3 ms·

Haven’t similar devices been around for ages https://en.m.wikipedia.org/wiki/Jumping_stilts https://en.m.wikipedia.org/wiki/Jumping_stilts

DropPanda 3y ago
No, the article specifically talks about a device where the legs perform work continuously, as in cycling. The device you linked to only lets the legs work during ground contact.
tech_ken 3y ago
No, the difference is when/how you load the springs. This proposal seems to be that you load the spring with your leg in the air before it makes contact with the ground (achieved by attaching the top of the spring up the leg), then land the loaded spring and unload. Their argument is that this allows for higher overall energy output from the human body (akin to cycling). In a jumping stilt you're loading the spring when you put your foot on the ground and unloading immediately, so the energy output only really occurs during that period of foot contact, which presumably lowers overall output.
- culebron21 3y ago
  You do the same in jumping stilts. You move arms and body in the air to increase jump amplitude, and land on a straight leg to compress the stilt and let it bounce back. If you try working with hips/knees while touching the ground, you'll amortize all the energy you generated, and exhaust quickly. Beginners suffer from this, and it takes some learning to run properly. Also, the energy converts from motion into spring load and back into motion, and you can keep adding it. Pro stilt jumpers can jump several times with more and more energy and increase height. When I took such classes of spring stilts, the coach showed us jumping above 2.5 m. Me and a classmate held a ribbon in our hands above our heads (we stood in stilts too), and he jumped several times towards us, each time higher, and finally flew above the ribbon. This is actually much more work than olympic jumping, where the COG of the jumper is actually a bit lower than the bar. This guy had to jump with COG much higher than the ribbon. But as I mention in the other post, if you fall down even routinely while running on stilts, it's very painful -- falling forward with your arms extended ahead, you still hit the ground with the ribs. Then they ache a month.
- culebron21 3y ago
  Actually, you're right, now I recall it better, you swing arms in the bottom point, to compress the spring better. Waving arms in the air does not help.
  - tech_ken 3y ago
    Regardless of when you swing your arms, by doing so you're introducing additional energy into the system so is kind of beside the point. The relevant comparison (in the context of their paper) is how fast you can convert chemical energy into kinetic through your gait, not how much chemical energy you can load into the springs. Jumping stilts are a 4-step cycle: 1a. LOAD (Foot-ground contact, foot is descending) 2a. UNLOAD (Foot-ground contact, foot is ascending, optionally arms swing to boost upward force) 3a. WAIT (No foot-ground contact, foot is ascending) 4a. WAIT (No foot-ground contact, foot is descending) Their proposal is 3-step: 1b. LOAD (No foot-ground contact, foot is descending) 2b. UNLOAD (Foot-ground contact, foot is ascending, optionally arms swing to boost upward force) 3b. WAIT(No foot-ground contact, foot is ascending) Step 1b performs the same function as both Steps 1a and 4a, but is closer to Step 4a alone in terms of duration. By reducing the overall time one cycle of gait takes you're able to convert the same amount of energy from chemical to kinetic in a shorter amount of time (ie. achieve a more powerful gait cycle). This presumes that you can achieve equivalent levels of energy input with both methods, but this doesn't seem like a huge reach to me since both methods rely on springs so presumably you could fiddle with the spring constants until the overall energetics are the same. It's kind of like how an 18-wheeler can produce tons of torque (which it needs to move something heavy), but has less horsepower than a Porsche. Torque is what determines how much weight you can haul (or in the case of jumping stilts, how high you can go), but horsepower is what determines how much time it takes to go from 0-60MPH. Swinging your arms is like adding more torque, but the paper is about maximizing horsepower.
    - culebron21 3y ago
      Ok, makes sense. But I wonder: if it's so hard to run in jumping stilts (which I know personally), does it make sense to make another device that can consume your muscle energy?
scotty79 3y ago
I think it's about having you being hanged in harness on the hips while you are running. This way you don't have to extend energy for your muscles to keep you upright. Springs do that. Then all the energy generated by your muscles can go towards creating motion.
oldbbsnickname 3y ago
Yep. I think I saw these on the TV show "Beyond 2000".
euroderf 3y ago
I guess these are about the same as "kangaroo shoes". I wonder, do these things add endurance ? Or do they maybe require the use of otherwise-little-used muscles, reducing endurance ?
culebron21 3y ago
I've used them for a year, and fell from them twice, the second time because a rubber shoe of the stilt broke apart, and strained a lot my knee. No broken bones, but it took a week to start cycling, then in 2 weeks I could walk almost normally, and it took whole 3 months to stop feeling the pain. I sold them after that. Running in them is VERY hard, even if you do it properly (landing on straight legs, to not dampen the energy). You can run only at high power mode, like sprint, for 200-300 metres.

DropPanda 3y ago

No, the article specifically talks about a device where the legs perform work continuously, as in cycling. The device you linked to only lets the legs work during ground contact.

tech_ken 3y ago

No, the difference is when/how you load the springs. This proposal seems to be that you load the spring with your leg in the air before it makes contact with the ground (achieved by attaching the top of the spring up the leg), then land the loaded spring and unload. Their argument is that this allows for higher overall energy output from the human body (akin to cycling). In a jumping stilt you're loading the spring when you put your foot on the ground and unloading immediately, so the energy output only really occurs during that period of foot contact, which presumably lowers overall output.

culebron21 3y ago
You do the same in jumping stilts. You move arms and body in the air to increase jump amplitude, and land on a straight leg to compress the stilt and let it bounce back. If you try working with hips/knees while touching the ground, you'll amortize all the energy you generated, and exhaust quickly. Beginners suffer from this, and it takes some learning to run properly. Also, the energy converts from motion into spring load and back into motion, and you can keep adding it. Pro stilt jumpers can jump several times with more and more energy and increase height. When I took such classes of spring stilts, the coach showed us jumping above 2.5 m. Me and a classmate held a ribbon in our hands above our heads (we stood in stilts too), and he jumped several times towards us, each time higher, and finally flew above the ribbon. This is actually much more work than olympic jumping, where the COG of the jumper is actually a bit lower than the bar. This guy had to jump with COG much higher than the ribbon. But as I mention in the other post, if you fall down even routinely while running on stilts, it's very painful -- falling forward with your arms extended ahead, you still hit the ground with the ribs. Then they ache a month.
culebron21 3y ago
Actually, you're right, now I recall it better, you swing arms in the bottom point, to compress the spring better. Waving arms in the air does not help.
- tech_ken 3y ago
  Regardless of when you swing your arms, by doing so you're introducing additional energy into the system so is kind of beside the point. The relevant comparison (in the context of their paper) is how fast you can convert chemical energy into kinetic through your gait, not how much chemical energy you can load into the springs. Jumping stilts are a 4-step cycle: 1a. LOAD (Foot-ground contact, foot is descending) 2a. UNLOAD (Foot-ground contact, foot is ascending, optionally arms swing to boost upward force) 3a. WAIT (No foot-ground contact, foot is ascending) 4a. WAIT (No foot-ground contact, foot is descending) Their proposal is 3-step: 1b. LOAD (No foot-ground contact, foot is descending) 2b. UNLOAD (Foot-ground contact, foot is ascending, optionally arms swing to boost upward force) 3b. WAIT(No foot-ground contact, foot is ascending) Step 1b performs the same function as both Steps 1a and 4a, but is closer to Step 4a alone in terms of duration. By reducing the overall time one cycle of gait takes you're able to convert the same amount of energy from chemical to kinetic in a shorter amount of time (ie. achieve a more powerful gait cycle). This presumes that you can achieve equivalent levels of energy input with both methods, but this doesn't seem like a huge reach to me since both methods rely on springs so presumably you could fiddle with the spring constants until the overall energetics are the same. It's kind of like how an 18-wheeler can produce tons of torque (which it needs to move something heavy), but has less horsepower than a Porsche. Torque is what determines how much weight you can haul (or in the case of jumping stilts, how high you can go), but horsepower is what determines how much time it takes to go from 0-60MPH. Swinging your arms is like adding more torque, but the paper is about maximizing horsepower.
  - culebron21 3y ago
    Ok, makes sense. But I wonder: if it's so hard to run in jumping stilts (which I know personally), does it make sense to make another device that can consume your muscle energy?

scotty79 3y ago

I think it's about having you being hanged in harness on the hips while you are running. This way you don't have to extend energy for your muscles to keep you upright. Springs do that. Then all the energy generated by your muscles can go towards creating motion.

oldbbsnickname 3y ago

Yep. I think I saw these on the TV show "Beyond 2000".

euroderf 3y ago

I guess these are about the same as "kangaroo shoes". I wonder, do these things add endurance ? Or do they maybe require the use of otherwise-little-used muscles, reducing endurance ?

culebron21 3y ago

I've used them for a year, and fell from them twice, the second time because a rubber shoe of the stilt broke apart, and strained a lot my knee. No broken bones, but it took a week to start cycling, then in 2 weeks I could walk almost normally, and it took whole 3 months to stop feeling the pain. I sold them after that. Running in them is VERY hard, even if you do it properly (landing on straight legs, to not dampen the energy). You can run only at high power mode, like sprint, for 200-300 metres.