Why You Shouldn’t Trust the Numbers on the Scales
Why can you do 250 pounds of leg press at a regular gym, but only 200 pounds if you go somewhere else in town? You haven’t suddenly become weaker, and contrary to popular myth, it’s not because one gym is lying to you to flatter you. The machines are just different .
Machine design matters
Take the leg press for example, as almost every gym has it. It’s a car where you have some kind of seat and some kind of platform for your feet. You push with your feet to move the platform while the seat is in place, or vice versa.
There are many different ways to build this type of car. Some are upright, with their legs just above the hips. Some of them are located horizontally. For some, the seat slides down the ramp, dragging a stack of loads with it. Each one is a completely different machine, and it should come as no surprise that the one with the tilt and weight stack is calibrated differently than the one where your feet are above you and you load weight plates onto it.
Let’s go back to elementary school physics for a moment. When a machine has a lever, such as a shoulder press machine, arm length changes the amount of mechanical advantage (or disadvantage) you have in lifting the weight. The number of pulleys and cables in a wire saw can also change the force required to move a weight stack. If the weights are moving on an incline, the steepness of the angle affects how easily they will move.
And even when you are comparing two cars that appear to be identical, there may be slight differences. One may be better lubricated than the other, allowing parts to slide more easily. They may not be exactly the same either; the manufacturer may have moved the pulley to a different location between the 2018 and 2019 models. You get the idea.
By the way, cars are not equivalent to free weights. The fact that you can leg press X pounds does not mean that you can load the barbell on your back and squat with the same weight.
So are numbers really meaningless?
Not at all. The numbers matter on this machine . If one of the cymbals in the stack reads 50 and the next cymbal reads 55, then you know that if you can do 55, you are stronger than when you could only do 50 reps.
When you visit a new gym, be careful. If you could do eight reps on pin 55 in your old gym, find a weight you can do eight reps on on your new machine. It doesn’t matter what the number is on that weight, or how much the weight stack weighs, if you could get it out of the car and put it on the scale.
Think of it like in-game currency: you wouldn’t waste time searching on Google for how many Monopoly dollars equals Roboxes , because they have no reason to ever match each other in any meaningful way. Everyone is useful in their own world and nowhere else.
So yes, be sure to write these numbers down in your training diary . They will help you track your progress. But don’t expect them to be the same on another car in town.