How is this different from the Smith Machine Romanian Deadlift?

They are the same hinge on the same machine, done with different knees and depth: here the knees stay nearly straight, the hips stay higher and the bar travels lower, while the Smith Machine Romanian Deadlift keeps a softer knee bend and usually stops around mid-shin. In a barbell study of competitive bodybuilders lifting 80% of their max, the straight-knee version drew more gluteus maximus activity on the way up and the Romanian version more semitendinosus activity. No study has compared the two on a Smith machine, so treat them as close variations rather than different exercises.

Should my knees be completely straight?

No. Keep a slight unlocked bend and hold that same angle for the whole set, so the knees never lock out and never bend further as you lower the bar.

How low should the bar go?

Lower it as far as you can while your back stays flat, which is somewhere around the lower shin for most people. Set the safety stops at that point and stop above them on any rep where your lower back starts to round.

Is the Smith machine version as good as a barbell stiff-leg deadlift?

It trains the same hinge and the same hamstrings, but the rails do the balancing and set the bar path, so it does less for the stabilizers and for learning to keep a free bar close. It is a good choice when you want to focus on the hamstrings, and the Barbell Stiff-Leg Deadlift is the step up when you want the full free-weight lift.

Why do I feel it mostly in my lower back?

Usually because the spine is rounding at the bottom, the hips are not moving back, or you are going deeper than your hamstrings allow. Shorten the range, lighten the load and check that the bar runs over the middle of your feet.

Smith Machine Stiff-Leg Deadlift

What Is the Smith Machine Stiff-Leg Deadlift?

Smith Machine Stiff-Leg Deadlift is a compound exercise that primarily targets the hamstrings and glutes and also engages the lower back, adductors and grip. It is an intermediate-level movement because hinging with nearly straight knees takes good hamstring flexibility and the control to keep the back flat at the bottom, even though the machine takes care of balance.

The exercise is a hip hinge in which the knees stay almost straight from the first rep to the last, so nearly all the work comes from the hips and the hamstrings are loaded at long lengths. The Smith machine's rails fix the bar's path, which removes the job of steering and balancing a free barbell and lets you focus on pushing the hips back and keeping the spine still. It is usually programmed as an accessory after squats or deadlifts, with moderate loads for sets of 8 to 12 controlled reps.

It is a close relative of the Smith Machine Romanian Deadlift, done on the same machine with the same hinge. The difference is the knees and the depth: the Romanian version keeps a softer knee bend and usually stops around mid-shin, while here the knees stay nearly straight, the hips stay higher and the bar travels lower, which asks more of the hamstrings' flexibility. Compared with the free-weight Barbell Stiff-Leg Deadlift, the Smith version cannot rest the bar on the floor, so each rep finishes just above the safety stops, and it takes away the balance and bar-path control the free bar demands. Many Smith bars are also counterbalanced, so the weight you log will not match a free barbell.

The Smith version suits lifters who want direct hamstring work with less balance demand, and trainers who want a consistent bar path for clients still learning to hinge. If you cannot reach below the knees without the lower back rounding, build the pattern first with the Smith Machine Romanian Deadlift or the Cable Pull Through, and strengthen the hips with the Glute Bridge.

Muscles Worked

MuscleActivation

Biceps Femoris: Primary
Gluteus Maximus: Primary
Semimembranosus: Primary
Semitendinosus: Primary
Adductor Magnus: High
Erector Spinae: High
Thoracolumbar Fascia: Medium
Flexor Carpi Ulnaris: Low
Latissimus Dorsi: Low
Upper Trapezius: Low

Instructions

Set the safety stops at about lower-shin height, the lowest point you can reach with a flat back, and set the bar on the hooks at about mid-thigh height.
Stand facing the bar with your feet hip-width apart and toes pointing forward, close enough that the bar sits over the middle of your feet.
Grip the bar overhand with your hands just outside your thighs.
Brace your core, stand tall and rotate the bar to release it from the hooks.
Unlock your knees into a slight bend and keep that same angle for the whole set.
Push your hips back and hinge forward, keeping your back flat and the bar close to your legs as it slides past your knees.
Keep your neck in line with your torso, looking at the floor a little ahead of you.
Lower the bar slowly to about your lower shins or until it nearly touches the stops, stopping earlier if your lower back starts to round.
Drive your hips forward to stand tall, squeezing your glutes at the top without leaning back.
After the last rep, rotate the bar back onto the hooks.

Common Mistakes

Rounding the lower back to go deeper
Reaching for the safety stops past the point your hamstrings allow rounds the spine and moves the load from the hips onto the lower back.
Locking the knees hard
Snapping the knees fully straight or pushing them back into hyperextension strains the back of the knee, so keep them unlocked with a slight, fixed bend.
Bending the knees as you lower
Letting the knees bend more on the way down shortens the hamstring stretch and turns the lift into a Romanian or conventional deadlift.
Standing in the wrong spot under the bar
Because the rails fix the bar's path, standing too far back leaves the bar ahead of the feet at the bottom and pulls the torso forward onto the lower back.
Bouncing off the stops
Dropping the bar onto the safety stops and rebounding takes the control away from the hamstrings at their longest and most vulnerable point.
Leaning back at the top
Pushing the hips through and arching backward at lockout compresses the lower back without working the hamstrings or glutes any harder.

Injuries

Smith Machine Stiff-Leg Deadlift is a medium risk exercise when performed with proper technique. The lower back is the main strain point: with the knees nearly straight and the hips high, the torso works as a long lever, and that demand peaks at the bottom of the rep, especially if the spine rounds to reach a lower position. The hamstrings are at their longest at the same moment, so bouncing out of the bottom or dropping quickly into it can strain them, and grip can give out on heavier sets.

Let your hamstring flexibility set the depth rather than the safety stops, and set the stops at the lowest point you can reach with a flat back. Lower the bar slowly, keep the load moderate, and take time to place your feet so the bar runs over the middle of the foot, because the rails will not let the bar move toward you if you stand too far back.

To make it easier, shorten the range, reduce the load, or switch to the Smith Machine Romanian Deadlift, whose softer knee bend needs less flexibility. The Cable Pull Through and Hyperextension train the same hinge with less spinal load. Once the Smith version feels controlled, the Barbell Stiff-Leg Deadlift adds the balance and bar-path control the rails take away.

Stop the set if you feel sharp pain in the lower back, pain or tingling running down a leg, or a sudden pull in the back of the thigh. Stiffness in the lower back that lasts into the next day is a sign to reduce the load or depth and have your technique checked.

Overview

Primary Focus: Hamstrings and glutes
Equipment: Smith machine
Modality: Strength
Difficulty: Intermediate

Alternative Exercises

Frequently Asked Questions

Q: How is this different from the Smith Machine Romanian Deadlift?: They are the same hinge on the same machine, done with different knees and depth: here the knees stay nearly straight, the hips stay higher and the bar travels lower, while the Smith Machine Romanian Deadlift keeps a softer knee bend and usually stops around mid-shin. In a barbell study of competitive bodybuilders lifting 80% of their max, the straight-knee version drew more gluteus maximus activity on the way up and the Romanian version more semitendinosus activity. No study has compared the two on a Smith machine, so treat them as close variations rather than different exercises.
Q: Should my knees be completely straight?: No. Keep a slight unlocked bend and hold that same angle for the whole set, so the knees never lock out and never bend further as you lower the bar.
Q: How low should the bar go?: Lower it as far as you can while your back stays flat, which is somewhere around the lower shin for most people. Set the safety stops at that point and stop above them on any rep where your lower back starts to round.
Q: Is the Smith machine version as good as a barbell stiff-leg deadlift?: It trains the same hinge and the same hamstrings, but the rails do the balancing and set the bar path, so it does less for the stabilizers and for learning to keep a free bar close. It is a good choice when you want to focus on the hamstrings, and the Barbell Stiff-Leg Deadlift is the step up when you want the full free-weight lift.
Q: Why do I feel it mostly in my lower back?: Usually because the spine is rounding at the bottom, the hips are not moving back, or you are going deeper than your hamstrings allow. Shorten the range, lighten the load and check that the bar runs over the middle of your feet.