There was a post in absoluteunits of a giant basketball player (Hamad Fathy) who is 7’5” and alot of people were commenting about the likely sad state of his knees and back.
My question is if he is fully proportional and athletic with no extra weight damaging his joints, are the forces of gravity enough to do more damage to him just because of his exceptional size?
What else could slowly wear away at someone that large’s body?
In: Biology
> My question is if he is fully proportional ….
See, there’s the issue.
A bone’s strength is proportional to its cross-sectional area, which grows with “size” squared. Similarly, pressures on joints depend on the surface area of those interaction points, which scales with “size” squared.
But weight scales with size cubed, and twisting forces scale with weight times the size, (or proportional to size to the 4)!!
So even if the body is “proportional”, the forces aren’t.
It’s called the square-cube law. Area scales by the square of width/height, but volume scales by the cube of width/height.
Let’s say you take a person and double their heigh while keeping their proportions the same. That person’s muscles and bones will be four times as strong, because by doubling their height you’ll be multiplying the cross-sectional area of their muscles and bones by four.
But the problem is that they’ll be eight times as heavy, because their weight is based on their volume. So you’ve got eight times as much weight on joints, bones, and muscles that are only four times as strong.
This doesn’t just affect people- it’s a basic engineering principle. It’s why you can build a hut with some sticks, but you need steel beams to build a skyscraper. Both mechanical devices and biological bodies face problems when you try to scale them up/down.
If he’s fully proportional, then he’s getting hit by the square-cube law, which means that volume of his body parts increases much faster than surface. It’s bad, because your needs are usually cubed, but your providing capability is only squared. That means that if you were suddenly 2x bigger, you’d weight 8x as much, but your muscle cross-section would only be 4x as big, so now you’re only relatively half as strong as you used to be. Same thing with body heat – you are 8x bigger, but you give off heat through the surface of your skin, which is only 4x bigger, so the disproportion strikes once again.
Because he is not fully propotional. I don’t know the guy, but the mechanics of how your body moves change when you diverge from “normal” height and weight.In the case where you’re taller but not heavier your’re still putting more stress on your joints because the forces involved are still bigger.
If you walk out onto a plank suspended over nothing, the further you get away from the ground its attached to the more likely the plank is to break. Despite your weight not having changed. The stress on the joint is propotional to the distance to the force.
That is to say that if your limbs and frame are longer, your center of mass will also be further away from the joints that move that weight. Therefore increasing the stress they take. That kinda thing can build up over time for very tall people.
Unfortunately, we’re four-legged creatures who decided to hold our spines upright like pool noodles. The more weight, the worse it’s gonna get, regardless of how you try to offset the issue with muscle. (Also I imagine there’s some hard limits to how much muscle a human body can support, due to limitations on food / energy processing)
The problem is that it’s not possible to be fully proportional. The human body just doesn’t scale and that’s the reason why we stabilised around the 2m mark as the maximum height.
To grow taller we need more bone density and more muscle density, but more bone and muscle density makes us heavier which requires more bone and muscle density , which requires more bone and muscle density, which requires more bone and muscle density ….
Latest Answers