Prosthetic Leg explanations and advice.

[Thundagere]

Yeah, I ask way too many questions.
Anyhow, I was reading on prosthetic legs and I noticed that one runner said he had to run on the balls of his feet with the prosthesis on. Having done this and suffered tendinitis due to too much tension when running, I thought about trying to make a prosthetic leg that tries to act as more of a shock absorber, to sort of relieve the pressure and make it easier to run and lower chances of injury.
This is what i was thinking of
http://img40.imageshack.us/img40/2817/p7190652.jpg

Possibly minus the bottom low spring constant springs. I was thinking of making it for the experience, try to get a better understanding of mechanics.
Essentially, the top part is stuck in the bottom part because of the triangles on the side. It rests on a high tension spring, so that the spring absorbs some of the shock from landing, but doesn't fold in.
Any advice on this? If it comes to anything I might try entering it in a science fair, but I'm not sure. Mainly I want the experience, so thanks for any advice!

 

[sophiecentaur]

How would a runner with a prosthetic leg have a ball of his foot' on that leg?
Your diagram of a design using coli springs is testimony to the advantage of the leaf springs that many amputees use these days. They can be made with very good lateral stability whereas a coil spring always needs some sort of guide to provide the same stability.

 

[Thundagere]

Not on that leg. The article I was reading stated:

It has a custom, carbon-framed socket that attaches to his thigh, a metal knee and curving piece of plastic that acts as a foot with no heel, so Alan can run on his toes.

But the thing is, when you're forced to run on your toes it can harm your tendon. I'm wondering how one could create a prosthesis resulting in running "heel—toe" because while less efficient, it puts less stress on the tendon.

 

[sophiecentaur]

If this design is specifically for running then why not use blades on both legs? Plenty of able bodied people run around on blades and they seem to get on fine with practice.

 

[Thundagere]

If you're only missing one leg, then how would you put blades on both? It would unbalance you while running.
Also, can you elaborate on how leaf springs are used in prostheses? It sounds pretty interesting!

 

[sophiecentaur]

It would not be hard to balance the two blades, any more than to match a coil spring arrangement to a regular leg. Of course the two blades would need to be matched to the user - which could take a bit of time and effort. Else he would tend to run in circles. But this is all a known art. Just Google Running Blades.

There was recently a complaint that a double amputee should not be allowed to compete against regular runners because of the 'advantage' the blades gave him!

 

[Thundagere]

So what you're saying is that one person can have one real leg, with the other amputated, and still run with two legs?
Do you think this project is still worth doing, or should I try something else?

 

[mazinse]

this looks more like engineering than actually physical biology etc etc. Is that something you are into

 

[Thundagere]

Yeah, it is. I actually posted this in the general physics section, but it was moved. Sort of like a crossover of engineering and medical sciences? Either way, I was hoping that someone could give me more info on this.