Romanian Deadlift vs Stiff Leg Deadlift

The 1-Inch Bar Path Difference That Changes Everything

The core difference in the Romanian deadlift vs stiff leg deadlift debate is a 1-inch bar path deviation and a fixed 15-degree knee bend. This small change completely shifts the target from your hamstrings and glutes to your lower back and spinal erectors. You've likely seen both lifts in programs, noticed they look almost identical, and are worried you're doing the wrong one for your goals. Worse, you might be doing a sloppy hybrid of the two and feeling it all in your lower back, which is the fastest way to get frustrated and quit.

Let's clear this up for good. 90% of people reading this should be doing the Romanian Deadlift (RDL). It is the superior movement for building muscle in your hamstrings and glutes.

Romanian Deadlift (RDL): The Hamstring Builder

This is a pure hip hinge. You initiate the movement by pushing your hips straight back. Your shins stay almost perfectly vertical, and your knees maintain a soft, fixed bend of about 15-20 degrees throughout the entire lift. The barbell slides down your thighs, staying as close to your body as possible. The goal is to load the hamstrings and glutes through a deep stretch. Think of it as a horizontal movement: hips back, then hips forward.

Stiff Leg Deadlift (SLDL): The Back Strengthener

This is a spinal flexion and extension movement. While your legs are kept 'stiff', they are not locked out. You initiate by bending at the waist, allowing your lower back to round as you lower the bar. The bar drifts a few inches out in front of your legs, creating a massive lever arm that your lower back (spinal erectors) must control. This is not a primary muscle-building exercise; it's a specific accessory movement for strengthening the lower back and providing a loaded stretch for the entire posterior chain. It's a tool for advanced lifters, not a foundation for beginners.

If your goal is a stronger, more muscular lower body, the RDL is your answer. If you're an advanced powerlifter looking to strengthen your spinal erectors to support a heavier conventional deadlift, the SLDL has a place, but with much lighter weight.

Why One Lift Builds Your Hamstrings and the Other Risks Your Back

The reason an RDL targets your hamstrings and an SLDL targets your lower back comes down to one simple physics concept: the moment arm. The moment arm is the distance from the joint doing the work to the weight being lifted. A longer moment arm means the muscle has to work exponentially harder.

In a Romanian Deadlift, you keep the barbell glued to your legs. This creates a very short moment arm for your spine, meaning your lower back only has to work to stay stable. However, because you're pushing your hips far back, you create a long moment arm for your hip joint. This forces your hamstrings and glutes-the primary hip extensors-to do the vast majority of the work to pull the weight back up. This is exactly what you want for building muscle in those areas.

In a Stiff Leg Deadlift, the opposite happens. As you bend over, you intentionally let the bar drift a few inches forward. This small change dramatically increases the length of the moment arm for your spine. Your lower back muscles now have to fight immense leverage to control the weight. Think about holding a 45-pound plate. Holding it against your chest is easy. Holding it with your arms extended straight out is brutally difficult. That's the difference in force your spine experiences between an RDL and an SLDL.

This is why the #1 mistake people make is using their RDL weight for an SLDL. They treat it like a primary lift when it's an accessory. An SLDL should be performed with 40-50% less weight than your RDL. Trying to go heavy on an SLDL puts your spinal discs under tremendous shearing force and is a recipe for injury, not growth.

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Your 4-Step Checklist for a Perfect Hinge

Executing these lifts correctly is non-negotiable. One builds muscle safely; the other can sideline you if you're careless. Follow this checklist precisely. Don't mix and match steps. They are two distinct movements with two distinct purposes.

Step 1: The Setup

The starting position dictates the entire lift. Get this wrong, and you'll be fighting your body the whole time.

• RDL Setup: Start from a standing position. Unrack the barbell from a squat rack set to mid-thigh height. Your feet should be about shoulder-width apart, toes pointing forward. Take one step back, pull your shoulders back and down, and engage your lats to keep the bar close.
• SLDL Setup: This lift traditionally starts from the floor. To increase the range of motion and get a better stretch, stand on a small platform or a 45-pound plate (1-2 inches of elevation). Your feet should be narrower, about hip-width apart.

Step 2: The Descent (The Money Phase)

This is where the magic happens for the RDL and where the risk appears for the SLDL.

• RDL Descent: Unlock your knees to a 15-20 degree bend. Now, *freeze them there*. The rest of the movement comes from your hips. Push your butt straight back as if trying to touch a wall 3 feet behind you. Keep your chest up and your back flat. The bar should graze your thighs the entire way down. Stop when the bar is just below your kneecaps or when you feel a powerful stretch in your hamstrings-whichever comes first. Do not let your back round.
• SLDL Descent: Keep your legs as straight as you can without locking your knees. Initiate by bending at the waist. As you lower the bar, allow your back to round naturally. The bar will travel down and slightly forward, away from your shins. The goal is to achieve the deepest stretch possible through your hamstrings and lower back. Control the descent; don't just drop into it.

Step 3: The Ascent

How you return to the start is just as important as how you went down.

• RDL Ascent: Once you hit the bottom of the movement, drive your hips forward with force. Think of it as a powerful thrust. Squeeze your glutes hard at the top to finish the movement. The entire lift is a horizontal push/pull from the hips.
• SLDL Ascent: From the bottom stretched position, think about 'unfolding' your body. Squeeze your hamstrings and lower back simultaneously to pull the weight up. Stand tall, but do not hyperextend your back at the top.

Step 4: Programming for Your Actual Goal

Don't just do an exercise; use it with purpose.

• For Hamstring & Glute Growth (90% of people): Program RDLs as a primary accessory on your leg day. Perform 3-4 sets of 8-12 reps. Choose a weight that brings you within 1-2 reps of failure on the last set while maintaining perfect form. An average man might work with 135-185 lbs, and an average woman with 65-115 lbs.
• For Lower Back Strength & Mobility (10% of people): Program SLDLs as a secondary accessory, preferably after your main deadlifts or squats. Use very light weight. Perform 2-3 sets of 10-15 reps. The focus is 100% on control and the stretch, not the weight on the bar. This is about endurance and mobility, not brute strength.

What Your Hamstrings Will Feel Like in 4 Weeks

Starting a new, effective movement comes with an adaptation period. Here’s the honest timeline so you know what to expect and don't think you're doing something wrong.

Week 1-2: The Soreness Phase

If you perform RDLs correctly for the first time, you will experience a level of hamstring soreness you didn't know was possible. It's a deep, specific ache that confirms you've finally targeted the muscle correctly. Don't be a hero. Start with just the 45lb barbell or very light dumbbells to master the hip hinge. For SLDLs, your lower back will feel fatigued and pumped, but you should not feel any sharp, localized pain. If you do, your form is wrong or the weight is too heavy.

Month 1: The Connection Phase

By week 3 or 4, the debilitating soreness will subside into a satisfying muscle ache. You will have developed a strong mind-muscle connection. You'll be able to feel your hamstrings and glutes working during every rep of an RDL. You should be able to increase your working weight by 10-20% from where you started. You'll also notice your glutes feel more engaged during other lifts like squats.

When to Choose the RDL: Choose the RDL if your goal is building bigger hamstrings, stronger glutes, improving your squat and deadlift, or increasing your athletic power. It is a foundational movement for almost every training goal.

When to Choose the SLDL: Choose the SLDL only if you are an intermediate or advanced lifter with no history of back pain, and you have a specific need to strengthen your spinal erectors for a heavier conventional deadlift. It is a specialist's tool, not a general-purpose builder. For most, the risk outweighs the reward.

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Frequently Asked Questions

Can You Do Both RDL and SLDL in the Same Workout?

Yes, but in a specific order. Perform your heavier, muscle-building RDLs first for 3-4 sets in the 8-12 rep range. Afterwards, you can use the SLDL with a much lighter weight (around 50% of your RDL weight) for 2 sets of 12-15 reps as a loaded stretch and finisher.

The Correct Weight to Use for Each Lift

For RDLs, use a challenging weight that allows perfect form for 8-12 reps. You should feel like you only have 1-2 reps left in the tank at the end of your set. For SLDLs, the weight is secondary to the stretch. Start with 40-50% of your RDL weight and focus entirely on control.

RDL vs. SLDL for Glute Growth

The RDL is vastly superior for glute growth. The deep hip hinge under load places maximum tension on the glutes as they work to extend the hips. The SLDL shifts tension to the lower back, significantly reducing the glutes' involvement and making it a poor choice for building your backside.

Using Dumbbells vs. a Barbell

Both are excellent tools. Dumbbells allow for a more neutral grip and can help identify and correct strength imbalances between your left and right sides. A barbell is better for progressive overload, as you can load more total weight over time, which is key for long-term muscle growth.

What If I Feel RDLs Only in My Lower Back?

This is the most common mistake and it means you are not hinging correctly. You are bending at your waist instead of pushing your hips back. The fix: cut the weight by 50%. Stand facing away from a wall, about a foot in front of it. Initiate the RDL by trying to touch the wall with your butt. This forces the hip hinge pattern.