Deadlifts hurt your lower back most often because your lumbar spine is flexing under load instead of staying in a neutral position. This shifts mechanical stress from your hip and leg muscles onto the smaller structures of your lower back. About one in four powerlifters experiences lower back pain, and over a third of all powerlifting injuries involve the lower back, making it the single most common site of pain in the sport.
The good news: the pain usually points to a fixable technique or mobility issue, not a structural problem. Understanding what’s happening in your spine during a deadlift makes it much easier to identify and correct the cause.
What Happens to Your Spine During a Deadlift
Your lower back absorbs enormous forces during a deadlift. At the L5 vertebra (the lowest segment of your lumbar spine), compressive forces can reach roughly 8,000 newtons in generally fit male lifters working at 75% of their max. During a true one-rep max, those forces can climb as high as 18,000 newtons in men and 8,000 in women. To put that in perspective, 18,000 newtons is roughly the weight of a small car pressing straight down on a single spinal segment.
On top of compression, your spine also handles shear forces, which push one vertebra forward relative to the one below it. These range from about 1,300 to 3,300 newtons depending on the load, your sex, and your experience level. Shear forces concentrate at the L5 level and are the type of loading most associated with disc injuries and ligament strain. They increase sharply when your lower back rounds, because a flexed spine redirects force from a compressive direction (which your spine handles well) into a shearing direction (which it handles poorly).
The torque on your lumbar spine also scales directly with load. At 10% of your one-rep max with a straight bar, the net moment at the lower back is around 245 newton-meters. At 80% of your max, it nearly doubles to about 447 newton-meters. Every jump in weight amplifies the demand on the muscles and connective tissues that stabilize your spine.
The Most Common Technique Causes
Rounding Your Lower Back
When your lower back rounds during the pull, the load shifts from the large muscles of your hips and thighs onto the passive structures of your spine: discs, ligaments, and the small muscles between vertebrae. These structures aren’t designed to be primary movers under heavy load. A rounded spine also increases the moment arm between the barbell and your lumbar joints, which means the same weight creates more torque on your back. This is the single most common reason deadlifts cause pain.
Letting the Bar Drift Forward
The bar should stay close to your shins and thighs throughout the lift. When it drifts even a few inches forward, the effective lever arm between the weight and your spine gets longer. Your lower back muscles then have to work harder to keep you from folding over. Keeping the bar near your center of gravity is one of the simplest ways to reduce lumbar strain.
Starting With Your Hips Too High or Too Low
If your hips start too high, the deadlift turns into a stiff-legged pull that loads your back from the very first inch. If they start too low, you’ll likely lose tension and let your back round as the bar breaks the floor. The right hip height depends on your proportions, but a good cue is to position your shoulders directly over or just in front of the bar, with your shins touching it.
Fatigue-Related Breakdown
Form doesn’t just break down when you go too heavy. It also breaks down when you do too many reps. Research on repetitive deadlifting shows that fatigue increases trunk flexion over the course of a set, which in turn raises both compressive and shearing spinal loads. Your last few reps of a tough set are where injury risk climbs, because your stabilizing muscles tire out before your prime movers do. If your back always feels fine on the first few reps but aches after high-rep sets, fatigue is likely the culprit.
Hip Mobility Problems That Force Your Back to Compensate
A deadlift is fundamentally a hip hinge: you bend at the hips, not at the spine. But if your hips don’t have enough range of motion, your lower back picks up the slack. Limited hip mobility, particularly in internal rotation and the ability to flex deeply at the hip socket, forces your pelvis to tuck under at the bottom of the lift. This “butt wink” pulls your lumbar spine out of its neutral curve and into flexion right at the point where loads are highest.
Tight hamstrings create a similar problem. When your hamstrings can’t lengthen enough to let your pelvis tilt forward, your lower back rounds to reach the bar. Many lifters who feel pain only at the very bottom of the pull are dealing with a mobility limitation rather than a strength problem. Improving hip range of motion lets the hip muscles do more of the work, which typically reduces back stiffness and pain. A simple test: if you can’t sit in a deep squat with your heels flat and your lower back relatively straight, hip mobility is likely limiting your deadlift setup.
How Bar Type and Stance Affect Your Back
Conventional deadlifts place your trunk in a more horizontal position, with trunk angles ranging from about 67 to 73 degrees from vertical. Sumo deadlifts keep the trunk more upright, between roughly 57 and 65 degrees. A more upright trunk reduces the moment arm on your lumbar spine, which is one reason people with back sensitivity often find sumo style more comfortable.
Hex bars (also called trap bars) also reduce lumbar loading compared to a straight bar. At 80% of max, the net moment on the lower back with a hex bar is about 409 newton-meters versus 447 with a straight bar. That difference is roughly 10%, which may not sound dramatic, but it adds up over hundreds of reps per month. If back pain is your main concern, a high-handle hex bar is the gentlest option because it shortens your range of motion and keeps the load closer to your center of mass.
Do Weightlifting Belts Protect Your Back?
The short answer is that the evidence doesn’t clearly support belts as injury prevention tools. A major review by the National Institute for Occupational Safety and Health found no conclusive evidence that belts reduce spinal compression, increase spinal stiffness, or remind lifters to maintain proper form. The claims that belts increase intra-abdominal pressure in a way that meaningfully reduces spinal force remain unproven.
More concerning, some research suggests that people who wear belts believe they can lift more weight, which may create a false sense of security. If you use a belt as a substitute for core stability and good technique, you may be exposing yourself to greater risk, not less. Belts can be a useful tool for experienced lifters who already have solid form, but they aren’t a fix for the underlying causes of deadlift-related back pain.
Building a Pain-Free Deadlift
The most effective approach combines core stability training with hip mobility work. Spine biomechanics researcher Stuart McGill developed three exercises specifically to build the endurance and stiffness your core needs to protect your lower back under load.
- Modified curl-up: Lie on your back with one knee bent. Place your hands under your lower back to maintain a slight arch. Lift only your head a few inches off the ground, keeping your chin tucked, and hold for 10 seconds. Your lower back should not move at all during the hold.
- Side plank: Lie on your side with knees bent, propped on your elbow. Lift your hips so only your knee and forearm support you. Hold for 10 seconds. This trains the lateral muscles of your trunk, which are critical for spinal stability but often neglected.
- Bird dog: From hands and knees, extend one leg back and the opposite arm forward without letting your lower back shift or rotate. Hold for 10 seconds. This teaches your spine to stay neutral while your limbs move, which is exactly what happens during a deadlift.
For all three, use a descending pyramid: start with something like 6 reps, then 4, then 2, holding each for 10 seconds. These aren’t meant to be exhausting. The goal is endurance and motor control, not fatigue.
For hip mobility, a figure-four stretch (sitting with one ankle crossed over the opposite knee, then leaning your torso forward) targets the external rotation your hips need at the bottom of a deadlift. Spending two to three minutes per side before training can make a noticeable difference in how your setup feels.
Soreness vs. Pain: What to Pay Attention To
Mild muscle soreness in your lower back after deadlifts isn’t necessarily a problem. Your spinal erectors are working muscles, and they get sore like anything else. The key distinction is location and timing. Muscular soreness feels diffuse, sits in the meaty part of your back on both sides, and fades within 48 to 72 hours.
Pain that’s sharp, located on one side, concentrated right at the spine, or that shoots into your glute or leg is a different signal. The same goes for pain that shows up during the lift itself rather than the next day, or stiffness that lasts more than a few days. These patterns suggest the load is going through structures that shouldn’t be bearing it, and continuing to train through them typically makes things worse, not better.