Lifting your feet higher costs LESS energy when running

by not lifting my feet so much but keep them close to the ground I save a lot of energy yes I get it it makes so much sense it must obviously cost more energy to lift your feet and knees more when you run then do it less just like it takes more energy for me to lift my arm like this compared to not lifting the arm if I don't lift my arm no energy is used at all seems much better than wasting muscle power on a lift right this is a common mistake when talking about running technique you compare how it works when you're standing still with what happens when you're in motion like when you're running we can start by looking at how the law of physics work a long pendulum oral lever costs more energy to move than a shorter pendulum or a liver this works much like an old-fashioned metronome when the weight is placed at the top you get a long pendulum that moves slowly and when you move the weight down to make the pendulum shorter it goes faster this is very clear also in figure skating if you hold your arms out from your body when you do a pirate and spin and turn around it goes slow whereas the period is quite fast when you bring your hands and arms closer to your Central Mass if the foot comes up a little bit more the foot moves closer to your center of mass which makes it easier and costs less energy than if the foot moves closer to the ground [Music] thank you and there are actually several other things that makes a slightly higher foot contribute to your running costs less energy such as a mechanical push of the tibia that will contribute to a better knee drive and a better utilization of the rubber band effect you get from the stretch shortening cycle as well as several other factors but now you might think that lifting your feet and knees still costs more energy than what you save through the shorter levers the movements closer to the center of mass and the mechanical assistance and all the rest but it's not at all about actively lifting your feet and knees instead it's all about relaxation and letting the foot kind of just dangle up you relax it and it will swing up it's all about relaxation do I have any proof that it works like this yes of course I do with my 3D cameras I can measure how much energy it takes to move your body parts when you run note that I'm now talking not at all about moving the body up and down but only the energy it takes to move the arms and the legs in relation to your Central Mass adjusted to tests one where I did not lift my feet and knees so much but I just let my feet move quite close to the ground on the way forward and backwards and one when I did the relaxation thing note the relaxation that makes my feet swing up by themselves and now I put these two tests to together the darker thinner lines is as you can see when I ran with my feet close to the ground while the thicker lighter lines is when I relaxed and left my foot swing up looking at these two figures it's easy to think that it costs more energy to move the body parts more that is the thicker lighter lines where I bring my foot up then we look at the bars that show how much energy was used to move my body parts the light colored bars to the left is showing when I let my feet come up and that bar is lower then the darker bar on the right which is where I had my feet close to the ground so the fade close to the ground costs more energy and this is a measurable fact but what about my Cadence since it costs more energy to move things fast compared to slow maybe I had a higher Cadence when I had my feet close to the ground and that's why it costs more energy I actually didn't think about my Cadence at all when I did the tests but it turns out that I had a little higher Cadence in one of the tests but if we look at the Cadence we can see that I had a slightly higher Cadence when the feet came up higher so I moved my legs both faster and in a bigger movement than when I relaxed my knees but the cost of moving my body parts was significantly lower it may sound so logical and like common sense to save energy by keeping your feet close to the ground but when you measure the cost of energy and know a bit about the law of physics it's quite easy to see that this is not the case the recent many recreational Runners have their feet too close to the ground is usually because they use their thigh muscles to prevent the movement some Runners because they think that having their feet close to the ground costs less energy and some are just bad at relaxing and then they put energy into resisting the movement which leads to costing more energy to move the foot and the leg forward again they spend energy to get a movement that costs even more energy it's like paying a monthly fee to a club to get a higher rent as opposed to not paying a monthly fee and get lower rent at least as long as you get the movement through relaxation and partly on how you move your hip and your core and you don't actually lift your feet with muscle Force there is a big difference between to do a movement to force it and to letting the movement happen just like you learn in my online course and of course I would like to add that exactly how high the foot and the knees should be depends very much on how fast you run the faster the pace the bigger the movement and as always you do what you want if you like to have your feet close to the ground when you run I think you should have your feet close to the ground when you run I don't care I'm just here to tell you how the biomechanics of running works I truly hope you liked that video and if you did please click the like button and maybe also the Subscribe button and feel free to check out all the other content I have here on my channel and maybe you are also interested in my online course you'll find it at fredexilen.com

Channel: Fredrik Zillén - Running Technique Specialist

Views: 1,671,710

Keywords: running, running technique, running shoes, trailrunning, trail, running biomechanics

Id: Jj9ZgQgQvBk

Length: 7min 46sec (466 seconds)

Published: Thu Apr 13 2023