Stairs that give you a leg up!

Scientists in the US have come up with a set of steps which store the energy you expend when you descend, and then give you a helpful “leg up” when you go up again.
18 July 2017

Interview with 

Professor Lena Ting, Georgia Tech College of Engineering and Emory University of Medicine


As we get older, climbing stairs can become more challenging, and installing a lift isn’t always practical or affordable. Now scientists in the US have come up with a set of steps - that you can retro-fit over your existing staircase - and which store the energy you expend when you descend, and then give you a helpful “leg up” when you go up again… Katie Haylor got a spring in her step hearing how it works from Lena Ting from Georgia Tech College of Engineering and Emory University of Medicine...

Lena - So we start at the top of the stairs and each of the treads move up and down, just the height of one stair. And when you step down, the stair starts at the same height as the floor that you're on and as it accepts your weight, it slowly lowers, stretching some springs. So, it cushions your descent of the stairs and actually reduces the amount of work that your muscles need to do and, actually, makes it quite soft and pleasant to go down.

Katie - So the energy is being stored in the spring, right?

Lena - That’s right. So, you're using your own power to stretch the springs. When the tread lowers by one-stair height then it gets locked in. And so now, we’ve locked in that energy into a stretched spring, and you go down a series of stairs, and the stair treads get locked. When you turn around and you want to go back up the stairs, now the energy is stored in each step and we have some simple pressure sensors on each tread that senses when you put down one foot and when you put the next foot on the higher tread, it releases the back tread, and that gives your back leg a little push up.

Katie - Okay, so the energy is being stored on the way down and it’s being used on the way up to give you a little boost just to help you get back up the stairs.

Lena - That’s right and we found that that boost to what we call the trailing leg reduces the amount of work done at the knee of the leading leg by about 37 per cent.

Katie - Okay, so that’s the energy being saved in a sense I guess by going up the stairs, but what about going down the stairs? Does it have any benefit there?

Lena - What was surprising is that the amount of work going down which is generally used to break the body to keep us from falling against the pull of gravity, also decreased by about 27 per cent in the ankle. So it’s energy that’s dissipated and the stairs work on a principle by helping you do the breaking, so you use less energy. But then we also store that energy so that it can be used going back up.

Katie - Ultimately, why is this invention important?

Lena - Well, I think we all know, people who have difficulty walking up and down the stairs, either because they're ageing or even have a temporary injury such as knee surgery. These allow people to climb existing stairs that are very difficult to retrofit or you might not want to retrofit them. It also allows people to take advantage of the mobility that they have. So, if you're able to partially walk up and down the stairs then this can keep people active, independent and living in their own homes.

Katie - So it sounds like these stairs would give people who can do a bit of exercise, that freedom still to move around and not be confined to – like you said – a lift chair or something.

Lena - Participating in going up and down the stairs is very important for maintaining the mobility that somebody has. If they were to start using the chair lift then because our mobility is ‘use it or lose it’ then their motor ability may in fact degrade faster. It’s extremely important that we keep active and maintain independence as people age.


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