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Comment by Noumenon72 | Hacker News Reader

> Elite sprinters can apply peak forces of 800-1000 pounds (3560-4450 Newtons) to each limb. Beyond ~1300 pounds, ideal human leg bones would surely break[1].

I followed the link and it just said

> If you're looking for the specifics to snap a piece of your skeleton, it takes about 4,000 newtons of force to break the typical human femur.

So the sprinters are already producing that much force (900 pounds) and the 1300 notion seems unsupported. Not to mention that applying the force with different amounts of torque might not break the bone, since bones are 10x stronger in compression so can withstand a lot more force longitudinally.

1: https://www.discovery.com/science/force-to-break-bone

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I can't access the discovery link from europe.

From your quotes, there seems to be an important difference: in the first quote they talk about "ideal human leg bones" and in the second one about a "typical human femur".

I'm certain that an elite sprinter blessed in genetics has leg bones significantly stronger than the average human. Bones also get stronger from repetitive exercise.

I would guess there also may be a difference between the two cases in that the force needed to break a leg wasn’t measured by compressing it, but by exerting force perpendicular to its length.

Even if it isn’t, there are so many ways to measure breaking strength that it’s unlikely the two cases are perfectly comparable.

This was my assumption. The original article implies parallel force, which I imagine has far higher limit than perpendicular. Eg trying to chop a 1x4 in half long ways probably takes quite a bit of force(and a touch of stupidity).

Your bones get stronger when regularly stressed. Bone is added on the inside, not the outside, so you won't notice it.

I recall reading once that a pitcher's right arm had quite a bit more bone in it than his left.

For a bit of scale on what we know the human leg can handle without breaking: the best drug tested, sleeves-only squat in the world is 490 kg (Ray Williams IPF Worlds 2019). Drop the drug testing and add multi-ply squat suits and the record is 590 kg (Nathan Baptist, UPA Utah Kick Off Meet 2021). Granted: these are two-footed squats and you run with one leg at a time.

Alternatively, look at Olympic weightlifting. While the weights used in the clean and jerk and snatch are less that used in the squat in powerlifting, the instantaneous forces are much greater. I don't think 1300 lbs is anywhere near enough to break a human femur if we're talking compressive forces, lateral force is a different story.

Olympic-style lifts are among the most powerful things a human can do. Elite athletes can push beyond 5kW at the peak of exertion. This is why technique is so important. The forces involved are insane once you go beyond 200lbs or so. The snatch can be extremely troublesome if you do it wrong. Clean and jerk is more tolerant to bad form.

oooh yeah the speed is definitely something to consider for them. Hmm. Kinda wanna grab some hookgrip slow-mo edits and do JV science with them. Kinda don't because I have shareholder value to create.

And could you add Baptist's weight to that? He is probably more than 150kg.

hahah dog he weighed 226.5kg. https://www.openpowerlifting.org/m/upa/2104#nathanbaptist

Ray Williams weighed 190.4kg for his https://www.openpowerlifting.org/m/usapl/2019-03-02

Also so sorry, I got the meet wrong but the year right. It was the 2019 USAPL Arnold SBD Pro American

So his legs (or at least his ankles) are supporting more than 800kg between them

I somehow did not think of that. Very true!

Not to down play the "what's possible", but it's important to note that bone strength depends on stimulus and nutrition just as much as muscular and connective tissue strength. Those athletes bones are likely far stronger than the average human of the same size without training.

Oh yeah, in fact Gene Rychlak (first lifter to bench over 1000lb) said he could feel his bones bending during the lift. Training is getting your body adapted to the movement, and that for sure includes bone density. I'm guessing our 100m runners are also pretty dense.

Tendons may be the limiting factor here. They are soft tissue that has an elastic limit that is likely to be lower than solid non-deformable bone. Exceed that and tendons will either tear or pathologically lengthen.

Worth noting that the femur is the strongest bone in the human leg...

I think we should be considering the weakest link in the chain here, the femur arguably being the strongest.

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