“During the online Resistance Exercise Conference, there was a short segment where a trainer (Skyler Tanner) did a demo showing how you could use a Medex leg extension machine to do hip thrusts. He suggested that the fall off cam on the leg extension addressed the issue that Bill DeSimone had with the hip thrust exercise, namely that when done with a barbell, the resistance curve is all wrong.”
Just to clarify, since my name was attached to this: I do not encourage using the Medx LX this way. Single exercise stations are designed to be stable when used only that way. Use a Vertical Chest Press seat for step ups, or a curl station for pec stretches, and if it tips or the user gets injured, that is ALL on you.
The torque mismatch is only one of my issues with the Barbell Hip Thrust. Forcing hyperextension at the top, forcing loaded lumbar flexion at the end of the set at the bottom, and putting the load directly over the hip joint (creating zero moment arm for the hip extensors).
A low tech alternative: The Joint-Friendly Fitness Project by Bill DeSimone » Barbell Hip Thrust v. Reverse Lunge: the Biomechanics — Kickstarter
If Nautilus continued their station, both legs at one time, approximately 90 degrees of movement, from 90 degrees flexion at the hip to 0 degrees (full hip extension), with the cam widest (or resistance leverage greatist if plate loading) at 70 degrees flexion, probably requiring a seat belt… this combination would load the joint angle for peak muscle torque without risking forced hyperextension, twisting of the spine, or forcing the lumbar spine in flexion, i.e. all the benefits with none of the risks.
I believe Doug Brignole makes a similar recommendation, use a reverse lunge if a proper hip extension machine isn’t available. (His preference was one of those multi-hip machines where you move a rotary resistance arm while standing on the other leg).
My recollection is that with the duo hip and back, you could hyperextend (overstress) the low back by driving both legs down too far at the same time. If you leave one leg up while the other drives down (unilateral extension), that seems to protect the lumbar spine.
It does appear to me that in both exercises (hip thrust and reverse lunge), the weight is applied at the hip joint, But the manner in which the load transfers through the spine is different: vertical spine and axial spinal load (for any external weight that might be held in the hands) for the reverse lunge vs horizontal spine and shear stress on the spine for the hip thrust. The former is likely safer. (And people typically use a lot more weight for the hip thrust.)
Couple of issues with the duo. Holding one glute at extension means holding at a weak angle. Twisting the lower back more likely than if both sides drive. And the extreme range we were encouraged to use meant that side loaded in flexion.
As far as the argument that walking and running use alternate legs so should the hip extension: jumping and sit-to-stand use both at the same time.
At Sports Training Institute in 1983, we had all versions at the time, the duo and two different both side models. The issue with the both sides models was having to crank the bed so the users hips lined up with the axis of the cam. As the knees started to approach their armpits and the spine rolled up, people tended to freak. Between that and the coordination for the duo and short attention spans, all three gathered dust.
I’m guessing that you now feel that the emphasis on full range of motion was overdone?
Thinking about this a little more, I wonder if a lot of issues aren’t introduced by using a belt for restraint? Strapping a belt across the front of the pelvis does create a moment arm relative to the axis of the hips, and you are doing this with a pretty powerful muscle group. Then from the pelvis to the shoulders, you have another lever arm. Probably pretty tempting to tilt the pelvis, brace against the belt, in order to be able to drive the hip extension more powerfully???
Of course. But I was thinking a bit more broadly, comparing the traditional hip and back machine against exercises that are less explicitly isolation exercises, but still somewhat effective for the hip and glutes. You don’t need a restraint belt to do a reverse lunge. And the standing multi-hip machine doesn’t require a restraint belt. Maybe they don’t isolate the target muscle group as well, over as large of a range of motion. But then you also don’t have to worry about how to keep your butt on the bench, or rely on restraints to produce the kind of motion you want.
That is just a specific example of something I’ve wondered about more broadly: If you start with the human body as a stick figure, with simple joints at the ankles, knees, and hips, and attached to a lever labeled “spine”, then building a machine to isolate a movement around the hip joint might seem straightforward. But the structure you are dealing with in reality isn’t a stick figure and there are a lot of important details that get lost with that simple model. Perhaps the absence of those details can produce unexpected problems. Maybe some of these isolation machines end up being not as good as hoped, because of that sort of generic problem, overly simplistic modeling of the movement?
That is more like it!
Great answer!
I doubt the perfect machine exists!
The best position for exercise is generally a standing position. Since before birth, the human body/mind is hard-wired to cope with gravity. Regardless of what ARX states, gravity is important as regards exercise. Ditto speed of movement, as a computer/electric motor governing the speed of body movement patterns is most likely a neurological inhibitlor.
Likewise a glute machine would need to incorporate the leg including the feet. It most likely need to deal with multiple strength curves of the involved muscles.
The Nautilus Duo-Squat was good start, but could cause back stability problems, not to mention shoulder compression issues.
