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Another interesting idea was the use of pain symptoms as something to educate.. My achilles hurts. What does that say about how I am running?.
It says you need to change your form to reduce the ankle plantarflexion moments....and Chi running does not do that. If you had achilles tendon problems and were forefoot striking, and the achilles got better, then it had nothing to do with the 'running form' and everything to do with either a big coincidence or progressive overload adapting the tissues.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
It's so cool, I'll post it again. In this race who had the best "form"? Johnson, obviously. Who had the second best "form"? The guy in 2nd, obviously. Who had the 3rd best "form"... etc, etc. So, we might conclude from this that whoever wins a race has the best "form" in that race and the guy in 2nd had the second best "form" in that race, etc. Note how the "form" of these individuals is different in the photo below.
In another race, a guy leaning forward and rearfoot striking might be the winner, while the guy leaning back and forefoot striking might be in 2nd. What does this tell us? It tells us the "form" is not necessarily predictive of winning a race.
Now, lets build a multivariate model to see who will win the 100m at the olympics in London in a few week time. I'm guessing that all of the finalists will be forefoot strikers, so regardless of who wins, they will be a forefoot striker. So, strike position will not in any way differentiate the winner from the loser- agreed? Thus, strike position will not be a good predictor of speed over the 100m final, nor of the winner within this sample. Moreover, other factors will be much better predictors of winning within the model. Y'all understand? I understand that foot-strike position is only one element of the so called "form" of a runner, but it helps exemplify here.
"Form" for what though? Winning races? Isn't competitive running all about winning races? Or, avoiding injury? These may not be the same thing in terms of "form".
So, lets do it again and build a multivariate model to see who'll get injured during the finals of the 100m at the olympics. Again, I'm guessing that all of the finalists will be forefoot strikers, so regardless of who pulls up with an injury, they will be a forefoot striker. So, strike position will not in any way differentiate the injured from the uninjured- agreed? Thus, strike position will not be a good predictor of injury over 100m, within this sample. And other factors will prove to be much better predictors within the model.
It's just one of those funny sampling/ statistical things. And something to be aware of when reading research.
Finally, lets take our guy in 2nd place in the photo, lets say at the end of the race he found he'd strained his Achilles tendon. If we measured various characteristics of his "form"- forward lean of the torso, foot strike pattern etc and compared that to those of his rivals and built a model, we might conclude that his "form" predicted his injury. But what if he was the only one in the field of runners carrying the genetic marker for Achilles tendonosis, but we hadn't tested for this nor included it as a variable within our model? How do we differentiate the "form" from the genetic marker as the predisposition to injury? If we have known factors which are predictive of winning or getting injured, but don't include them in our model, other factors might seem to be important, when in reality they are not.
What if we could count the proportion of fast twitch fibres in all of Johnson's muscles and compare that to his fellow competitors here? Might that be a better predictor within the model to predict winning over the "form" variables?
As Bill Donaldson alluded to in another thread, and I don't want to get embroiled in this, what if we used skin colour as a predictor for finishing position in our picture here? Answer: it should probably be a better predictor of race position than "form". And if Christophe Lemaitre wins the 100m at the London olympics and we put skin colour into our model to predict the winner....... Y'all see what happens when the sample isn't well balanced in terms of a particular variable?
Sorry to burst all the white caucasian runners bubbles out there....... but your chances of winning at the 2012 Olympics are pretty slim, regardless of your running "form". Predictions anyone?
If only it was so simple as "form".
Excellent posting, Dr. Spooner.
"Chi Running", like its running-form counterparts, "Pose Running" and "Alexander Technique", are based on the idea that "natural running" does not involve heel-striking. The selling of these "new running forms" to recreational runers is only able to work as a business model because there are a great number of heel-striking recreational runners who want to become faster and become less injured and do not want to work very hard in order to get better or become less injured. These runners will do whatever is necessary, including buying a book, taking a class, etc. so that they can to become better, faster and less injured.
Like Simon and Craig have plainly stated, "running form" is only one factor that may affect running injuries and running performance, but it is a relatively small factor. The current evidence points to the fact that heel striking may be the most metabolically efficient form of running for many individuals, especially at slower running speeds. People choose to heel-strike for a reason when running: heel-striking is likely metabolically more efficient than midfoot and/or forefoot striking running for slower running speeds. However, we don't know which "running form" produces the least injuries, and I suspect, that one type of "running form" will increase the risk of a certain subset of running injuries and another type of "running form" will increase the risk of another subset of running injuries.
In other words, there is no one best "running form" and the people who claim that there is one "best running form" for all people (i.e. Chi Running, Pose Running, Alexander Technique) are selling "snake oil" as far as I'm concerned, cashing in on the current fad that "running form" is much more important to becoming faster and becoming less injured than it really is. I'm sure in another decade that some other "secret formula" will be sold to runners to make them faster and less injured without having to work too hard for it.
Only one more vacation day left in the Scottish Highlands....went from thunder and lightning a little over an hour ago to warm sunshine now. Very nice country up here...and the sun sets up here currently at 10:16 PM!
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
That non-response to my question tells me everything I need to know.
You don't appear to know an awful lot about anything. Here's your starter for 10, Let G = Gravitation force acting through the centre of mass of the runner, how is this force pulling him forward? Answer it's not, it's attempting to pull him downward.
Lets add in some other forces: let GRF be the vertical ground reaction force. In this situation the force couple created by G and GRF should tend to create an anticlockwise rotation of the runner...
Now, rather than expecting to be told the answers and getting your arse in your hand when you don't get the answer you were looking for, try reading and studying a little.
Mr Spooner I dont often post anything on here but you have just made my day with your jpeg names.
I am still laughing and will probably giggle for the rest of the day.
In simple terms to sicknote what drives you forward is your body working with the ground reaction forces against gravity to bring your COM back into a more stable location so you wont fall over.
However, why all this debate on technique?
What is the correct technique for any one? It is dependant on a number of factors: genetics, biomechanics, fitness, strength, flexiblity and chosen speed at which your running.
If I was michael johnson and had his core, glute, hamstring and quad strength and could turn my legs round at the pace he could then i would be bombing around at that speed with that technique, but i am a fat boy so i can't.
If i decided that forefoot running was my thing, the amount of wasted energy i would be using up in vertical displacement (because i run so slow) i would have more chance winning a medal in dressage, prancing about like the horse.
When we the average fatboy decides to don a pair of running shoes we will transistion through a number of techniques as we get stronger, fitter and faster. To jump into to one technique because we are told that it is the way to go is foolish, listen to your body and go with what feels best and you will find you change as you go along.
i am pretty sure that this is one of the worst foot strike "over proantion" videos i have seen and his arm swing technique is pretty shoddy to, but the boy has done pretty well for himself.
So what is pulling my body forwards more, if not gravity?, having implemented a greater lean angle.
It may be the force of friction pushing you forward. I don't recall seeing a paper that has done the calculations of running. In walking, Winter showed that there is a trade off in energy between potential and kinetic energy. There is forward momentum in double support. As the trailing limb lifts, the center of mass is behind the stance limb and this creates a force couple (gravity and ground reaction force) that will tend to rotate the body backward. This moment slows the forward progression and also the body pivots over the stance limb and rises to its highest point when the center of mass is over the stance limb. At this point the forward velocity is at its lowest (and kinetic energy is lowest), but potential energy, in the form of height is at its highest. When the center of mass moves anterior to the center of pressure there will be a force couple rotating the body forward, causing forward acceleration. (The pull of gravity is anterior to the center of pressure) The swing leg will move forward and start accepting weight and the body will have reached its lowest point and repeat.
It might just be a matter of semantics. When the body's center of mass is anterior to its center of pressure, you could say that gravity is pulling the body forward. However, at the same time, the posterior to anterior component of ground reaction force is increasing and this is pushing the body forward. If there were no friction at the foot ground interface, the foot would slide backward and the body would not be accelerated forward as much. So you can make a case for the ground pushing the body forward.
Now we can talk about forward body lean. It will help speed forward rotation as long as the center of mass is anterior to the center of pressure of ground reaction force. Forward body lean may not necessarily do this.
In sprinting, as opposed to jogging, the contact point of the foot at landing is more posterior in sprinting and more anterior in jogging. With this there will be less slowing of forward progression with each foot landing.
i am pretty sure that this is one of the worst foot strike "over proantion" videos i have seen and his arm swing technique is pretty shoddy to, but the boy has done pretty well for himself.
...which just confirms that there is no one best way to run....
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
It might just be a matter of semantics. When the body's center of mass is anterior to its center of pressure, you could say that gravity is pulling the body forward.
Nope, gravity is still tending to pull the body downwards, that is all it can ever do in isolation. The force couple of the ground reaction force with the gravitational force acting at the the centre of mass might tend to cause forward rotation of the segments which are superior to the centre of rotation in the situation, yet those inferior to it are being rotated backwards. In the absence of any other forces though, the body would just spin on the spot, without making forward progression. Thus, other forces are required to make forward progression, not just gravity and GRF. Gravity and GRF alone won't do it, unless you are descending an incline. Moreover, you have to get the centre of mass ahead of the centre of pressure and not fall over.
Nope, gravity is still tending to pull the body downwards, that is all it can ever do in isolation. The force couple of the ground reaction force with the gravitational force acting at the the centre of mass might tend to cause forward rotation of the segments which are superior to the centre of rotation in the situation you defined above. In the absence of any other forces though, the body would just spin on the the spot, without making forward progression in this situation. Thus, other forces are required to make forward progression, not just gravity. Gravity and GRF alone won't do it, unless you are descending an incline. Moreover, you have to get the centre of mass ahead of the centre of pressure, this might happen in the second half of stance as you are leaping off the ground during running, but it probably happens infrequently during the first half in gait, unless you are falling over.
If there were no gravity, and the body were leaned forward with the feet on the ground, then the body would not rotate forward. Therefore, when this case of no gravity causing no body rotation is contrasted to the case where there is gravity and body rotation forward does occur, one could say that gravity was at least partially responsible for the observation that leaning forward on Earth will cause the body to rotate forward.
Gravity is responsible for the acceleration of the center of mass of the body which creates the ground reaction force (GRF) acting on the plantar foot. In turn, this GRF, along with friction between the plantar foot and the ground, causes a rotational force that causes an angular acceleration of the center of mass forward when the center of pressure acting on the plantar foot is posterior a line vertically downward from the body's center of mass, which David Winter called "center of gravity" (Winter, David A.: A.B.C. (Anatomy, Biomechanics and Control) of Balance During Standing and Walking. Waterloo Biomechanics, Waterloo, Ontario, Canada, 1995).
Therefore, to say that gravity is not responsible for the body rotating forward when one leans forward is not correct, but to say that gravity is partially responsible for the body rotating forward when one leans forward is correct.
I feel like I am back to the "walking on ice" debate I had with Howard Dananberg and Bruce Willams from years ago.
Here is a nearly identical thread from 5 years ago where we were talking about the same concepts.
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
If there were no gravity, and the body were leaned forward with the feet on the ground, then the body would not rotate forward. Therefore, when this case of no gravity causing no body rotation is contrasted to the case where there is gravity and body rotation forward does occur, one could say that gravity was at least partially responsible for the observation that leaning forward on Earth will cause the body to rotate forward.
Gravity is responsible for the acceleration of the center of mass of the body which creates the ground reaction force (GRF) acting on the plantar foot. In turn, this GRF, along with friction between the plantar foot and the ground, causes a rotational force that causes an angular acceleration of the center of mass forward when the center of pressure acting on the plantar foot is posterior a line vertically downward from the body's center of mass, which David Winter called "center of gravity" (Winter, David A.: A.B.C. (Anatomy, Biomechanics and Control) of Balance During Standing and Walking. Waterloo Biomechanics, Waterloo, Ontario, Canada, 1995).
Therefore, to say that gravity is not responsible for the body rotating forward when one leans forward is not correct, but to say that gravity is partially responsible for the body rotating forward when one leans forward is correct.
I feel like I am back to the "walking on ice" debate I had with Howard Dananberg and Bruce Willams from year ago again.
Why not turn your example around and assume the only force was gravity? Would this "pull the body forward" as "Sicknote" maintained"? I have no problem with gravity + GRF causing rotation. I do have a problem with gravity "pulling" the body forward; gravity, in isolation acts downwards end of story, hence it cannot pull the body forward. And for as much of the body that it pulls forward, it pulls some of it backward. As we have already demonstrated, gravity + ground reaction force will only cause a "forward rotation" moment of the superior segments if the centre of mass is ahead of the centre of pressure. If the centre of pressure is ahead of the centre of mass, then gravity + ground reaction force will create a "backwards rotation" moment on the superior segments. Either of these situations in isolation create spinning on the spot. Thus, something else has to drive the body forward linearly during running. It is friction which enables forward movement of the spinning object, as you note. Hence I was trying to get "sicknote" to add in the forces in diagram form.
So the question becomes, if the centre of mass was ahead of the centre of pressure at the time of strike during running, would you fall over onto your nose? Why not?
And in the second half of stance, during running gait, when the centre of mass is more likely to be ahead of the centre of pressure, the centre of mass is trying to rise upwards, hence gravity is working against this, so how is gravity "helping" here? How come those guys on the moon had such long strides?
Runners do not push off the ground but fall forwards via a gravitational torque.
Romanov N, Fletcher G.
Poses Tech Corp, Coral Gables, Florida, USA.
Link: http://www.ncbi.nlm.nih.gov/pubmed/17933203
Quote:
Abstract.
The relationship between the affect and timing of the four forces involved in running (gravity, ground reaction force, muscle force, and potential strain energy) is presented. These forces only increase horizontal acceleration of the centre of mass during stance but not flight. The current hierarchical models of running are critiqued because they do not show gravity, a constant force, in affect during stance. A new gravitational model of running is developed, which shows gravity as the motive force. Gravity is shown to cause a torque as the runner's centre of mass moves forward of the support foot. Ground reaction force is not a motive force but operates according to Newton's third law; therefore, the ground can only propel a runner forward in combination with muscle activity. However, leg and hip extensor muscles have consistently proven to be silent during leg extension (mid-terminal stance). Instead, high muscle-tendon forces at terminal stance suggest elastic recoil regains most of the centre of mass's height. Therefore, the only external motive force from mid-terminal stance is gravity via a gravitational torque, which causes a horizontal displacement. The aim of this paper is to establish a definitive biomechanical technique (Pose method) that is easily taught to runners (Romanov, 2002): falling forwards via a gravitational torque while pulling the support foot rapidly from the ground using the hamstring muscles.
Smells just like another illogical argument that is presented for the sole purpose of selling a certain style of running by the style's creator, Romanov.
I don't think the above is enough of a credible reason.
I don't think the above is enough of a credible reason.
...actually it is! I have sat through a couple of presentations from biomechanists (who know a lot more about this than me) in which they went through the biomechanical underpinnings used to promote Pose Running and showed that they were flawed. ...
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
Runners do not push off the ground but fall forwards via a gravitational torque.
Romanov N, Fletcher G.
Poses Tech Corp, Coral Gables, Florida, USA.
Link: http://www.ncbi.nlm.nih.gov/pubmed/17933203
Explain the findings of this study to us... Like you said Kevin, walking on ice all over again...
Like I said, about ten minutes ago: "And in the second half of stance, during running gait, when the centre of mass is more likely to be ahead of the centre of pressure, the centre of mass is trying to rise upwards, hence gravity is working against this, so how is gravity "helping" here? How come those guys on the moon had such long strides?"
And of course, Romanov had no vested interest here...
Here's a thought: gravity on earth is g = 9.81 m/s2, if we reduced the gravity to 8.81 m/s2 should we be able to run faster or slower? What about if we increased it to 10.81, faster or slower?
i think i am going to invent/start Chai running...
it's like normal running but with a cup of tea. (badum tish)
Before you start marketing it to the gullible, perhaps you should take Roberts course: Personal Improvement Starter Scheme ... it will help you become a real guru.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
Full quote from Eric: When the body's center of mass is anterior to its center of pressure, you could say that gravity is pulling the body forward. However, at the same time, the posterior to anterior component of ground reaction force is increasing and this is pushing the body forward. If there were no friction at the foot ground interface, the foot would slide backward and the body would not be accelerated forward as much. So you can make a case for the ground pushing the body forward.
This should read "pushing the body backwards" - right Eric?
When the center of mass is anterior to the center of pressure the gravity/ground reactive force couple will tend to rotate the top of the body forward. With no friction, the inferior segment would rotate backward. The inferior segment does not rotate backward because of the posterior to anterior force from the ground acting on the foot. This force is pushing the foot/body forward. When looking at walking this is corroborated by looking at anterior posterior ground reaction shear. When the center of mass is posterior to the center of pressure the a-p shear is posteriorly directed, ground acting on the foot, and when the center of mass is anterior to the center of pressure the a-p shear is anteriorly directed ground applied to foot. It's really important to label the forces at which force is acting on what. I didn't do that in original post.
In order to properly understand the biomechanics of running, it is far too simplistic to use only a static assessment of the center of mass (CoM) of the body relative to the center of pressure on the plantar foot as an assessment method of this dynamic weightbearing activity.
The first half of the support (stance) phase of constant velocity running involves a "braking action" of ground reaction force (GRF) pushing posteriorly on the plantar foot, while the second half of the support phase of running involves a "pushing forward" action of GRF pushing anteriorly on the plantar foot. During the support phase, there will be only one small instant in time when the GRF vector is vertically oriented, the whole rest of the support phase the GRF acting on the plantar foot will either be angulated posteriorly (first half of support phase) or angulated anteriorly (second half of support phase).
In addition, during acceleration of the CoM (e.g. in the first 5 seconds or so at the start of a race) or deceleration of the CoM (e.g. after the end of a race) during a running competetion, the position of the CoM relative to the CoP and the GRF vector will be signficantly different than during constant velocity running. Also, as running velocity increases (i.e. constant velocity running) for any given runner (i.e. running first a steady 7 min/mile pace, then running a steady 6 min/mile pace, then running a steady 5 min/mile pace) the magnitude of the GRF vector will increase, and as their running velocity decreases, the GRF magnitude will also correspondingly decrease.
Therefore, I hope that those following along do not make the mistake of assuming that one can accurately analyze still (i.e. static) photos of runners in a race or during running training activities to get any idea of the dynamics of running regarding the direction of the GRF vector, its spatial relationship to the spatial location of the CoM and the anterior-posterior shearing forces acting on the plantar foot at any instant in time during the support phase of running. Using still photographs to completely analyze the kinetics of running gait simply can not be done, however, still photography does allow to appreciate the kinematics of gait better.
Furthermore, to suggest that a forward body lean, such as is advocated by certain running style advocates, will make you run faster, better, or even with less injury is not only pure speculation with not a shred of credible scientific evidence to back this assumption, but such speculative ideas totally ignore the large body of research in running biomechanics that has been done over the past four decades.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
In order to properly understand the biomechanics of running, it is far too simplistic to use only a static assessment of the center of mass (CoM) of the body relative to the center of pressure on the plantar foot as an assessment method of this dynamic weightbearing activity.
The first half of the support (stance) phase of constant velocity running involves a "braking action" of ground reaction force (GRF) pushing posteriorly on the plantar foot, while the second half of the support phase of running involves a "pushing forward" action of GRF pushing anteriorly on the plantar foot. During the support phase, there will be only one small instant in time when the GRF vector is vertically oriented, the whole rest of the support phase the GRF acting on the plantar foot will either be angulated posteriorly (first half of support phase) or angulated anteriorly (second half of support phase).
In addition, during acceleration of the CoM (e.g. in the first 5 seconds or so at the start of a race) or deceleration of the CoM (e.g. after the end of a race) during a running competetion, the position of the CoM relative to the CoP and the GRF vector will be signficantly different than during constant velocity running. Also, as running velocity increases (i.e. constant velocity running) for any given runner (i.e. running first a steady 7 min/mile pace, then running a steady 6 min/mile pace, then running a steady 5 min/mile pace) the magnitude of the GRF vector will increase, and as their running velocity decreases, the GRF magnitude will also correspondingly decrease.
Therefore, I hope that those following along do not make the mistake of assuming that one can accurately analyze still (i.e. static) photos of runners in a race or during running training activities to get any idea of the dynamics of running regarding the direction of the GRF vector, its spatial relationship to the spatial location of the CoM and the anterior-posterior shearing forces acting on the plantar foot at any instant in time during the support phase of running. Using still photographs to completely analyze the kinetics of running gait simply can not be done, however, still photography does allow to appreciate the kinematics of gait better.
Furthermore, to suggest that a forward body lean, such as is advocated by certain running style advocates, will make you run faster, better, or even with less injury is not only pure speculation with not a shred of credible scientific evidence to back this assumption, but such speculative ideas totally ignore the large body of research in running biomechanics that has been done over the past four decades.
Quasi- static analysis. As long as we add in and label all the forces wheres the problem? Seriously though, I just used the photo to exemplify a point, it wasn't supposed to be a full kinetic analysis. That said, a photograph of the runner moving over a force plate should provide a reasonable 2 dimensional analysis.
In order to properly understand the biomechanics of running, it is far too simplistic to use only a static assessment of the center of mass (CoM) of the body relative to the center of pressure on the plantar foot as an assessment method of this dynamic weightbearing activity.
I would agree that it is simplistic, but not far too simplistic. You just have to know the limitations of your model.
Quote:
Originally Posted by Kevin Kirby
The first half of the support (stance) phase of constant velocity running involves a "braking action" of ground reaction force (GRF) pushing posteriorly on the plantar foot, while the second half of the support phase of running involves a "pushing forward" action of GRF pushing anteriorly on the plantar foot. During the support phase, there will be only one small instant in time when the GRF vector is vertically oriented, the whole rest of the support phase the GRF acting on the plantar foot will either be angulated posteriorly (first half of support phase) or angulated anteriorly (second half of support phase).
You very accurately describe the limitations of the static model. If you know the anterior component and the vertical component then you can add them in to make the model more accurate.
I have no problem with sagittal plane quasi-static analyses of a dynamic activity such as running as long there is sufficient data to make a meaningful kinetic analysis. My point was that knowing where the center of mass of the body (CoM) is relative to the support phase foot in a dynamic activity such as running tells us very little, if anything, about the relative position of the CoM to the GRF vector during that instant of the running activity (i.e. dropping a plumb line from the CoM to the foot certainly doesn't tell us whether there is a posterior or anterior shearing component to the GRF vector in a photograph of a runner).
However, if you were to draw the GRF vector relative to the plantar foot and the CoM in such a photo of a runner, then we could make some more meaningful conclusions regarding the forces and moments acting on the plantar foot and other joints axes of the foot and lower extremity and whether that runner's CoM was likely being accelerated or decelerated by the GRF vector.
Currently back in the good ol' USA...at Dulles Int'l Airport in Washington, DC. Home sweet....my own bed tonight!!
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
If we think about the passive dynamic walker challange discussed in this thread- http://www.podiatry-arena.com/podiat...ad.php?t=79426 we have eccentially created a situation where gravity is the only force causing forward motion (if we ignore the little tap you give it to start!).
However, for these machines to achieve sustained forward momentum you need a continuously decending slope. These machines don't work uphill, or on a flat surface. They technically do use gravity alone to propell them forwards.
Human bipedal locomotion however can occur on flat surfaces and even up hills! I've seen it with my own eyes.
My hypothesis is this (correct me if i'm wrong)- Gravity can only "pull you forward" if you are heading down a hill. (not counting falling over, which will technically "pulll you forward", but only as far as you can fall.)
I believe this is always true, whether you are a passive dynamic walking machine or a bipedal human with fancy joints and muscles and stuff. However, if you're on a flat or inclined surface, gravity will either pull you into the ground, or backwards down the hill. And if you're a bipedal human with muscles and stuff, now would be a good time to use them.
__________________
Phil Marshman
Mackay, Queensland Australia
If we think about the passive dynamic walker challange discussed in this thread- http://www.podiatry-arena.com/podiat...ad.php?t=79426 we have eccentially created a situation where gravity is the only force causing forward motion (if we ignore the little tap you give it to start!).
However, for these machines to achieve sustained forward momentum you need a continuously decending slope. These machines don't work uphill, or on a flat surface. They technically do use gravity alone to propell them forwards.
Human bipedal locomotion however can occur on flat surfaces and even up hills! I've seen it with my own eyes.
My hypothesis is this (correct me if i'm wrong)- Gravity can only "pull you forward" if you are heading down a hill. (not counting falling over, which will technically "pulll you forward", but only as far as you can fall.)
I believe this is always true, whether you are a passive dynamic walking machine or a bipedal human with fancy joints and muscles and stuff. However, if you're on a flat or inclined surface, gravity will either pull you into the ground, or backwards down the hill. And if you're a bipedal human with muscles and stuff, now would be a good time to use them.
Yep, I didn't start that thread randomly. As I said:
Quote:
Originally Posted by Simon Spooner
Thus, other forces are required to make forward progression, not just gravity and GRF. Gravity and GRF alone won't do it, unless you are descending an incline.
What about building a walker, Phil- you getting involved?
Just look at the picture here: http://biomechanics.byu.edu/footstrikesmens10k.jpg
The are the finalists in the mens 10k at the USA Olympic Trials - look at all the different foot strike patterns ... they are the best of best ... the elite .... is anyone going to try and convince people that one running form is better than another? (...even I was surprised at how many are heel striking at that speed!)
Just a follow up on this.
Have a look at the first two finishers in the Womens marathon @ London (esp the one in second place at the finish line):
How many of the guru's would want to try and change there 'form'? .... these runners are the best of the best ... just confirms there is no one best way to run.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
Re: Chi Running
As I said:
Linear Mode
