MedX vs Free Weights for Back Pain
Short answer: they are different tools for different jobs. Free-weight compound lifts - the deadlift, the back squat, the Romanian deadlift - load the whole posterior chain in a coordinated hip-dominant pattern. The MedX lumbar extension does the opposite, isolating the lumbar extensors with the pelvis mechanically locked. For a well-coached lifter with a sound back, free weights are an excellent choice. For someone whose lumbar extensors have learned to hand the work to the hips, the MedX exists for a reason. The protocol behind our floor is High Intensity Training (HIT) - a slow, controlled, one-to-one strength protocol, distinct from HIIT (High Intensity Interval Training).
What the MedX lumbar extension actually does
The MedX lumbar extension is built around one engineering idea: lock the pelvis, and the spine has to be extended from the lumbar extensors themselves. The restraint clamps the pelvis and femurs, so the gluteus maximus and the hamstrings cannot rotate the pelvis backward and do the job on behalf of the lower back. The lumbar erector spinae has to lift the load.
The lineage runs through Arthur Jones, the engineer who founded Nautilus in the early 1970s. His observation was that strong lifters often had weak, sore lower backs, and his guess was that the hip extensors were doing work the lumbar extensors should have been doing. The machine was his attempt to remove the hips from the equation.
From the late 1980s onward, an independent programme at the University of Florida, led by Michael Pollock and James Graves, put the machine through more than thirty peer-reviewed studies - still the largest body of equipment-specific research on any single piece of strength equipment for the lower back.
What deadlifts and squats actually load
Free-weight compound lifts load the lumbar spine, often heavily. That is not the same as isolating the lumbar extensors.
In a deadlift, the bar moves because the hips extend. The gluteus maximus and the hamstrings are the prime movers. EMG reviews of the deadlift show high activity in the erector spinae too, but its job there is largely isometric: keeping the spine neutral while the hips do the work. The pelvis is free to rotate, which is what makes the lift powerful, and what masks how much the lumbar extensors are actually contributing.
The squat is similar. Heavy compressive load on the lumbar spine, yes. A neutral-spine bracing demand on the erectors, yes. A direct, isolated stimulus to the lumbar extensors as prime movers, no.
Free weights load the spine. The MedX loads the lumbar extensors. Both can be useful. They are not interchangeable.
“Free weights load the spine. The MedX loads the lumbar extensors. Those are not the same thing, and the difference is the whole point of having both kinds of tool in the world.”
Yoram Sher · Director and head coach
The fair case for free weights
Free weights have a great deal going for them, and we are not in the business of telling well-trained lifters their deadlift is wrong.
They train coordination, balance and bracing as a whole. They teach the hip hinge, which transfers to almost every loaded task in daily life - lifting a child, moving furniture, picking up a bag of compost. They build the entire posterior chain in one movement, with decades of evidence behind them.
In the back-pain literature too, the evidence is good. A 16-week deadlift-based programme has been shown to reduce subjective pain by around 70%, lower disability scores, and improve lumbar extension endurance. Stuart McGill, the spine biomechanics researcher most cited on this in lifting circles, is clear that free-weight loading can be done well for many people with back histories - provided the lifter can hold a neutral spine under load and trains with good coaching within a sensible margin.
Where the MedX wins
The same research that supports deadlift rehab also tells you who it is best for. The Berglund group found that the clients who benefitted most from deadlift-based rehabilitation were those with less pain, less disability, and higher baseline back endurance. The ones who did less well were those with high pain, high disability and poor lumbar endurance - the group whose lumbar extensors had stopped pulling their weight.
That is the group the MedX was built for. A separate Florida finding is informative: twelve weeks of training on conventional, non-pelvic-restrained "low back" machines produced no measurable strength gain in the lumbar extensors themselves, despite gains in the hips and hamstrings. Without restraint, the trainee simply learned to do hip extension better.
Reviews of isolated lumbar extension training - the 2015 Steele review in PM&R, and a 2025 meta-analysis in Scientific Reports - find that the work, performed once a week to a high level of effort, produces meaningful improvements in pain and disability for chronic low back pain. That once-a-week dose is also the dose on the super-slow HIT protocol we run.
The fair case against the MedX
The MedX has real limits, and pretending otherwise would be a sales pitch rather than a comparison.
The machine is expensive, takes significant floor space, and is found mostly in dedicated strength-rehabilitation facilities. In Europe that means Kieser clinics and a handful of independent studios. In the UK, you can count the MedX-equipped floors on your fingers. Free weights are everywhere, cheap, and scale to any setting. Access is a genuine problem for the MedX in a way it is not for a barbell.
The MedX also loads one joint axis in one plane. It does not teach a hip hinge. It will not improve your deadlift form, and it will not carry over directly to picking up an awkward load from the floor. For someone whose goal is barbell sport, it is at best a useful complement. For someone whose goal is a back that can get through the next decade without flaring, it is built for that.
How to choose, honestly
A simple decision aid. An introduction session will tell you more than an article can.
- Free weights, well coached, sound back. If you train under a competent coach, can hold a neutral spine under load, have no back history limiting you, and want sport carryover - the deadlift, the squat and their variants are an excellent choice.
- MedX, supervised, with a back history. If you have long-standing lower back pain, a plateau on physiotherapy, deconditioned lumbar extensors, or a back that has stopped tolerating the loads you used to put through it - the MedX is the tool built for that case.
- Both, in sequence or in parallel. Many of our clients do free-weight work elsewhere and use the MedX here once a week as the piece their other training does not give them.
What this looks like at Ultimate Strength
One 45-minute session a week, by appointment, in a private studio in East Finchley, North London (N2). A Kieser-trained coach stands next to you throughout. The centrepiece for back work is the MedX Core Lumbar Strength machine - the same generation used in Kieser clinics across Europe - alongside the MedX lumbar extension and the rest of our floor .
We are not a clinic. We do not diagnose, prescribe, or replace any care your doctor or physiotherapist is providing. What we do is the loaded strength training part, slowly, in writing, week by week. The dedicated service page is Lower Back Rehabilitation . The sibling article Is strength training safe with back pain? covers when loaded strength work is appropriate at all.