I have some questions concerning the strength system.
Here an example:
Spider-Man is class 15. Does that mean he can lift 15 t with
A) One Arm or B) Both Arms
When he can lift it with both arms (what I think is the right thing)
then he can lift 7,5 t with one arm right?
And there is another question.
The leg muscles are stronger than the arms,
so Spidey should be able to lift more with his legs right?
So his kicks should be more powerful than his fists.
Yep, as for the legs, i wouldn't be so sure. It could work for Spiderman the way you say, because he's got the proportionate abilities/powers of a spider or whatever, but not al people can lift more with their legs than with their arms.
Typically, the average person can leg-press perhaps 3 to 5 times what s/he can military/overhead press. Next time you're in a gym, see for yourself.
Discrepancies result when, for example, a guy works out on his upper body but not his legs. Then a military press can be closer to a leg-press -- or even exceed a squat.
IMO, squats are not the best way to measure "pure" leg strength because the mechanical advantage (leverage) is much poorer than with a leg press.
As an example: in the 1956 Olympics, Paul Anderson -- at the time considered the strongest man ever, and still rated up there (and he did Not use steroids!) -- became the first person to military press 400 pounds (without any backbending). His squat record still holds at about 1200 pounds.
His most powerful lift was the back lift (very similar in leverage to a leg-press). Here he lifted over 6000 pounds.
I believe Sri Chimnoy "recently" bested this with a "straightening up" lift of about 7000 pounds. Basically, he stood under a weight with one arm straightened out under the platform and then straightened his legs a few inches.
In any event: given the leverage, legs are several times stronger than the arms/shoulders.
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That is indeed what i meant. Most people i know that work out usually work their upper body a lot, and their legs almost not at all. Most heroes that are shown to have superstrength are depicted as having huge upper torsos, but not such imposing legs (Exception: juggs, hulk, supes and maybe a few more).
Emphasizing your point, how the hell does Mr Incredible do his mighty feats without, at the very least, snapping his ankles?
Also the superhero toons (eg, JLU) tend to depict the mighty ones with immense upper bods and next-to-nothing thighs.
Anyone remember a Huge-upper-bodied wrestler with eeny-teeny legs from the ol' Warner Bros/Bugs Bunny toons?
Related question: what's up with the Big Feet in so many anime-like toons, or even in the "anime-esque" drawing styles of some of the DC artists (eg, Teen Titans in OWAW)?
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Shinier than a speeding bullet.