Weightlifting Machines with Side-Mounted Weight Stacks

Just wondering if weightlifting machines with rear mounted weight stacks, like a leg extension or pullover machine would be better distributing out the resistance on both limbs of the body evenly as opposed to side mounted weight stacks…example: a leg extension machine with a weight stack mounted on the right side of the machine…would the right and left thigh handle an even amount of resistance or would the right thigh bear most of the resistance? Thoughts or opinions?

Depends on the design TBH.

On a side loaded machine - if the centre datum of the link bar is directly in line with the centre of the stack and the material properties of the link system are strong enough - it won’t make any difference. If the link bar is offset there may be some slight (marginal) bending bias towards the stack side, especially if the materials used in the link system are not strong enough. If the bending moment occurs there will be more friction on the guide rods from the offset and the weight stack will drag.

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I have a feeling most people reading Jeff’s answer won’t actually understand it.

The basic answer, for practical purposes, is that it doesn’t matter, UNLESS the two sides actually move independently of each other. On a ‘regular’ leg press, it will never matter, as long as you don’t tip the machine over by overloading one side, lol. I’ve loaded hundreds of pound just on one side of various machines, with no issue.


What? I am just a lowly mechanical engineer, and I understood it. I kid.

I have in times tried to explain physics to lifters. It is frustrating, but I have to remember that I probably didn’t understand these things at one point.

A guy was practicing a frame deadlift for a comp with a hex bar. He had it on blocks with the handles down. I told him it would replicate the frame better on shorter blocks (same height) with the handles up. He thought I was crazy since both were neutral grip from the same height. I tried to explain the weighs center of gravity being in line with the handles down position, which allows the handles to tilt back and forth. I don’t think that made sense to him.

Then I asked which was easier: farmers carries with farmers handles or dumbells. Now the dumbell has an additional degree of freedom in it’s movement (it can rotate and tilt), but that clicked.

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