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Leg Efficiency

by Outblaze
Tags: efficiency
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Apr5-05, 06:26 PM
P: 12
I know it's 35% but can someone provide a link?
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Apr5-05, 07:18 PM
P: 61
I am not really sure about numbers but I heard the knee is backwards. Or it should have been backwards. Of course the knee itself is a mess too. The light sensitive cells in the eyes are also backwards. I heard the jaw and the arms are terrible design too. I am sure there are also very inefficient things on the biochemical level. The spine is also a poor design for a creature that lives on land. I heard all mammals have back pain/problems.

I am not sure if this is what you meant, but personally I would be very interested in a web page with an alternative human design.
Apr5-05, 09:30 PM
P: 51
What do you mean by "backwards"? Especially referring to the light sensors in our eyes?
I read that humans have back pain because it was pretty recent in evolutionary terms that we became bipedal, and our backs were really designed for a monkey-like lifestyle and haven't had time to fully adapt yet.

Apr6-05, 01:32 AM
P: 540
Leg Efficiency

About the light sensitive cells in our eyes:
The light receptive cells in the retina (the rods and cones) are oriented in such a way that the part with the pigments that "captures" the light is on the outer site (i.e. towards the edge of the eye and not towards the pupil where the light is coming from). Moreover there are other cells, which are involved in signal transduction, on top of the light receptive cells so that the light has to travel through all these cells to reach the pigments that will repond to the light in order to start the whole process that makes you see it.

I wonder about the knee though, I mean in what way is it backwards?
Apr6-05, 10:10 AM
P: 61
I think the eye thing is clear now.

About the knee, now let me first say I am not sure about this, I am not an engineer or something. But I was told or I read that it would be more efficient to have the knee cap stuff inside the knee hole, so at the backside.

I also found this SF picture of some creature. And it even has the joint bent the other way. I am not sure if this is smart.

I did find this:

Seems that that person suggests that a knee without a knee cap that would bend the other way would be better.
Apr6-05, 11:57 AM
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DocToxyn's Avatar
P: 432
I'm sure there are numerous examples of mechanically better designs that only work under specific circumstances and therefore have not been adopted by all species. Insects are much stronger than mammals, on a body weight basis, due to the leverage afforded by having their skeleton on the outside, but the trade-off might be that insects can only get so large before their less efficient respiratory system can't keep up.

It really comes down to the whole being greater than the sum of its parts. It's true that humans and other animals have, what physicists or chemists might call, innefficient systems, but we also have some pretty good designs. The deterity of our hands, structure of the larynx to allow speach, a rather complex brain are a few examples. Over all when you balance the good designs with the bad, I'd say we come out on the positive, at least that's what our population growth indicates.
Apr6-05, 12:00 PM
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P: 2,021
Scientific American had a special issue a year or so ago where they speculated on such improvements to the human body. But I don't have a copy. Anyone else?
Apr6-05, 06:42 PM
hypatia's Avatar
P: 1,298
perhaps you mean this
Apr6-05, 08:20 PM
P: 540
here is the article that Phobos probably meant:

Indeed backwards bending knees are proposed
Apr6-05, 10:00 PM
P: 552
Now that's interesting because I have both played Starcraft (where that protoss alien image comes from) and read that Scientific American article. Totally random experiences combining in a single thread.
Apr8-05, 05:17 PM
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that was the one, gerben - thanks
Apr13-05, 02:22 AM
P: 540
Quote Quote by DocToxyn
.....It really comes down to the whole being greater than the sum of its parts. It's true that humans and other animals have, what physicists or chemists might call, inefficient systems, but we also have some pretty good designs.... Over all when you balance the good designs with the bad, I'd say we come out on the positive....
Yes, I think you are right. After having read the Scientific American article I am not very convinced. The improvements that the authors propose are just more of the same, like bigger bones, more muscles, thicker disks between vertebrae in the spinal cord, more ribs, more valves in the veins and some other "improvements" that would also lead to new problems that would have to be overcome. They do not offer any improvement that will not also have some counter effect.

It certainly did not offer convincing options that would ‘obviously be better’ than what we have now. I also still do not see why a backwards-bending knee would be better. Especially, if you consider what this would require of the necessary musculature.

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