RDL vs. SLDL: What’s the Difference?
In this article, I’ll discuss the main differences between the two exercises, how I coach the lifts, and when to choose one over the other.
Let’s start with some basic descriptions.
Typically, the Romanian deadlift is performed from the top down: the bar is unracked with a double-overhand or mixed grip and lowered to the desired height, at which point the hips are forcefully extended (pushed forward) to bring the bar back up to its starting position.
A Stiff-Legged deadlift, on the other hand, generally starts from a dead-stop on the floor (as in a conventional deadlift), and involves some degree of lumbar flexion (low-back rounding). The hamstrings and lower back must work together to move the bar from the floor to a standing position.
Right off the bat, we can see that the starting positions differ.
Does that have any effect on the execution and subsequent merit of each exercise? You bet it does.
A Little Bit of Exercise Science
Before we get into the nitty-gritty of it, I want to discuss the two different types of muscular contractions involved in these lifts.
When a muscle shortens against resistance it undergoes concentric muscle action. In this type of contraction, the force generated within the muscle is greater than the resistance placed on it.
Anytime we “lift” a weight, say, on the way up from the bottom of a squat, for example, our muscles must concentrically contract to produce force.
The inverse is true for eccentric contractions, which happen when a muscle lengthens under resistance.
In this scenario, the forces acting upon the muscle are greater than the forces generated within the muscle itself. This is the case in any controlled downward movement, such as lowering a dumbbell in a bicep curl.
It is because of eccentric contractions that we don’t simply allow the dumbbell to accelerate rapidly towards the floor. By controlling the descent, we’re still exerting force, albeit not enough to overcome gravity’s pull.
A Romanian deadlift emphasizes eccentric muscle action in its downward phase.
Because the movement is initiated by lowering the weight, you also get the benefits of stretch-reflex when switching from eccentric to concentric actions.
As a muscle lengthens, its contractile properties are increased, so long as the stretching of the muscle occurs within its physiological limits.
This helps explain why it is easier to rapidly bounce out of the bottom of a squat, as opposed to coming to a full stop before squatting back up.
It is also one of the reasons why most lifters tend to lift heavier in the RDL compared to the SLDL. The stretch-reflex allows us to get an elastic effect at the bottom of the movement, where the muscle is fully lengthened.
Now let’s look into what makes the SLDL such a different lift from its Romanian cousin.
The starting position alone tells us there’s a much greater focus on concentric action here.
Anytime we start a lift from a dead-stop we’re relying on the muscle’s “raw” strength and power, without assistance from the stretch-reflex as seen in the RDL.
The SLDL’s starting position also puts the lifter in a huge mechanical disadvantage compared to the RDL or the conventional deadlift.
In order to keep the hips high and the legs straight, the bar must be kept further away from the legs, which taxes the lower back musculature to a much greater degree than the other variations.
Bottom position of the RDL vs. SLDL. Notice the distance from the bar to the hip joint.
What about knee bend?
This is a topic that’s difficult to generalize, as the amount of knee flexion is dependent on individual body proportions.
You can see in the above picture that my SLDL set-up involves a very similar amount of knee flexion to my RDL bottom position, something that I cannot change due to my anatomy.
However, the RDL does allow for “softer” knees compared to the SLDL.
Moreover, although the SLDL is called stiff or straight-legged deadlift, that doesn’t mean you should actually lock out your knees during the lift, as this puts a lot of stress on the ligaments of the back of the knee.
Instead, aim to have your knees slightly less bent, and your hips at about the same height as your shoulders.
Summing it Up
This may seem like a lot of information, so let’s do a recap.
The Romanian deadlit;
- Starts from the top, employing an eccentric muscle action first
- The eccentric focus allows for greater muscle damage, which can enhance strength and hypertrophy but also lead to more DOMS (delayed onset muscle soreness)
- Has a shorter range of motion
- Hips stay below shoulders
- Targets the hamstrings and glutes, with the spinal erectors stabilizing the movement
- Does not involve any lumbar flexion
The Stiff-Legged Deadlift:
- Starts from a dead-stop (although technically you could also start it from the top, but this typically means more room for faulty technique)
- Focus on concentric muscle action
- The concentric focus allows for better strength development off the floor, which can translate into greater strength gains in the conventional deadlift
- Has a greater range of motion
- Hips and shoulders start from approx. same height
- Targets the hamstrings and spinal erectors
- Involves lumbar flexion
So, Which One Should You Be Programming Into Your Training?
As with most things in fitness and life, it depends. It all comes down to risk versus reward and what exactly you’re trying to achieve with either of these exercises.
While the SLDL is great for developing strength off the floor and targeting the low-back muscles, it also puts the lumbar spine in a very compromised position.
This means it may not be suitable for those with a history of low back disorders or insufficient core stability.
If you’re looking to develop the posterior chain, the Romanian deadlift is the safer bet. Not only does it have more pros than cons compared to the SLDL, it’s also easier to learn and works for virtually any body type, something that can’t be said for the stiff-legged variation.
Furthermore, due to its heavy emphasis on eccentric action, the RDL is better suited for injury-prevention, strength and muscle development, increased flexibility and… well, need I say more?
Although the benefits of both exercises rely on their execution, there are modifications you can make to each to slightly alter their training effect.
For instance, when it comes to the SLDL, I pretty much always coach lifters to elevate the bar so that it sits a couple of inches above the floor.
This accomplishes three things:
- It limits the ROM to hip extension only, effectively eliminating any rounding of the lower back. This makes the lift much easier on the back and transfers more of the load on to the hamstrings.
- It facilitates the set up, especially for taller individuals who lack the hamstring flexibility to sustain a neutral spine at the bottom position.
- It allows the lifter to control the eccentric more than they normally would with a full ROM. Slowly lowering a heavy barbell can be a huge risk of injury to the lower-back and should be performed with caution.
Bar on the floor vs. raised on mats. For someone my height, I either have to flex my lumbar spine or bend my knees more to reach the bar in the top scenario.
I also like to tinker with the RDL by lowering it to pins set at the bottom height, thus decreasing the stretch-reflex and emphasizing concentric action instead.
I’m aware this effectively diminishes the ability to lift heavier weights, but it also forces the lifter to use sound technique and control the eccentric even more to avoid crashing into the pins.
Every body is unique, and for that reason, so should training be.
While the RDL and SLDL are similar in many ways, they also vary tremendously with each having unique benefits and disadvantages.
Choosing one lift over the other is up to your personal preference, anthropometry, goals and injury history. Don’t let any workout template tell you otherwise.