How does a 125# stack have 300# resistance?
I've asked this question again and again, but I've still never gotten an answer to my question.

I understand the "band" type because as the band stretches, there's more tension. I have one.

I'm asking about the "cable stack" type of home gym. I just got one with a 125# stack. It claims to have up to 300# resistance. How? When I have the pin set at 100# on the stack, there is no more than 100# equivalent of free weights (if that). It's the case on every exercise (bench press, butterfly, etc.). How do get 300# resistance...or 200...or 150?

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    Can you share a link to the one you got? – C. Lange Jan 24 at 6:46
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    I've found out that the same exact gym issold through different sources. I thought I was getting mine through the maker. – 71don Jan 25 at 18:51

Your machine uses mechanical advantage (or disadvantage) to multiply the resistance of the stack.

The machine presumably has a pulley system. Pulleys can multiply or divide the load that they are acting on, trading off against pulling distance. So for example, you can set up a pulley system to lift a 200lb weight with only 100lb of force acting on the other end of the pulley system, but in order to raise that 200lb weight by one foot, you would need to pull through two feet of cable. This would be called a 2:1 mechanical advantage.

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The pulley system in your home gym works the opposite way to this. It is configured to made it harder to move the stack, such that perhaps for every three pounds of force you apply to the cables, only one pound force is applied to the weight stack. The trade-off then is that the weights must move three times as far as the cable is pulled, so you need a very tall rail for the weights to move up and down.

I can't be sure of the exact specifications of your gym, but 125:300 is not exactly 1:3. I would speculate that it is a 1:3 pulley system and there is actually only 100lb of moving weight (and the additional 25lb are non-moving parts).

  • I somewhat understand that principal in pully systems. That’s why when this one advertised as a 125# stack with 330# resistance, I thought I could get 200+ #, which is why I bought it. However, that’s not the case. As said above, when I have the pin set at 125# on the stack (the max) , there is no more than 125# equivalent of free weights. I wish the manufacturers would explain they get it.. – 71don Feb 1 at 23:26
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    @71don -- it's purposely misleading for advertising. You've got 125 lb on the stack and at least one movement that you can perform on the home gym has a resistance equal to 330 lb. – C. Lange Feb 2 at 2:05
  • I do not see where there are any "movements" that are more than 125#......unless I sit on the gym and try to lift it up :). If there are, I'd use it. – 71don Feb 9 at 22:49

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