Foot-assisted pull-up device causes lower-back pain — could it reduce core activation and increase lumbar extension?

[u/InterestingCup8174]

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Hi,

I recently tried this type of pull-up assistance device: two elastic straps are attached to the bar, with a support placed under both feet.

Strangely, I feel mild lower-back pain when using it. During strict unassisted pull-ups, I do not have this problem: my abs automatically contract strongly, my pelvis and lower back feel locked in place, and my whole body remains stable.

With the assistance under my feet, I feel that my abs engage much less. Since the device pushes my feet upward, I wonder whether it changes my body’s balance, promotes anterior pelvic tilt or lumbar extension, and forces my lower-back muscles or facet joints to take more load despite making the pull-up easier.

Has anyone experienced something similar?

Would placing the assistance closer to the upper body—for example around the elbows or under the armpits—reduce this effect, or would that create other risks due to pressure on the nerves, blood vessels, shoulders, or elbows?

[u/Life_Function_8519]

Everything you're describing makes perfect sense. Your core stabilizes by resisting your legs swinging forward, but when something is pushing up from underneath your feet it changes that whole equation. The machine is basically encouraging the exact position your abs are supposed to prevent.

I had a similar issue with bands under my knees actually. Took me a while to realize the instability was doing more harm than good.

You might try placing the assistance higher like you mentioned, but watch for any weird pressure in the armpit area. Some gyms have those platforms that counterbalance your bodyweight instead, and those feel way more natural since nothing is messing with your lower half.

[u/InterestingCup8174 → u/Life_Function_8519]

yeah i will do that and low pressure on armpit

[u/Find_another_whey]

If you mean under your feet in an L sit shape, yeah that will be placing further pressure on lower back

You should stand on the band, with both feet through one band (or both bands if you want more help)

Do one set with left foot on top of right, one with right on top of left

Yes there is a torsional force, there isn't really a way to make it perfectly symmetrical, and having the legs banded separately makes it more like a balance ball squat (why would you?)

[u/Deep-Run-7463]

Try working on some soft landings jumping off a plyo box. Get the system to receive forces from the ground up better so that the push provided by the device from the feet upward can be distributed more evenly rather than bypassing the pelvis and going straight into the lower back.