Step Frequency, Clinical estimate of leg stiffness left/right differences

Re: Barefoot Running Debate

I thank you.

Here's a little experiment that anyone can try:

Draw a cross on the floor.
Weigh yourself in Kg
flip a coin left is heads right is tails
Now hop on the spot using the cross as a target on the leg that the coin selected, count the number of hops over a period of 30 seconds

Take a break then repeat with the hopping with the other leg

Calculate the stiffness for each leg:
K = 40 x SF2 x mass

Where:
K is the leg stiffness (N/m)
40 is (2x∏)2
SF is the step frequency (steps per second)
Mass is measured in Kg

So divide the number of hops you did in 30 seconds by 30 to get your step frequency, square this and multiply by 40 and your weight.

Let me know if it is the same for both legs.

 

Re: Barefoot Running Debate

n =1 not the same for both legs

 

Re: Barefoot Running Debate

What stiffness values (k) did you get for left and right Mike? Which side is your dominant foot?

Here's mine:
Left 15888.53 N/m
Right 11610.53 N/m

I'm left handed /footed.

 

Re: Barefoot Running Debate

K Left = 512160
Right = 535440 n/m

and by dominant you mean which leg do I hop off if jumping which is left. Bbut if you mean kicking sports right.

Then for the next

Left 18779.2 n/m

Right 20525.2 n/m

 

Re: Barefoot Running Debate

Those second set of numbers you as well or someone else? Which hand do you write with?

I managed to get mine symmetrical on a re-test with 63 hops in 30 seconds on both legs giving 63/30 = 2.1 hops per second.
2.1 x 2.1 = 4.41. 4.41 x 40 =176.4. 176.4 x 93Kg = 16405.2 N/m

I think that's right (the units may not be)

 

Re: Barefoot Running Debate

I write with my right.


So divide the number of hops you did in 30 seconds by 30 to get your step frequency, square this and multiply by 40 and your weight.


Left 18779.2 n/m

Right 20525.2 n/m

when I saw your post I thought I might have got a bit messed up SF2 I did step freq * 2 , not divide sorry, the answers above are correct.


But what do these numbers 18779.2 newtons/meter and 20525.2 newtons/meter represent when looking at your numbers ?

 

Re: Barefoot Running Debate

It means you have a higher leg stiffness than me.

 

Re: Barefoot Running Debate

Here's me:

Right handed
Left footed

Coin toss dictated testing Left side first

Left = 15,260.4 N/m
Right = 20,250.0 N/m

 

Re: Barefoot Running Debate

Thanks Ian. Anyone else? Interesting we all seem to have a stiffer leg on the side corresponding to our writing hand.

So, if these left and right difference are real and can be extrapolated to running, in order to maintain a smooth centre of mass pathway, we would need to modulate the leg stiffness of one or both legs such that they are roughly equal, we might be able to achieve this by changing the step length on one side or the other, or both. Are there observable left to right step length differences in running?

 

Re: Barefoot Running Debate

I've just realised we are in the barefoot running thread! I reckon the last 20 posts at least would be better off here: http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=51623

Maybe Admin will do the honours...

 

Re: Barefoot Running Debate

Maybe a new thread please Craig on clinical estimate of leg stiffness left /right differences?

 

Re: Barefoot Running Debate

Something thats Ive been rolling around in the old brain - Don´t we need to consider Hookes law about spring length ?

ie Ian and Simon do you have a LLD - if so which side ( without starting a discussion and LLD measurments)

ps Ive got folks comming over on the weekend and we will go and watch the Bolt, Gay show down (Powell has dropped out) I´m thinking I might do so leg stiffness measurments with them as Simon has suggested we do today, but add LLD measurment and barefoot on grass and hard surface to see if there is any difference, maybe.

 

Re: Barefoot Running Debate

I do Mike. I'm "reliably" told my left leg is shorter

 

Re: Barefoot Running Debate

So we have a shorter spring on the left side.

Your left side is less stiff than the right.'
and your mass is the same.

As far as I can tell Hookes law is all about the force of the spring being equal and opposite to the force on the spring. In this case your mass.

So if the mass in the same, will it compress the left side more or less than the right, because of the shorter spring ?

In our hoping we got the centre of mass to move up and down at our bodies choosen frequency.

The right side more than the left - ie higher leg stiffness in your case right side than left.

has the shorter spring on the left affected this ? and does the difference in spring length and associated leg stiffness difference mean that the COM will move up and down in a constant and stabile manor whether left or right side is in contact with the ground.

or ?

 

Re: Barefoot Running Debate

Here's another thing to throw into the mixer: How about the neuro-muscular control differences between each side?

Personally I felt far more coordinated hopping on my right leg than I did my left - and this may be the reason I achieved 10 more hops in the 30 second time frame (75 on right vs 65 on left).

Why am I happier on my right side than my left? Because I played football for over 20 years and am left footed perhaps?

 

Re: Barefoot Running Debate

Ive just watched the 1st 10 min of the lecture but it seems very good and easyish to understand.

It from M.I.T and deals with Hookes law and simple Harmonic motion.

Hope it helps it seems to be helping me and anyone who lectures with a banana on their shirt is allright by me.

MIT hookes law and simple-harmonic motion

 

Re: Barefoot Running Debate

How about a banana poking out of their trousers/zipper?

 

Re: Barefoot Running Debate

just watched up to 25 min and my above ramble well was a ramble if Hooke law in an ideal spring is seen in this concept of leg stiffness. The movement of the COM should be the same.
But is the leg an ideal spring - brain meltdown

For anyone who thinks it´s a MIT run, run, run away the maths is confusing abit but the example are great- back to the video.

ps Ian I´ll leave that one alone

 

Re: Barefoot Running Debate

The 180 steps per minute or the 174 steps measured in the Hunter/Smith study is the optimized step frequency that minimizes oxygen uptake or metabolic cost. I guess round and round and round implies aerobic running. When running the 100, 200 or even 400 meters, the last thing the runners are concerned with is minimizing oxygen uptake or metabolic cost. Their energy production is anaerobic not aerobic so there step rate can't be compared to a rate that optimizes aerobic running. A runner can maintain 174 or 180 steps for hours while Simon can goes on holiday. I would think that Bolt's step rate would decline dramatically over the next few seconds if he continued to run at 256.8 steps per minute.

In addition to the Hunter/Smith study, running coaches such as Jack Daniels have found that there is a tendency towards 180 steps/min if you want to optimize aerobic efficiency. I would presume if you give or take 10 steps from 180, that would cover most individual differences. Even for the 10K, a good share of that race is run beyond the anaerobic threshold so you can throw the 180 out the window.

Dana

 

Re: Barefoot Running Debate

There is a big difference between the kinematics and kinetics and metabolic requirements of running a 100 meter sprint, running a 5,000 meter race and running a 100 mile race. In order to have an intelligent discussion on leg stiffness and running, the type of running you are talking about and the approximate speed of running should first be specified since sprinting is very different from the survival stride that many ultramarathon runners choose.

In addition, the metabolic requirements of sprinting and distance running are quite different also. In sprinting, the majority of the energy consumed by muscular effort during the event is anaerobic, with rapid accumulations of lactic acid occurring toward the end of the race due to the metabolic rate being higher than the oxygen metabolized which results in the athlete needing to have an increased respiratory frequency and respiratory volume after the race is completed to make up the "oxygen debt". However, in a 100 mile race, nearly all the energy consumed by muscular effort during the event is aerobic, with the amount of oxygen being metabolized being nearly equal to the amount of energy being used by the body using aerobic pathways, with little oxygen debt and little lactic acid accumulation. The faster the run, the more that glucose is burned and the less fat is burned. The slower the run, the more fat is burned, and the less glucose is burned. Exercise physiology 101.

 

Re: Barefoot Running Debate

Kevin and Dana, I agree and this was exactly the point I was making. So when I read a statement that says:

Stride rates for all events, for both men and women, fell between 185 and 200 steps per minute.

I point to evidence which questions this. I doubt very much that stride rates "for all events" fell between 185 and 200 steps per minute. I think this is completely over-stated. It may apply to aerobic events, but not anaerobic.

I can't find any data published in a scientific journal by Jack Daniels. I did find data which suggests a metabolic optimisation at about 174 steps per minute.

 

Re: Barefoot Running Debate

Mike and Ian, as you know we have been looking at the body today as a simple harmonic oscillator see here:
http://en.wikipedia.org/wiki/Simple_harmonic_motion

Note that period and frequency are independent of the amplitude and the initial phase of the motion.

Anyone else going to let us know their leg stiffness, those ageing knees playing you up too much to get involved, Kevin? what about you Dana? How symmetrical is your leg stiffness?

P.S. Mike, the leg isn't a spring at all, we're just modelling it that way- keep that in mind.

 

Re: Barefoot Running Debate

Sounds like someone trying too hard to me.

 

Re: Barefoot Running Debate

Sorry Simon, too much working and playing to do for now.

 

Re: Barefoot Running Debate

Your knees are playing you up then? :empathy: Shame as I was hoping to correlate leg stiffness with age Perhaps now would be a good time to shoot some hoop on your drive? Ask one of your staff to do it for you over lunch, you are paying their wages after all... You can blame me:butcher:.

Only joking, Kevin. But when you get the chance... I think this could form the basis of an interesting study for someone.

 

Re: Barefoot Running Debate

got carried away ........... who?, me?, never.

did you watch the M.I.T lecture? Goes over all that stuff as well. Helped me to see the experienments.

 

Re: Barefoot Running Debate

Not yet, but I will. What did you learn, Mike? Time for you to teach...

 

Re: Barefoot Running Debate

Here is mine,

I'm right handed and right footed.
I had 67 hops in 30 secs for both legs

Right = 17,594 N/m
Left = 17,594 N/m

I am 53.

Another thought I had that in spite of me hopping at the same rate on both legs, I do have slightly more wear on my left shoes than my right. If stiffness is similar, is it possible that I have slightly different leg lengths or the position of my left foot is a little different when landing? The additional wear is along the lateral heal surface so I suspect it is the result of landing vs toe off.

Dana

 

Re: Barefoot Running Debate

Nice symmetrical work Dana, now try it in your five fingers and then your most cushioned shoes.

 

Re: Barefoot Running Debate

I´m notsure about teaching, but a few things stood out.

* a change in mass will not effect a spring if operating within its stress zones, due the forces being equal and opposite. ie it will osselate at the same speed

* springs and penduliums will act very similar in the world of Physics which is very interesting in regard to our discussions about walking gait models.

* if the spring is working within it´s zones of stress the length of it should not effect of the mass on the spring as forces will always be equal and opposite. and will osselate at the same speed.

* my physics teachers at school had no idea how to teach.

* Kleg gets more and more interesting by the day.

I will watch it again tomorrow as some of the formula looked different to what we used today.

 

Re: Barefoot Running Debate

Simon, this put a smile on my face. Before I started, I was trying to decide whether to leave my Born sandals on or do it barefoot. I took one sandal off but put it back on because I felt stronger with it on. You do have my curiosity about the difference.

The other question I had was how high to jump each time. Higher jumps would mean lower a lower frequency, right? I also felt that once I did one leg which was my right one, I kind of had a goal for my left leg so I might have been biased.

What I found interesting is that I expected my right leg to be much stiffer than my left leg. I am right hand, right foot oriented and heavily favor both. When I ran track in high school and college, in addition to being a sprinter, I was a long jumper and triple jumper. I tried jumping from my left leg and the results where dismal. It might have had more to do with coordination than leg stiffness, though.

If I get a chance I will try testing my leg stiffness using Nike Vomeros (excessively cushioned) and vibrams. I'll also try to keep an bias from impacting my performance.

Dana

 

Re: Barefoot Running Debate

Keep low to the ground, thanks for playing. I'll explain later.

 

Re: Barefoot Running Debate

Simon, I kept low to the ground, just made sure there was complete clearance from the ground but not much more. My hop rate went from 67 to 81. Two things might be driving that, 1) I've had more practice and I'm getting better at it. 2) less time in the air, more time for hopping.

The 81 was the same for both legs as well as for the Vibrams vs the Nike Vomeros. An observation about Vibrams vs Nike, I did this on a concrete floor and with the Vibrams, the feedback was very clear. I knew exactly when my feet touched the floor and exactly when to push off. With the Nikes, is wasn't so clear. There was kind of a mush factor going on. There was some gray area between when I actually touched the floor and when the shoe was compressed to the point where I should push off. Ultimately, it didn't make any difference, the rate was the same.

The 81 hops for 30 seconds is starting to approach my running step rate of 88 for 30 seconds. I found it hard to keep up my counting at a rate of 2.7 count per second. It might have been more accurate if someone counted and watched the clock for me. My guess is with help and a little more practice I could get my rate up to 90 or close.

For 81 my numbers are:

Right = 25,792 N/m
Left = 25,792 N/m

If I hit 90, they would be: 31,842 N/m

The first set of numbers are light at 17,594 N/m for each leg.

Dana

 

Re: Barefoot Running Debate

So what conclusions might we draw from this?

1) the method employed is not sensitive enough to identify any differences in your leg stiffness between the two types of shoes.
2) there is no difference in your leg stiffness in the two types of shoes- what are the implications of this?

 

Re: Barefoot Running Debate

The thinking brain has taken over - The subject wanted to see a certain result and worked towards that result.

I´ve got 4 more data points but am waiting for Craig to break off into anew thread. Ive sent a PM.

 

Re: Barefoot Running Debate

Simon, with the difference between the two shoes, one being hard as a rock the other being a marshmellow, logic would say that there would be a difference in leg stiffness between the two shoes. Unless... bouncing an inch off the ground on your forefoot is not sensitive enough to identify differences, I don't know. Most of the cushion is in the heal area and that never touched the ground.

I would encourage you, Ian and Mike to try repeating the test for yourself first with cushioned shoes, then barefoot. Maybe you'll come up with different results, maybe not, I don't know.

I do know one thing, as I continue to run in Vibrams and collect Heart Rate data, my Heart Rate is consistently lower wearing Vibrams than wearing cushioned shoes. I know I'm conducting an experiment with n=1 but the difference is pretty profound. This morning my HR was 6 beats per minute less for the pace I was running than what I would have expected wearing traditional shoes. I don't know if it is possible to have that big of a difference in HR just based on the difference in weight of the shoe.

Dana

 

Re: Barefoot Running Debate

Mike, that is very possible yet I was expecting I would have many more hops using the vibrams than my marshmellow shoes. I was surprised by the results. When I run, I run consistently at 176 steps per minute in traditional shoes. I have counted this 100's of times, uphill, downhill, on trails, pavement at all different paces and it continues to come up at 176. When I wear Vibrams, the pace automatically shoots to 180. I expected the same difference when hopping on my basement floor, it didn't happen.

What might be helpful is to expand this beyond just my results. Try doing the test over with cushioned shoes and then barefoot, I'm curious if you come up with a difference.

Dana

 

Ok here 4 more people

barefoot hard floor-

right handed (RH) right - 12675 n/m Left - 15644.4 n/m
(RH) right - 9177.5 n/m Left - 11808.7 n/m
(RH) right - 17084 n/m Left - 19 360 n/m writes with right hand but kicks football with left

(RH) right - 11275.5 n/m Left - 13167 n/m

I noticed that the left is higher leg stiffness than the right with this family - I wondered after if it was because we started with the right side , or is does have some thing to do with as I an suggested the left side is more stable and used to being on the ground when kicking.

 

This maybe of interst-

They discuss the difference in right - left leg stiffness in 2 foot landing - Women more than men ?

https://uhra.herts.ac.uk/dspace/bitstream/2299/2986/1/Lower+limb+coordination+and+stiffness+during+landing+from+volleyball+block+jumps.pdf

 

right - 18 388 N/m ACL repair 35 years ago fat side
left - 21 852 N/m really bad medial O/A, the other side, fat also