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01.01.2011


Why squats with 100 kg are heavier than leg presses with 200 kg

The weight you shift with the leg press is a fraction of what you can shift with a squat. Sports scientists at Arizona State University East published formulas in 2004 that you can use to calculate how many kilograms you can use for squats if you know how many you can use on the leg press and vice versa.





The researchers determined for 30 new strength athletes [Novices] and 30 athletes who'd been training for over 6 months [Advanced] how many kilograms they could just manage to do 10 reps with, of squats and leg presses. The athletes used a proper leg press like the one shown here, where you push the weights away at an angle of 45 degrees. The story below doesn't apply to other types of leg press machines.

As you might expect, the advanced athletes were quite a bit stronger than the beginners.



The first graph below shows how many kilograms the beginners could manage with leg presses and squats. The second graph shows the same, but for the advanced athletes. The graph at the very bottom shows the data for all test subjects.



The researchers used statistics to derive a formula from their data, which represents the relationship between the amount of kilograms at which athletes can do 10 reps of each exercise.

Novices: number of kilograms for squats = kg for the leg press times 0.21 plus 36.

Advanced: number of kilograms for squats = kg for the leg press times 0.31 plus 19.

Everyone: number of kilograms for squats = kg for the leg press times 0.35 plus 2.

If you see someone, and you don't know how long they've been training for, doing 10 reps on the leg press with 200 kg, then you estimate the amount of kilograms they can shift when doing squats by multiplying 200 by 0.35, and then adding another 2 kilograms to the result. So that's how you know why squatting with 100 kg weights is heavier than doing leg presses with 200 kg.

Source:
J Strength Cond Res. 2004 Aug; 18(3): 567-71.

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