter, with only a slight unlock so you do not lock the joint out hard.

The second is where the bar starts and stops. A true RDL is a top down lift: you begin standing and lower the bar to about shin height, never letting it touch the floor, so tension stays on the muscles the whole set. A stiff leg deadlift more often starts and resets from the floor each rep, giving a longer range but a brief release of tension at the bottom.

Neither column is the correct lift. They are two points on the same hinge, tuned differently. The RDL trades a little range for control and back safety. The stiff leg deadlift trades some of that safety for a deeper hamstring stretch and a longer pull.

Both are hip hinges, so both hammer the hamstrings and glutes. The 2020 systematic review in PLoS ONE that pooled the deadlift electromyography research found the RDL is a strong driver of the biceps femoris and semitendinosus, the outer and inner hamstrings, with the glutes assisting. The stiff leg version, because the straighter legs force the torso further forward, tends to bias slightly more toward hamstring stretch and lower back involvement.

The practical read: if your goal is well loaded hamstrings and glutes with a back friendly setup, the RDL delivers almost all of it. If you specifically want to overload the hamstrings in a deep stretch and you have the flexibility and a healthy back, the stiff leg deadlift adds a little more of that at the cost of more spinal demand.

For most people, most of the time, the RDL is the smarter default. It gives you the vast majority of the hamstring and glute benefit with more control and less demand on your lower back. It is also easier to load heavily and safely, which matters for long term progress.

1. Start with the RDL if you are unsure. It teaches the hinge, keeps constant tension, and is forgiving on the back. Most lifters never need anything else for hamstrings and glutes.
2. Add the stiff leg deadlift only when the hinge is solid. Once you can hold a flat back through a full RDL, the straighter legged version is a useful way to push hamstring stretch and range.
3. Match the lift to your flexibility. If you cannot reach much depth without your back rounding, the stiff leg deadlift is not for you yet. Build range with RDLs first.
4. Keep the bar close on both. Whatever the knee angle, drag the bar down your legs so the load stays over your hips and off your spine.
5. Do not chase the floor. On either lift, the moment your lower back rounds to reach lower, you have gone past your useful range. Stop at your stretch.