Re: Mechanics of speed

March 6, 2009

For over 30 years I taught sports biomechanics in a university setting in

addition to approximately 5 to 10 years of teaching research. The

overriding principle in my classes was that the students had to explain what

took place in execution of a skill. It was not a mere description of what

occurred, they had to understand why it occurred and the role that it

played.

I had many students able to regurgitate a tremendous amount of information

from the book but if they could not explain it they still received an F. In

essence they had to know what occurred and they had to understand why and

how it occurred. If they could not explain it, they did not know it! This

was the defining element; they had to explain what they found, saw or

thought. If they could not, they did not understand it. In an explanation,

scientific facts are used to corroborate the explanation; it is not the

explanation.

Thus when I made my initial post - which I repeat below - about the

statements that appear to be thought of as " truths " I was hoping that most

readers would question what they read and not just except what they read.

Instead I got bombarded with the usual smorgasbord of bits of scientific

information that did not explain what occurred in producing horizontal

speed. At best it complicated matters.

You can rest assured that I will no longer attempt this as it appears that

most responders are in agreement with the nebulous terms being thrown out as

fact and explanation.

In this regard I have not seen a single statement showing proving or even

explaining how the ground reaction force is transferred to horizontal force

producing horizontal speed. I never said I disagreed with the production of

ground reaction force. This does occur and plays a valuable role in

running. But to say that this the only force involved that produces

horizontal speed has not been substantiated. They cannot do it because they

cannot explain how a vertical force produces horizontal speed.

We hear about the mass- spring model and Newton's laws of motion. But we do

not read about how they equate to producing horizontal speed. There are

studies showing that the ground reaction force as in the first part of the

mass -spring affect loads the leg muscles - mainly the Achilles' tendon

which is needed for ankle joint extension. But according to the proponents

of ground reaction forces being responsible for horizontal speed, ankle

joint extension does not play a role. While we do not hear about is the

release of the energy that is accumulated in the ground reaction force.

Keep in mind that the knee remains bent when the runner pushes off. There

is a minimal vertical component. But then I forgot, there is no pushoff

according to the locomotion experts. Everything just happens automatically

on touchdown.

When Newton's laws are tossed around it appears that the law of action -

reaction is ignored. In essence it means that for every force that is

applied in one direction there is an equal and opposite force applied.

Since Ken and others state that ground reaction force is produced by gravity

in a vertical direction the opposite force must be vertical. The runner

needs to exert a horizontally applied force directed in a backward direction

so that the reaction force will propel the body forward. But they show no

evidence for this.

In addition there has not been a single statement in in regard to what the

body does to generate ground reaction forces. It is somehow believed that

dropping down approximately 4-6 centimeters is all that is required to

propel a body forward. How the runner can generate force or more force

through actions of the arms or legs is completely ignored. They believe

that these movements are immaterial.

Science is used to simplify and explain what occurs in nature. This is why

I persisted in trying to have the proponents explain what they are

preaching. But as I saw previously and as I say now, the proponents of

ground reaction force being responsible for horizontal speed cannot explain

how this happens. If a coach repeat these statements to a runner - or even

a sixth grade student who are not strong in the sciences, do you believe

that he will know exactly what is happening in the running strideand how he

will be able to enhance his running?

I am truly saddened that instead of taking science to a higher level we see

it being bastardized to support unsupportable conclusions. As I used to say

in my classes, if you can't explain it you don't know it.

Following is the first post that I wrote:

I believe we should add one more conclusion to the general statements that

were made in this post.

The more the statement doesn't say anything the more believable it is and

the more impressed everyone is. This may seem like a harsh statement but it

is truly tiresome to keep hearing the same things that sound impressive but

nobody can explain.

For example if the underlying mechanical characteristic of elite sprinting

is " large mass-specific forces applied during brief foot -ground contact

times " how does one generate large mass specific forces? What actions must

the body execute to do this? I have never seen an answer to this.

Further on it is stated that " all info on terrestrial motion concludes the

same thing. Any changes in speed are the direct result of the ground

support forces. " In addition it is stated that " recovery of the swing leg

must be largely passive... " but yet, the swing leg goes from behind the body

to in front of the body in a fraction of a second. This is passive?

Someone should be able to explain it if this is true.

Still another-- if " the more force applied will result in longer stride

length and greater frequency " is true, how can more force at push off equate

to greater frequency? explain the mechanism involved.

Instead of repeating the same statements as though they are Gospel isn't it

about time we tried explaining what occurs. This is the only way to

understand what is happening. If I'm wrong please explain

Yessis, PhD

Professor Emeritus, CSUF

President, Sports Training Inc.

www.DrYessis.com <http://www.dryessis.com/>

CA, USA

March 7, 2009

Dr Yessis,

This is not a class, and the members of this list are not your students and

they are not here to be graded by you, and explain their knowledge.

In my humble opinion, if you wish to enlight the members over the mechanics of

running you should outline on the list punctually,

all the points you consider relevant to the subject (including the relevant

physics)

This would greatly:

1. Help the list to see your point

2. minimize the resistance to your idea which might be created by the " teacher'

attitude and the 'you must explain to me first " attitude

3. Help transfer your ideeas. Many ppl will not buy your books so they learn

how you think. From different reasons. But by explaining your position, and the

basic of physics, you might just create sufficient self interest in a person to

further his understanding and buy your work. This would work much better than

" buy my books " IMHO.

With respect

Dan Partelly

Oradea, Romania

>

> For over 30 years I taught sports biomechanics in a university setting in

> addition to approximately 5 to 10 years of teaching research. The

> overriding principle in my classes was that the students had to explain what

> took place in execution of a skill. It was not a mere description of what

> occurred, they had to understand why it occurred and the role that it

> played.

>

> I had many students able to regurgitate a tremendous amount of information

> from the book but if they could not explain it they still received an F. In

> essence they had to know what occurred and they had to understand why and

> how it occurred. If they could not explain it, they did not know it! This

> was the defining element; they had to explain what they found, saw or

> thought. If they could not, they did not understand it. In an explanation,

> scientific facts are used to corroborate the explanation; it is not the

> explanation.

>

March 8, 2009

Dan

I was very surprised at your post. You completely missed the point of what

I said. The philosophy I had in my classes is the same philosophy I use

when evaluating the research being done today as well as the " scientific "

comments being made on this forum and others. Perhaps that's the problem

with most scientific studies in this field. People just assume that

everything is correct because it is " a research study " . A true scientist

examines the study to see if it holds water. If it doesn't it is a poor

study and should be disregarded.

Instead of criticizing me and my " ideas " - which I have not posted -- why

don't you examine the statements being made that I'm questioning. As I've

said in just about every single post there are no explanations to show that

there is any understanding of what is being said. Thus, if they can't

explain it they don't know it. Their statements cannot be backed up. This

is the crux of the problem.

My last posting was not with the intent to " teach " ; it was to apply

scientific analytical skills to the thoughts being posted. If you want

teaching there are university classes; a forum is not the place to learn

basic knowledge but to expand and analyze knowledge and theories.

A discussion means that people address the same point, analyze thoughts,

discuss the pros and cons, the merits and faults of studies, and so on. At

least this is what should take place

Anyone educated in the mechanics of running would know that technique is

very important and that there are more forces involved in creating running

speed than mere ground reaction forces. But the proponents of GRF say that

it is the one and only force that is responsible for everything that occurs

in running. Do you too believe that you don't have to explain how this can

be or to prove how it is related to all other aspects of running?

This should not be a contest. Good research should answer questions and

even raise questions for future study. Each study should stand on its own

two feet and should be substantiated and explained and be able to withstand

all forms of criticism. This has not been done by the proponents of

Weyend's conclusions.

If you thought I was addressing a class you are sadly mistaken. If you

think that I consider that the readers on this forum are my students you are

doubly mistaken. But if I expect others to explain their knowledge when

they make statements that are supposed to be true then yes, I strongly

believe in this and it guides my statements.

The whole point of my posts was not to push my views; it was to see if the

comments being made were valid. This is the issue -- why don't you tackle

this instead of my attempt to help the reader know how to identify poor

research and incorrect conclusions? I can help you out with the physics

and mechanics of running if desired.

It is not my intent to enlighten members on the mechanics of running. To

do this is too complex in a simple post. This is why if anyone is truly

interested in the mechanics of running I recommend that they read the two

studies that I quoted and my book, Explosive Running. It is the only book

that goes into a detailed analysis and description backed up by pictures

taken from live digital film. With this background I would then be happy to

discuss any aspect of running mechanics. I explain every statement I make

and back it up with sound substantiated information. Anyone is welcome to

criticize any of my statements and I will gladly respond.

I never tried to promote a new position or " my position " . If you read

carefully the posts that I have written they have only been in relation to

what others have said. They are the ones taking a position that cannot be

substantiated. This is the crux of the problem. But you ignore this.

A forum is not the place to learn the basics of physics and the rudiments

of running etc. A forum is a place to discuss ideas and practices, not a

primary teaching forum. My intent is to discuss and analyze ideas and

studies and other points in the physical education realm.

But since it appears that this is not an objective of the Supertraining

forum, I will no longer participate.

Yessis, PhD

Professor Emeritus, CSUF

President, Sports Training Inc.

www.DrYessis.com <http://www.dryessis.com/>

CA, USA

March 9, 2009

Dr Yessis,

>>Instead of criticizing me and my " ideas " - which I have not posted >>-- why

I don't critic you or your ideas. Not at all. In fact this post of mine had

nothing to do with science whatsoever.

I merely observed that many of your posts are not so welcomed by many ppl as

they should be. From different reasons, they where mislabeled by ppl (you can

see this as even some of your last post was misinterpreted and some considered

them " rude " ), so I just made an observation as what I consider to be the cause.

My post was a blank statement of what I have observed on the list and of what I

consider to be the cause of some ppl being very " resistant " to your posts

I apologize if i offended you indirectly.

Dan Partelly

Oradea, Romania

March 9, 2009

Dr Yessis stated: " What I've been trying to have Ken explain is how the

forces are produced - which includes the joint actions that occur - and

how they generate horizontal speed. This has not been answered. If you

think you know the answer please share it with the group. "

The answer to his question, how horizontal speed is generated, was

addressed several times during the discussion. Apparently, as often

happens in discussions, the answers were either missed or deemed

unacceptable.

Briefly, horizontal speed is initiated at the beginning of the run. At

the first step out of the blocks (or just from the running surface),

horizontal force is approximately 60% of vertical force (depending on

the amount of vertical force, horizontal force would equal 60% of that

amount). By step 3, horizontal is about 40% and shortly thereafter,

drops to approximately 10%.

Here's some additional information from more recent research than that

offered by Dr. Yessis (italics and underlining is mine): " The

independent effects of gravity and inertia on running mechanics " Chang,

Huang, Hamerski and Kram. JEB 2000

" Surprisingly, gravity also affected the horizontal impulses generated

against the ground to brake and accelerate the runner with each step.

With a 30 % increase in gravitational and inertial force (+GF+IF), there

was a 28 % increase in the horizontal impulses generated against the

ground. In contrast, with a 30 % increase in inertial force (+IF) alone,

there was only an approximately 10 % increase in horizontal impulses.

By deduction, our data indicate that the difference in the horizontal

impulses between the two treatments (approximately 18 %) is due solely

to gravity. Furthermore, with a 75 % reduction in only gravitational

force (-GF), there was a 53 % decrease in horizontal impulse. A related

phenomenon was actually seen by W. O. Fenn as early as 1930.

Fenn (1930) observed a coupling between vertical and horizontal forces

with changes in forward running speed. Contrary to our original

hypothesis and intuition, these data indicate that gravity affects not

only the generation of active vertical forces but also indirectly

affects the generation of horizontal forces. Gravity (rather than

inertia) appears to exert the major influence over both vertical and

horizontal force generation during running. "

From the same study: " As the instant of toe-off approaches, the

horizontal ground reaction force again returns to zero. It is important

to note that, for a person running at a steady speed, the

time-integrated braking force, or impulse, must equal the propulsive

impulse.

Dr Yessis suggests the backward and downward drive of the leg propels

the runner horizontally through muscular force by the runner's volition.

From his discription, no braking action could or would occur at any

point of the run, including steady speed. Obviously this is contrary to

the research not only conducted by the authors of the above but by

dozens of experts in the field of locomotion.

Additionally, Dr Yessis stated that push-off occurred somewhere near

toe-off. If that where the case, than force plate analysis should

clearly show a large force application just prior to toe off. In fact,

that is not the case. Force plates show maximum application just prior

to half-way through the stances phase, then rapidly fall off to nearly

zero just prior to toe off.

The researcher followed with:

Our results contradicted our intuitive reasoning for the role of

horizontal forces generated by running animals. If horizontal forces are

not generated in proportion to overall mass, then why is there such a

universal pattern of braking and accelerating characteristic of all

running animals?Although it is sometimes easier to consider force data

as independent components in a Cartesian coordinate system, there is no

justification for expecting biological systems inherently to operate in

such a system. Analyzing the resultant force vector, rather than its

components, may explain why gravity (rather than inertia) has such a

great effect on horizontal forces.

The horizontal forces are modulated so that they change in proportion to

the vertical force. Proportional changes in both vertical and horizontal

forces allow the alignment of the resultant force vector with the leg to

be maintained across a wide variety of running conditions. We suggest

that the alignment of the resultant force vector with the leg during

times of high force generation may be a universal mechanism for

minimizing net muscle moments, muscle forces and metabolic costs during

running.

In conclusion, in human running, gravity, and not inertia, exerts the

major influence on both vertical and horizontal forces generated against

the ground. "

Ken Jakalski made the above clear in his posts to Dr. Yessis. Vertical

force is the dominant factor that must be understood rather than

horizontal force. In addition, this changes the focus of training away

from either a sole or major reliance on the horizontal direction of

running.

In contrast to his post below, Dr. Yessis has constantly referred to

information that can only be found in his book or in other resources

that are difficult or impossible to find.

Personally, I cannot understand why it is necessary to rely exclusively

on information that is more than 30 years old, especially if that

information regards speed enhancements via horizontally based drills and

exercises. If vertical force is dominant, then training should have its

primary focus on the vertical.

Barry Ross

Los Angeles, USA

>

> The whole point of my posts was not to push my views; it was to see

if the

> comments being made were valid. This is the issue -- why don't you

tackle

> this instead of my attempt to help the reader know how to identify

poor

> research and incorrect conclusions? I can help you out with the

physics

> and mechanics of running if desired.

>

> It is not my intent to enlighten members on the mechanics of running.

To

> do this is too complex in a simple post. This is why if anyone is

truly

> interested in the mechanics of running I recommend that they read the

two

> studies that I quoted and my book, Explosive Running. It is the only

book

> that goes into a detailed analysis and description backed up by

pictures

> taken from live digital film. With this background I would then be

happy to

> discuss any aspect of running mechanics. I explain every statement I

make

> and back it up with sound substantiated information. Anyone is

welcome to

> criticize any of my statements and I will gladly respond.

>

> I never tried to promote a new position or " my position " . If you read

> carefully the posts that I have written they have only been in

relation to

> what others have said. They are the ones taking a position that

cannot be

> substantiated. This is the crux of the problem. But you ignore this.

>

> A forum is not the place to learn the basics of physics and the

rudiments

> of running etc. A forum is a place to discuss ideas and practices,

not a

> primary teaching forum. My intent is to discuss and analyze ideas and

> studies and other points in the physical education realm.

>

> But since it appears that this is not an objective of the

Supertraining

> forum, I will no longer participate.

>

> Yessis, PhD

> Professor Emeritus, CSUF

> President, Sports Training Inc.

> www.DrYessis.com <http://www.dryessis.com/>

>

> CA, USA

>

March 10, 2009

People,

The knowledge that Dr. Yessis can offer is to valuable for this group to

go on without him. I would like to help him (and you as well) in trying

to bridge the gap that lies between you.

Personally, I was always taught that gravity is a force that works

straight down. So reaction to this force must be up, straight up,

completely straight up. I my opinion (in my knowledge of the science),

there is no forward component to this force vector. Am I that wrong?

I can understand though that the running body (I have no coaching

experience with runners) can use (or transform if you like) this force.

I think that's what your are all saying very loud. What I would like to

point out is that I can not believe that this is just something that

goes " automatic " . I want to know what actions the running body has to

undertake to make use of gravity (= a force straight down) and give the

reaction force to this vector a forward component. (cfr. with a 30 %

increase in gravitational and inertial force (+GF+IF), there was a 28 %

increase in the horizontal impulses generated against the ground).

Force is, and stays (to my knowledge) a vectorial unity. Is that

something you say in English? This means that a force can be divided

into a forward and a downward component, and that the downward component

of a force can add in no way to make the forward component greater! But

obviously, while running, the body can do something and make good use of

the force of gravity. That is something I can believe. The question I

ask is simply: HOW.

I hope I'm helping, and not adding to the confusion.

Marc De Ron

Antwerpen (Belgium)

Jon Haddan had in de originele mail geschreven op 9/03/2009 21:37:

>

> Dan,

>

> Why do you think Dr. Yessis' posts should be more welcomed than they

> are? You may not have been on the list the last time we went through

> this, but Ken and Barry answer questions, set forth positions and

> quote from reputable sources. Others contribute their thoughts or

> ideas. Dr. Yessis dismisses everything said, provides no answers of

> his own, and, in the end, and rather predictably, pitches his own

> books claiming the topic is just too complex for a discussion board.

>

> Jon Haddan

> Irvine, CA

>

> From: Dan Partelly <dan_partelly@...

> <mailto:dan_partelly%40yahoo.com>>

> Subject: Re: Mechanics of speed

> To: Supertraining <mailto:Supertraining%40yahoogroups.com>

> Date: Monday, March 9, 2009, 9:58 AM

>

> Dr Yessis,

>

> >>Instead of criticizing me and my " ideas " - which I have not posted

> >>-- why

>

> I don't critic you or your ideas. Not at all. In fact this post of

> mine had nothing to do with science whatsoever.

>

> I merely observed that many of your posts are not so welcomed by many

> ppl as they should be. From different reasons, they where mislabeled

> by ppl (you can see this as even some of your last post was

> misinterpreted and some considered them " rude " ), so I just made an

> observation as what I consider to be the cause. My post was a blank

> statement of what I have observed on the list and of what I consider

> to be the cause of some ppl being very " resistant " to your posts

>

> I apologize if i offended you indirectly.

>

> Dan Partelly

>

> Oradea, Romania

>

March 10, 2009

I'm trying to follow the discussion on mechanics of speed (but am not interested

who has the better insight, theory and who is teaching who).

There's an ancient article I remember:

- " Zum techniktraining beim Laufen " (German; free translation " technical

training during running " ) by Jakob Waser in 'Leistungssport' 1984.

In the article the 2 'schools' for running techniques are discussed.

It appears that those who know how to pull, i.e. accentuate hip extension, run

faster than those who almost only try to push, i.e. accentuate knee and ankle

extension.

As an example he compares a regional female runner (6,3 m/s, flight height 3,6

cm) and a male sprinter (11,5 m/s, flight height 2,6 cm).

In order to try to prove the technical superiority of pulling technique, the

researcher started a technical training with the girl, focussing on more

pulling. The girl (16 years old at the start of the research) improved from 66

to 59 seconds within 12 months. The writer points out that other physical

improvements may also have lead to this kind of improvement, but the technical

changes showed a lower vertical GRF and a higher horizontal GRF.

Florence Griffith was one of the extreme pull-technique runners. There was a lot

of discussion on her body position, that seemed to lean backward.

If you look at the biomechanics, pulling backward is a logical part of the

movement cycle. If the leg would follow the 'normal' cycle, after the knee

upward movement the lower leg moves forward and consequently the hamstrings are

lengthened, thereby extending the hips. The foot will then have a backward

velocity towards the body and - if you do not want to accellerate - will ideally

have no velocity towards the ground (or only the backward velocity that is

needed to overcome the braking influence of wind/air). At almost any point of

the cycle the (mostly) bi-articular muscle group will be lengthened in one joint

and shorten in the other.

I used a force plate at different running velocities 8 and 14 km/h and found the

following changes:

- almost equal flight times (slightly higher flight times during 14 km/h)

- much lower contact times at 14 km/h

- higher GRF during 14 km/h

- steeper rise at start contact and fall at end contact of GRF at 14 km/h.

Considering that the flight time is almost the same and thus the 'flight height'

was about equal, the change in contact time is the cause of the higher GRF, i.e.

a higher stiffness.

It should be noted that the GRF was still high just before take off, see also

attached picture (1 step).

At the accelleration phase, especially the first 20 m, the pushing technique

will be advanteous over pulling, as the body mass is in front of the contact

foot. From that moment pulling and a short contact time may deliver higher

maximum velocity, yet it is to the anatomy and physical development of the

individual what technique will bring him/her the best times.

Cheers,

Huizing

The Netherlands

March 10, 2009

> Personally, I was always taught that gravity is a force that works

> straight down. So reaction to this force must be up, straight up,

> completely straight up. I my opinion (in my knowledge of the science),

> there is no forward component to this force vector. Am I that wrong?

No, you are quite right. To achieve any forward movement a body must

be able to exert some force with a horizontal vector. This is usually

achieved thru' use of friction with the ground surface. Amonton's

first law of friction says the friction is directly proportional to

the load, i.e. the vertical vector pointing down from the force of

gravity. The heavier vehicle/runner can exert more horizontal force

without slippage given the same area of contact.

Also important is the coefficient of friction, which depends on the

materials of the track, road, field, shoes, tires, etc. With a low

coef. like with steel wheels of a train and steel tracks, wetted by

rain, the wheels just spin unless the horizontal force is added

slowly. Same with a runner trying to run on ice wearing flat leather

soled shoes.

Fair winds and happy bytes,

Dave Flory,

Flower Mound, TX, U.S.A.

March 10, 2009

Hi Marc,

I don't believe that anyone is trying to push Dr. Yessis off of this

thread.

What many of us are concerned about is that we've offered a significant

amount of research to back our position on the issues presented. Much

of the research is from 1992 through at least 2006 and is presented by

some of the renowned experts in the field. Many of the experts we've

cited are relatively new and some have been publishing since the

1960's.

Dr. Yessis has not responded in kind. He presents his own book on

running but has neither addressed the viewpoints of current resources

mentioned in several posts nor offered any research based information of

his own, or that of others.

If you look through some of the earlier posts you will see where we've

addressed the issues that Dr. Yessis claims we have not.

While the gravitational forces are a very necessary component of faster

running, so is Newton's law- that a body in motion tends to stay in

motion.

Researchers in this field often use the analogy of a bouncing ball to

that of running. No one instructs the ball how to bounce, yet when we

throw it along a road it uses gravity and its elastic components to move

in a horizontal direction. It does not paw-back to move forward in the

horizontal direction.

Many of the better well known researchers in the field of locomotion use

a similar analogy. Cavagna's " Elastic bounce of the body " JAP 1970 is

one of the early works.

What has been left out of much of the discussion is time. An elite

runner will have ground contact time of approximately 0.08 s.

Force plate measurements show that nearly all of the force applied to

the ground as support force occurs prior the end of the first half of

the stance phase. It is doubtful that any of us could willfully produce

multiples of body weight as support force in that amount of time

(delivery is primarily isometric contraction).

If we assume that the runner is able to deliver this much force at or

near toe-off (as Dr. Yessis contends) we should certainly see the

evidence of this force application on the force plate. Again, what we

see from force plates analysis is peak force prior to the half way

point of the stance followed by a rapid drop off to nearly zero prior to

toe off.

Dr. Yessis has challenged the concept of running being driven, so to

speak, by vertical, mass-specific force. Instead, he offers force

application occurs where force plate analysis does not show this to be

the case, and that force delivery of multiples of body weight is

attainable by volitional muscular contraction in a few hundreths of a

second--repeated multiple times over the course of multiple foot falls.

Certainly this issue could end immediately upon Dr. Yessis posting

relevant information by the current crop of locomotion experts!

Barry Ross

Los Angeles, USA

> > From: Dan Partelly dan_partelly@...

> > <mailto:dan_partelly%40yahoo.com>>

> > Subject: Re: Mechanics of speed

> > To: Supertraining

<mailto:Supertraining%40yahoogroups.com>

> > Date: Monday, March 9, 2009, 9:58 AM

> >

> > Dr Yessis,

> >

> > >>Instead of criticizing me and my " ideas " - which I have not posted

> > >>-- why

> >

> > I don't critic you or your ideas. Not at all. In fact this post of

> > mine had nothing to do with science whatsoever.

> >

> > I merely observed that many of your posts are not so welcomed by

many

> > ppl as they should be. From different reasons, they where mislabeled

> > by ppl (you can see this as even some of your last post was

> > misinterpreted and some considered them " rude " ), so I just made an

> > observation as what I consider to be the cause. My post was a blank

> > statement of what I have observed on the list and of what I consider

> > to be the cause of some ppl being very " resistant " to your posts

> >

> > I apologize if i offended you indirectly.

> >

> > Dan Partelly

> >

> > Oradea, Romania

> >

March 10, 2009

The last three posts bring out very clearly some of the points have tried

making. Rather than trying to answer or rebut the comments,, just most of

which are erroneous, I believe we need a third party who has not taken

sides. To this end I ask the moderator, to step in to clarify a

few points..

Where in any of my posts did I say I did not believe in the spring-mass

model? I never said this because I do believe in it. What I did question

was how it applies in running in generating the horizontal force. How how

is the vertically directed loading (spring compression) returned to propel

the body forward? where was this explained? Keep in mind that the body

does not have to act as a spring.

It has been brought out that the forces on landing are greatest in the first

part of the landing. There is no disagreement here. Where did I ever say

it was not ? My question was how the GRF ( and/or the support force which

we were told were two concurrent forces) was converted to horizontal force.

Was this ever answered?

I'm sure the answers to these two questions can be done in one or two

paragraphs without bringing in any other related material.

As I previously mentioned, one can have a good discussion if it stays on

point and if there aren't erroneous conclusions being made. Some people

kept asking where are my views. This is immaterial at this stage unless you

want to have a contest to see who has the best sounding comments and then

you make a decision on which one you like. Questions were asked specific to

points that were mentioned. This is the only argument that we should see.

Yessis, PhD

Professor Emeritus, CSUF

President, Sports Training Inc.

www.DrYessis.com <http://www.dryessis.com/>

CA, USA

March 11, 2009

I am fascinated by this topic, I am nowhere near the expert you all are, but

nonetheless I am learning, but it amazes me how an opinion is asked, someone

answers then gets berated or mistaken in what they said. I hope this stays as

an educational forum and not a place where someone has to satisfy their

ego...everyone here has great ideas, let's share them and take from what is said

and use it as you wish but please stay professional.

Bill hawkins

Certified youth training specialist

Cleveland Ohio

===========================

Subject: Re: Mechanics of speed

To: Supertraining

Date: Tuesday, March 10, 2009, 9:01 PM

The last three posts bring out very clearly some of the points have tried

making. Rather than trying to answer or rebut the comments,, just most of

which are erroneous, I believe we need a third party who has not taken

sides. To this end I ask the moderator, to step in to clarify a

few points..

Where in any of my posts did I say I did not believe in the spring-mass

model? I never said this because I do believe in it. What I did question

was how it applies in running in generating the horizontal force. How how

is the vertically directed loading (spring compression) returned to propel

the body forward? where was this explained? Keep in mind that the body

does not have to act as a spring.

It has been brought out that the forces on landing are greatest in the first

part of the landing. There is no disagreement here. Where did I ever say

it was not ? My question was how the GRF ( and/or the support force which

we were told were two concurrent forces) was converted to horizontal force.

Was this ever answered?

I'm sure the answers to these two questions can be done in one or two

paragraphs without bringing in any other related material.

As I previously mentioned, one can have a good discussion if it stays on

point and if there aren't erroneous conclusions being made. Some people

kept asking where are my views. This is immaterial at this stage unless you

want to have a contest to see who has the best sounding comments and then

you make a decision on which one you like. Questions were asked specific to

points that were mentioned. This is the only argument that we should see.

=============================

March 13, 2009

Dr. Yessis,

Thank you for addressing the questions asked.Â I think it would have been a lot

more productive if in the beginning you had laid out your positions relative to

the Weyand study than the way this thread unfolded.

Since you stand by your statement about pushoff, notwithstanding Kenâ€™s

references to studies showing little force at pushoff perhaps the two of you are

using different definitions of push off.Â Are you defining the first third of

the stance as part of pushoff?

I didnâ€™t state any interpretations about the driving of the leg forward.Â I

just quoted your book and asked you to reconcile the quote " the greater the

force in driving the leg forward, the faster the thigh comes forward and the

faster your potential speed " with the fundamental conclusion of the Weyand study

that the speed of the leg limb in air (part of this would be the drive forward)

wasnâ€™t the basis for speed.Â The two seem to me to be at odds.

Based on your statement, " The greater the speed with which the leg is brought

down and back, the greater the force generated on touchdown, " faster legs should

produce greater force, but Weyand says runners with similar swing rates can

produce significantly different forces.Â Kenâ€™s other references also state

that increasing the rate of speed of the foot can cause collision forces that

reduce speed and still other references that show the foot actually slows down

before impact.

I realize that your book was not written for the academic community.Â That is

why when we are dealing with various scientific studies references to your book

alone do not suffice.

There are obviously significant differences between how you see running and how

Weyand does.Â Weyand, however, is not a maverick in the field of locomotion.

His positions appear to be shared by most everyone else in his field.Â I have

not seen any published papers questioning his findings.Â There are simply more

and more papers on different aspects of running (like examining the forces at

work in running the curve) that describe running the same way he has.

At the time your book was published your positions were shared by a large number

of coaches. Â I have no doubt that there will be support for your positions in

the Soviet Sports Review.Â The problem is that at the time your book was

written, Loren Seagrave was producing Speed Dynamics, and the papers in the

Sports Review were being written, the locomotion scientists were not part of the

discussion. Â Now that they are and are studying issues directly related to

human sprinting we have a conflict.Â I believe that what the locomotion experts

might say to try and reconcile the differences is that the studies in the past

observed movements and sometimes measured muscle activity, but did not record

and study forces.Â Those studies could not necessarily differentiate cause from

effect and, in fact, often described effect as cause.

I believe Weyand does address stride length.Â He states, " At any speed,

applying greater forces in opposition to gravity would increase a runnerâ€™s

vertical velocity on takeoff, thereby increasing both the aerial time and

forward distance traveled between steps. "

Obviously, you believe WeyandÂ to be wrong and you canâ€™t both be right.Â Â Â

I just donâ€™t know of any current studies that confirm the statements in your

book while taking into account the findings of studies like Weyandâ€™s.Â With

the locomotion experts in general agreement about running, there does not seem

to be enough current support for your position to favor it over Weyand's.Â

The 2000 Weyand study does not address technique as far as I can recall.Â It is

true though that the locomotion experts do not see technique the way certain

track coaches do.Â They see running as a much more natural activity than

coaches.Â Ken has previously referenced studies that show that efforts to get

runners to meet some idealized form increase the energy cost of running and are

seen as counterproductive.

That doesnâ€™t mean that there is no need for technique work in track.Â

Obviously there are some people who need some corrections.Â A runner who bolts

upright at the firing of the gun, shuffles their feet or has a very unusual arm

swing could benefit from technique work.Â

I am certain that Ken spent as much time as the next coach on technique work at

one point in his career.Â Now that he has become a minimalist, I doubt that the

technique of his current crop of runners looks much different than those in the

past.Â

Jon Haddan

Irvine, CA

Â

Subject: Re: Mechanics of speed

To: Supertraining

Date: Thursday, March 12, 2009, 4:58 PM

Jon

Yes I refused to put forth my position because it was immaterial. I merely

asked for an explanation of the statements that were made.

Since you now have specific questions from my book Explosive Running I will

be more than happy to answer.

In regard to the pushoff, I stand by my statements. As I replied to Ken,

you must look at when ankle joint extension is taking place. It is not a

moment - it takes place as the body moves further in front of the pushoff

point to get the CG as far out in front as possible. At the moment of toe

off the foot is only superficially in contact with the ground. Thus there

are no measurable forces at this time. This is why it is important to look

at what is happening to the runner when forces are being generated.

Although never brought out by Weyand or anyone else in this discussion,

ankle joint extension is how the forces generated during touchdown are

released. The knee joint remains slightly bent during pushoff so that it

cannot be the way the energy is returned. I know you believe that my

question was answered in regard to how the energy was returned but I am

still waiting for an explanation from the proponents of the Weyand study.

In regard to " the greater force in driving the leg forward,... I never said

that the driving of the leg forward was the primary cause of speed. This is

your interpretation. As I state further on there are three key actions.

The forward thigh drive is only one of them. It is impossible to reconcile

this with the Weyand study because they only looked at one aspect of the

total run. They try to explain everything that occurs in running based on

force at contact. They did not take a look at why the runner does all of

the actions that he does. If they did, they would not have overreached as

much as they did.

In regard to the leg being brought back forcefully to make contact with the

ground, this is not so much a contradiction as it is understanding the role

of different forces. The leg is brought back forcefully to minimize or even

nullify braking forces. If the leg was not brought back forcefully to equal

the speed of a forward moving body there would be horizontal braking forces.

To say that there is zero force in this case would be great. And if the

leg were not brought back very quickly and forcefully touchdown would occur

well in front of the body. Braking forces would be quite evident at this

time.

Understanding what takes place in the running stride is very important. The

Weyand study ignores everything that the athlete does in running and tries

to explain total running from the force generated on touchdown. For

example, I have not seen anything about stride length. I think everyone

agrees with the finding that the speed of force generation and amount of

force generated during touchdown is the key to stride frequency. How does

it explain stride length? For this you have to look at more than just

contact force.

If I were writing a book for the academic community I may have given many

references. My book was written for practitioners and runners who are

interested in learning more about what takes place in the running stride.

Most runners as a group are not interested in reading or wading through

research studies. However if you are interested in more studies I direct

you to the Soviet Sports Review, later known as the Fitness and Sports

Review International. In fact, of the thousands of books that are out there

I have never received a single comment (except in this group) complaining

about the lack of references.

As the old saying goes, " a picture is worth a thousand words " . Thus it is a

shame that Weyand did not look at running technique and try to explain the

actions that the runner does based on his solitary finding. To conclude

that technique is not important sets back the thinking in track many years.

Yessis, PhD

Professor Emeritus, CSUF

President, Sports Training Inc.

www.DrYessis. com <http://www.dryessis .com/>

CA, USA

March 14, 2009

We'vementioned several times that Dr. Yessis is asking much of the same

questionsnow that were previously answered.

Here ispart of the '06 exchange:

<Yessis: If he [Weyand] and his associates had a strong understanding

of running how did they arrive at the collusion that this topic was

worthy of research? Did he show the need for this study? Is there a

conflict in the literature as to the role of the legs and what produces

the force in push-off?>

Ken: The reason for the study was to put forth a mechanical explanation

for the limit to running speed " with a more concrete physiological

basis than the consideration of maximal stride lengths and frequencies

that have typically framed this question. "

<Yessis: Since this study revolves around leg repositioning why was no

role given to this i.e., what role do the legs play? We are told that

leg action is not important nor is technique. If true, why do we even

have to reposition the legs?

Why not just let them hang and relax and land wherever?>

Ken:The point of the study was that, although top sprinters have faster

muscle fibers and greater muscular power available to reposition their

limbs, they do so little or no faster than average and slow human

runners do.

Activation of the flexor muscles and tendons that reposition the limb

during the swing period is considerable at high speeds, but this

activation " likely occurs to increase the storage and release of

mechanical energy in the oscillating limb rather than to generate

mechanical power chemically within these muscles. "

<Yessis:That the limbs are repositioned via the release of elastic

energy is well established. What was not addressed in the study was what

role they play in running. Don't the legs create a forward force when

driven forward with great acceleration? Why was this ignored?>

Ken: When legs are driven forward with great acceleration, this is the

acceleration phase of the sprint.This was not ignored. This study

focused on the mechanics at top speed.

<Yessis:Does this action not contribute to forward speed? If you do this

in a standing position you will fall forward; isn't this a force? If the

limbs do not contribute, why do we swing our arms and legs up or forward

in jumping? Spring -mass studies show the importance of these actions.?

Ken: This is an entirely different situation mechanically. Yes, I agree

with what is stated above.Jumpers, unlike sprint runners do need to

develop power to jump. The requirement for runners is force rather than

power, that is, once they have accelerated to race velocity. Power is

important for acceleration. I also believe that the swing limb action of

a jumper is quite important to the jump.What you are doing is confusing

a transfer of momentum with the spring mass model.

<Yessis:Great importance is given to ground reaction forces. From what

can be found in the discussion the ground reaction forces were measured

at touchdown where vertical forces were greater than horizontal.This is

understandable.

But how can vertical forces propel the body forward?>

Ken: The body is moving forward over the grounded foot This is why we

have asked you to tell us the speed of the center of mass over the

grounded foot.

As I may have mentioned previously, there are two ways to consider the

limb's motion before touchdown:1) it's velocity with respect to the

track and 2) its velocity with respect to the body or center of mass. In

the second case the limb decelerates to a stop and retracts back toward

the body and the ground, but because the body is traveling forward so

quickly, the velocity of the limb with respect to the track is still

positive.

<Yessis:Why are there no ground forces at the the moment of takeoff?

How can this be especially in view of EMG studies done showing the role

of the Achilles tendon and calf muscles in returning energy for the

push off.

Most studies done on return of energy use ankle joint extension

which(according to the conclusions) is unimportant and plays no role in

running. As any good researcher will tell you it is necessary to explain

the results. If this is not possible more studies are called for.>

Ken:It´s been over six years since this study, and the number of

times the study has been cited in many other peer reviewed journals,

other experts such as Komi and Mann confirming the swing data, the fact

that no study has been undertaken challenging either the swing or

support force findings, and since the peer reviewers found no concerns

with the methodology, data, or implications, all this seems to indicate

that there is no need to `explain´ the results.

The " Results " section of the paper is five pages long If

you still don´t get it, I should offer that Barry's advice makes

sense: talk to the researchers, visit their labs, and review their

procedures.

<Yessis:Thus if ground reaction forces are the key to faster running

speeds we should be told how these forces are created and used. The role

of gravity in this case is overestimated. Were calculations done to

measure the force produced by gravity?>

Ken: Questioning this means you are unclear as to what is meant by

average mass specific force. It is force applied to oppose gravity

during the period of foot-ground contact.

<Yessis:If they were how could they conclude that gravity is the main

force to contend with? This does not require rocket science. Simply

calculate the force produced by a free falling body over a distance of

1-2 inches and you will be unable to produce up to 5 times body weight

force.>

Ken: Yet that is exactly what is happening, and this is vertical force.

All of this has been presented to you in the graphs of vertical and

horizontal force. Any time a muscle generates force, the tendon must be

loaded to transmit the force to the bone - otherwise, no movement

occurs. The central point is that the net work performed is zero -what

little is performed is achieved largely passively so that what the

muscles are doing mechanically is lots and lots and lots of force

generation and very little shortening work

<Yessis:Thus how is up to 5 times body weight force created? Does it

exist in the isometric contraction of the leg muscles as was

postulated?>

Ken: If you had answered Barry´s initial question, you would see

that it is not related to muscle shortening. No athlete could overcome

five times body weight on one leg through active muscle shortening At

the hip, as knee and ankle - ground support forces are generated

entirely by the extensors muscles.

The force on the ground is set by body weight - it has to equal the

body's weight over the course of the stride. The force trace looks a lot

like an inverted U. Thus, the forces at touchdown and toe-off are very

small and the most of the force action occurs in the middle of the

stance phase.

In simple terms, the body loads the limb, not the other way around. Fast

moving limbs via pawing or clawing have no effect on the net requirement

for force or the force that is ultimately generated.

<Yessis:But how can this be when no to very little movement in the leg

joints takesplace during the latter half of the contact phase?>

Ken: All force tracings show forces peaking at mid-stance. We have

explained this more than once already.

<Yessis:If the vertical forces are so important in forward propulsion as

we are led to believe in the spring-mass model, why does the leg remain

bent in the knee at takeoff? This indicates a less than total return of

energy from a relatively small amount of ground force created by

gravity>.

Ken: First of all, you are using the term forward propulsion relative to

top speed. It is a matter of absolute fact, and the most basic

mechanics, that on a net basis runners traveling at a steady speed exert

no net propulsive force on the ground. Regarding the issue of total

return of energy, you are looking at the final third of stance phase,

which again resembles an inverted U. All force plate studies will reveal

this

<Yessis: Is this how the spring model is used to describe running? Does

it take into consideration horizontal forces? If yes where is the data?

If the spring-mass experts use only vertical force data (which they must

to describe spring action) how do they reconcile this apparent

discrepancy?>

Ken: Because the net horizontal forces exerted by the test subjects

during each stride could not explain the differences in the top speeds

they attained, they were not included in the analysis.

<Yessis: I can go on but I hope this is sufficient to show that the

study and its conclusions did little if anything to clarify and explain

what takes place in running.

But if you and others still believe in the apparent incorrect

conclusions I will leave you with the conclusion of the spring model

experts who describe running as " a ball bouncing down the track " . To put

this conclusion into practice have your runners practice bouncing as

they " run " . To create more force have them bounce higher and higher to

create more ground force and its resultant speed.>

Ken: What the super ball and skipping stone have in common with the

runner who is up to speed is that each conserves its forward

speed/momentum by bouncing. No net input of propulsive force required

-bodies in motion tend to stay in motion. Unlike the super ball, which

bounces passively, runners must turn n their muscles to allow their legs

to function as springs. If they cannot apply force sufficiently rapidly,

the springs don't work and they do not maintain speed.There is no need

to practice `bouncing. "

<Yessis: if you prefer to think of running as " a spring bouncing down

the track " , have the runners practice with pogo sticks to get a better

feel for the spring action on each step. To cover more distance have

them strive for more height on each jump.>

Ken: It is interesting that you should mention this, even in a facetious

manner. In a sense, the pogo stick is at the heart of spring mass

research, and you probably weren´t aware of that.

The bouncing and the spring analogies began with a kangaroo study at

Harvard´s Concord Field Station in the early 70s. Kangaroos

bounce more obviously than runners - they also break the rules of

energetics and speed. The kangaroos and the wallabies do not increase

their metabolic rates when they go faster - it a flat line for VO2

vs.speed.

After the legendaryDick bounced the kangaroos on the lab´s

treadmill, he then recruited thebest pogo sticker at Harvard to do his

thing on the treadmill. Later herealized the mechanics he wanted didn't

require the stick; he could simply havepeople hop on two feet.

Dick and TomMcMahon put in a considerable amount of time trying

to quantify elastic energystorage without succeeding, but McMahon did

succeed in generating accuratepredictions about the mechanics of running

by treating the system as a simplespring mass system. Basically,

it´s a one-legged animal with all the masslumped at the hip. Many

tests later, the model has held up incredibly well.Runners behave just

like springs under steady state conditions. And what doesthis mean?

Essentially, the relationship between the force on the ground andthe

displacement of the CM is the same during the yield and rebound phases

ofthe contact period. Springs by definition have the same relationship

betweenforce and displacement on compression and release or stretch and

release - andthis is how the body behaves during running.

If you feel that " legsprings " are at best entertaining,

then I suggest you also take a look at the work of Dr.Rob Playter, whose

research has demonstrated that a person doing what seems to be a highly

skilled maneuver is only taking advantage, at a very basic level, of

forces acting on him or her. His research team has found that computers

controlling robots don´t need to tell each joint how to move at

every instant; they only need to adjust the length of the stride and the

springiness of the leg.

<Yessis: I apologize for being facetious but isn't this a logical

conclusion to draw from the experts?>

Ken: Dr. Yessis. I believe we have been more than straightforward in

attempting to answer your questions.If you go to Barry´s site,

you will see graphs, images, data, and corroborative findings from other

studies. We provide detail, after which you continue to claim that we

are simply clouding the issues. You will accuse us of evading questions,

yet the reality is that some of your questions indicate to us that your

area if expertise may not be locomotion research or that you are

unaccustomed to interpreting force data. You offer no studies of your

own, you allude to archival Russian research which you have not

produced, and you propose as the best source for truly understanding

running mechanics your own book, which has no data and references

whatsoever. Can´t we just end this?

All I ask is that you refrain from consistently bringing

up-especially in completely unrelated posts-the

shortcomings of a study you quite sincerely believe is flawed yet we

quite simply believe you do not understand.

----------------

In this new iteration of the same topic, Dr. Yessis stated: " In regard

to push-off, I stand by my statements. As I replied to Ken, you must

look at when ankle joint extension is taking place. It is not a moment -

it takes place as the body moves further in front of the pushoff point

to get the CG as far out in front as possible. At the moment of toe off

the foot is only superficially in contact with the ground. Thus there

are no measurable forces at this time. This is why it is important to

look at what is happening to the runner when forces are being

generated. "

It is unclear what Dr.Yessis means by " superficial " contact.

Regardless, Dr. Yessis now claims that the body must move further in

front of the pushoff point to get the CG as far out as possible.This can

only mean that active, forceful push off must occur sometime after

mid-stance but prior to the time that the grounded foot has only

superficial(?) contact.

However, significant force application to the ground peaks prior to that

point. In fact, it peaks less than half way through the stance phase.In

other words, at no time after mid-stance is there enough force applied

to the ground to powerfully propel a runner down the track.

Additionally, given the fact that elite sprinters have ground contact

times of less than 1/10 of a second, it would be difficult for an

athlete to apply the necessary amount of force from a concentric

contraction in that small amount of time- then do it over and over again

forthe length of even a short sprint.

However, isometric force delivery could, and does, occur that

quickly--but only as support force.That is the force applied to the

ground to oppose the effects of gravity. This force clearly shows on

force plates during high speed running, increasing from toe-down to near

mid-stance, then disappearing.

Dr. Yessis has stated in this year's version of the debate that he now

believes in the spring-mass model. However statements made by Dr. Yessis

in 2006 include: " But if you and others still believe in the apparent

incorrect conclusions I will leave you with the conclusion of the spring

model experts who describe running as " a ball bouncing down the track "

and " If vertical forces are so important in forward propulsion as we are

led to believe in the spring-mass model, why does the leg remain bent in

the knee at takeoff? This indicates a less than total return of energy

from a relatively small amount of ground force created by gravity. "

Both of his comments in 2006 are somewhat facetious (according to Dr.

Yessis) regarding the spring-mass model and it's proponents. It's

difficult to understand why he claims that he believes in the

spring-mass model now when the model has not changed and neither have

questions or comments.

Readers should also note that Ken mentioned Komi, Mann, Weyand, Dick

and Tom McMahon in his responses. I mentioned several in mine as

well. However, Dr.Yessis has yet to cite a single research paper and

it's authors in any of the discussions.

Kinematics is the branch of mechanics concerned with motion without

reference to force or mass. For this reason, reliance on kinematics

alone will not tell the complete story of how we run fast and

faster.Pictures of runners cannot reveal how gravity, force and mass

affect a runner.

Barry Ross

Los Angeles, USA

>>

> If I were writing a book for the academic community I may have given

many

> references. My book was written for practitioners and runners who are

> interested in learning more about what takes place in the running

stride.

> Most runners as a group are not interested in reading or wading

through

> research studies. However if you are interested in more studies I

direct

> you to the Soviet Sports Review, later known as the Fitness and Sports

> Review International. In fact, of the thousands of books that are out

there

> I have never received a single comment (except in this group)

complaining

> about the lack of references.

>

> As the old saying goes, " a picture is worth a thousand words " . Thus

it is a

> shame that Weyand did not look at running technique and try to explain

the

> actions that the runner does based on his solitary finding. To

conclude

> that technique is not important sets back the thinking in track many

years.

>

> Yessis, PhD

> Professor Emeritus, CSUF

> President, Sports Training Inc.

> www.DrYessis.com <http://www.dryessis.com/>

>

> CA, USA

>

March 14, 2009

While I agree with almost all of what Dan states below, there are 2

points that should be clarified:

Dan has no idea who I coach or at what levels. I am currently working

with several athletes in different sports, some in D1 colleges and

others who have been or are currently competing at the elite level.

With one exception, I have not revealed the names of anyone I personally

coach beyond the high school level.

The title " Holy Grail " was from an article posted on Dragondoor.com and

referred to the need of sprint coaches to focus on training that would

enhance mass-specific force. My book, Underground Secrets To Faster

Running, has a similar message...focus on training M-SF

Barry Ross

Los Angeles, USA

>

> Dr. Yessis:

>

> What Dave points out doesn't apply to running at a constant speed or a

near constant speed which is what the SMM accounts for. The SMM implies

a known horizontal velocity of the COM exists and that it is constant or

near-constant. The SMM answers many problems about reduced ground

contact time and how energy is derived from the system. The vertical

forces acting on the COM must be higher with increasing velocity to

maintain stability within the spring-mass system. The horizontal forces

seem non-consequential at constant and near constant speed because they

have to be or the athlete is accelerating to an even greater velocity.

I said it before and I will say it again you painted yourself into a

corner with your questioning, avoidance of answering questions, and

relying on your own books. The difference between a runner 10 m/s and

the same runner running 10.5 m/s in snapshot analysis (focus on 1 gait

cycle) will yield only higher vertical forces as evidence greater speed

are attained with higher vertical force outputs. However, the question

becomes how do we get there? That answer is the integration of net

horizontal impulses of each of the steps in the gait cycle till near

constant velocity is reached. If we graphed the net horizontal forces

and impulses of each step and fitted a curve to them with respect to

time we should find they mirror the acceleration-time curve I have

posted on my site.

>

http://sprenten.com/blog/wordpress/wp-content/uploads/2008/12/accelerati\

on_11.jpg

>

> Once acceleration is minimized and race/running velocity is near

constant horizontal forces have to be minimized. To me its so damn

simple a concept I don't know why some greats in this field haven't

thought of testing for it before I even theorized horizontal impulse in

running and why I came up with the term mass-specific impulse. The

closest people to this line of thought are Coh and a grad student in

Australia named Richmond who published the following piece

online.

>

> http://www.elitetrack.com/articles/pdf/4042/

>

> There are items I disagree with Barry and Ken about but I am not going

to argue about the chicken and egg argument of what comes first. I will

not argue with them about how vertical forces are a limiting factor in

attaining a faster race velocity because they are a limiting factor,

where I differ with Barry and Ken is why they a limiting factor. I will

argue with them about items I think they are wrong about such as total

passivity during ground contact, how coordination happens and is learned

(motor control and learning). We are better served by saying the SMM

can explain somethings, but to account for the velocity a runner attains

it must be an adjustable spring system with power outputs that must be

derived through active means. Greater Coordination = Greater Efficiency

= Greater Vertical Forces.

>

> If you don't believe someone can do this by just deadlifting and

running fast 3x a week over very short distances then you are fooled by

your need to coach things that are unimportant. Lastly, my biggest

argument against Barry's system as well as many other systems is they

get stuck in what I term local optima. However, Barry's system is

simple and practical enough to be applied to large groups and that I

believe is its greatest benefit as his system doesn't lead to

overtraining nor does it lead to doing a bunch of nonsense calling such

nonsense form or mechanics. Do I think its the holy grail as he claims?

Absolutely not, but it may be the closest thing to the holy grail in

coaching a large group of sprinters in say a high school or junior high

setting.

>

> There is no practical way for what you would do in your books to be

applied to groups larger than say 3-5 individuals, I would even say

using your own books guidelines would make it hard to train more than 1

individual at a time. Even then I think you get away from what is

really needed to make someone better. My own methods cannot be applied

to groups larger than 15 individuals, I rely too much on feedback,

observation, and listening to athletes talk amongst themselves that 6 or

7 athletes is the optimal limit for my own methods and practices.

>

> There is no need for a third party moderator as you have called for as

most of us here have acted as a third party in this debate of which you

really only have asked questions and not provided answers to.

>

> Regards,

>

> s

> Champaign, IL

> http://sprenten.com

>

March 15, 2009

Hi ,

Thank you for posting this study!

It certainly has some interesting suggestions regarding the importance

of horizontal ground reaction force.

It would seem that two of the suggestions are very significant for

distance runners:

" This suggests that the short braking phase and use of elastic energy

are important factors both in economical

and high speed running in the group of young well-trained

endurance athletes. "

" This suggests that the horizontal component of ground reaction force is

more important in attaining high top running speed in distance runners

than the vertical component of it, since similar linear relationships

were not observed between vertical effective force and running speed,

and no significant correlation was observed between vertical force and

maximal running speed. "

However, I am curious as to why you feel it is necessary to post

research regarding distance runners when the discussion at hand is about

high speed sprinting. Could you give us the reason why you believe that

this research has merit to the current topic, especially since Dr.

Yessis has already stated earlier that he believes in the spring mass

model for sprinting?

Barry Ross

Los Angeles, USA

>

> Some articles that may be of interest in this discussion:

>

> -

http://www.kihu.jyu.fi/tuotostiedostot/julkinen/2007_num_factors_re_1000\

0.pdf

>

> - Korhonen M, Mero A, Alen M, Sipilä S, Häkkinen K, Liikavainio

T, Viitasalo J, Haverinen M, Suominen H. Biomechanical and skeletal

muscle determinants of maximum running speed with aging. Medicine and

Science in Sports and Exercise (Accepted, published in April 2009).

>

March 16, 2009

Dr. Yessis,

At this point further responses do not seem to matter.Â You say that you

believe in the spring mass model, but then you keep questioning how vertical

forces create horizontal speed. Pogo stick analogies and references to kangaroos

donâ€™t seem to do it for you.Â I think it has been explained sufficiently.Â

The fact that you do not accept any of the explanations given does not mean they

are not adequate.

Your view of what happens in the " push-off " and what others have quoted as the

forces being measured do not seem to match up.Â The statement " it stands to

reason " that the accelerating limb generates force simply does not match up to

Weyandâ€™s study that the limb speed of elite sprinters is not much different

than that of modest runners whereas the ground forces are significantly

larger.Â As I recall, almost all of the time differential in the swinging limbs

could be accounted for by the decreased contact times. Linking the thigh drive

with the push off just seems to link two flawed assumptions.

Since you think that the slowing down of the leg before impact is a function of

poor technique and not a requirement of running, can you reference a study that

shows that runners with better technique or speed do not slow down their legs

before contact. Otherwise, it is just anÂ unsupported personal opinion.Â To

paraphrase you,Â " Please don't put it again in your own words -- cite a study. "

Since you do not believe that locomotion experts are generally in agreement with

Weyand, could you offer up some studies that take issue with his conclusions.Â

We have seen one offered so far, but I have seen many more that cite him

favorably.

You stated, " Go back to my first question up above. Where is the explanation?

Please don't cite another study-- put it in your own words. " The simple response

is your inability to understand, or unwillingness to accept, the explanations

that have been given repeatedly does not make the explanations deficient.Â

There may have been a subsequent publication of your book in 2006, but the copy

know what the reference to the time following the termination of the publication

of the Soviet Sports Review has to do with anything.Â Aside from your book, it

is the only thing you reference in support of your position.Â I I assume

nothing occurred in the 12 years following the termination of its publication

that altered your views.Â However, you state that your 2006 book was " based on

the latest sound scientific information " and " not just my ideas. " Â Can you

provide us a reference to this scientific information which, by your own

definition, is neither your book itself, nor the Soviet Sports Review. Of course

you also state, " You may believe that the science of running has gone beyond

what we knew back in the 80s but it has not, " so I am not sure what " latest

sound scientific " information

went into your book in 2006 if nothing has gone beyond 1989.Â

You state that Weyandâ€™s conclusions are erroneous and that no one has proven

this statement to be wrong. Since the two of you disagree, donâ€™t you think it

is just a tad presumptuous of you to set yourself up as the one to determine

which one of you has been proven wrong.Â

I have no doubt that many readers have praised your book, but their opinions as

to whether it " truly explained what occurs in running " are a function of their

knowledge base at the time they read it.Â Ken admits that he once believed in

your book.Â

" Thus runners who have used the information have significantly improved their

running

capabilities and especially their running speed. " Â Unfortunately, this

self-serving statement can be attributed to every device, speed guru and program

out there, whether legitimate or not.Â It is just not relevant.

" This is understandable since you nor anyone else has supplied any

substantiation for disproving anything that I had written. " Quite frankly, I am

not certain there is much in your book aboutÂ running mechanics that hasnâ€™t

been called into question. Constantly stating that no one has proven you wrong

and that those who have are themselves wrong does not constitute facts in

support of a position, it is an unsupported, self-congratulatory conclusion.

You state, " I will use your statement in regard to stride length to prove this

point. I believe everyone will agree with Weyand that " applying greater forces

in opposition to gravity would increase a runners vertical velocity on takeoff,

thereby increasing both the aerial time and forward distance traveled between

steps. " But this is what a runner does NOT want to do. A runner wants more

horizontal velocity and wants to decrease aerial time. How does Weyand explain

this? "

Once again, you have missed the point completely.Â You have an idea of what you

think runners want to do based on how you think running occurs. When the

measurements of what is occurring donâ€™t match up to your preconceived notions

of what is ideal, you just claim no one understand the whole picture.

There is very little difference in swing time between elite sprinters and very

modest runners according to Weyandâ€™s study.Â Aerial time is already reduced

to an acceptable amount no matter what they do. Decreasing it further through

your technique interventions isnâ€™t likely to increase speed. Your original

claim was that there was no explanation of how vertical force created increased

stride length.Â You were given an explanation and jumped at the aerial time

reference, not understanding that as stride length increases (something I assume

you agree is important), aerial time does too.

There is really no further point in this debate. If you really think Weyand has

set sprint coaching back, you should make your views known in publications with

a wider reach than this board.Â Perhaps you should ask to speak at a seminar he

is at so you can thrash it out there. I would be interested in hearing or

reading an exchange between the two of you. Maybe you will then convince me that

you are correct, but so far you have not.

Jon Haddan

Irvine, CA

March 17, 2009

,

One distinction between the Finnish study you referenced and the Weyand study

might be that one was dealing with acceleration and the other with what is

happening at top speed. On the other hand, maybe different researchers are

coming to different conclusions. In a 2007 piece in The Journal of Experimental

Biology on the limits to maximum running speed on flat curves two of the authors

of the 3 m/s study you referenced, Chang and Kram, stated, " We have shown here

that vertical ground reaction forces were smaller at smaller radii and resulted

in slower sprint speeds. " This is in line with the Weyand study.

Although not relevant to the current discussion they went on to state that the

decrease was more than could be explained by a change in orientation of the

resultant ground reaction force vector to generate lateral, centripetal forces.

They propose that the need to stabilize different joints in the frontal and

transverse planes during the curve makes the inside leg ineffective at

generating the forces necessary to achieve straight path sprint speeds.

Jon Haddan

Irvine, CA

Subject: Re: Re: Mechanics of speed

To: Supertraining

Date: Tuesday, March 17, 2009, 5:04 AM

Hi Barry,

Firstly in reply to your questions.

1. " However, I am curious as to why you feel it is necessary to post research

regarding distance runners when the discussion at hand is about high speed

sprinting. "

It is at least curious that you bring this up, as you yourself refer to the

publication " The independent effects of gravity and inertia on running

mechanics " Chang, Huang, Hamerski and Kram. JEB 2000. In this study the running

velocity was 3 m/s.

In contrast, in the studies I refer to there's (at least partially) a focus on

maximum velocity running.

If you think my post is redundant I apologize.

I am not looking for research to back up dr Yessis. I think the studies do offer

more scientifical support to the discussion on 'mechanics of speed'.

I am interesting in the theme.

I do agree with dr. Yessis that new terms are and have been created in the past

that blur the discussion.

Also, pointing to a research without studying it thoroughly is a risky business.

I would claim that 90% or more of the research I've read has a weak point that

may negate their results and conclusions, or one needs to be carefull to

generalize the results.

For example, the scientifical support in your mail of 9 march is based on the

research mentioned earlier. At 3 m/s there's no need for optimalization of

contact time and/or technique. Other studies where GRF are measured at maximum

speed show different GRF patterns.

This discussion sometimes moves towards a yes or no competition, for example

s states: " My question to Dr. Yessis and those who believe similar

things, Is sprinting fast the most important exercise/drill a sprinter can do to

improve? Yes or No. It's that simple with the following caveat, if you say No

then you are a liar and a fraud. However, if you say Yes, then we all have met

on common ground and why their still may be differences we choose to achieve

them from a common starting point. "

In his book " Krafttraining und Bewegungsschneligke it " (in German, translation:

" weight training and velocity of movement, 1979) dr. Schmidtbleicher offers some

examples of athletes who did not or were not able to do much, in some examples

not any, sprint training, yet improved their personal best by several tenths of

seconds (and we're talking German champion level here). I've seen the same

things happening in practice. Still maximum sprint training is important for

tuning of the muscles to the highly specific movement and velocities, so

sprinting at maximal speed is not unimportant to me either. It comes down

to doing the right things at the right time. By stating " if you say no then you

are a liar and a fraud " I feel like entering a dictatorial state.

Cheers,

Huizing

Enschede

The Netherlands

____________ _________ _________ __

From: thefattys <barrybearpowered (DOT) com>

To: Supertraining@ yahoogroups. com

Sent: Sunday, March 15, 2009 6:33:07 PM

Subject: Re: Mechanics of speed

Hi ,

Thank you for posting this study!

It certainly has some interesting suggestions regarding the importance

of horizontal ground reaction force.

It would seem that two of the suggestions are very significant for

distance runners:

" This suggests that the short braking phase and use of elastic energy

are important factors both in economical

and high speed running in the group of young well-trained

endurance athletes. "

" This suggests that the horizontal component of ground reaction force is

more important in attaining high top running speed in distance runners

than the vertical component of it, since similar linear relationships

were not observed between vertical effective force and running speed,

and no significant correlation was observed between vertical force and

maximal running speed. "

However, I am curious as to why you feel it is necessary to post

research regarding distance runners when the discussion at hand is about

high speed sprinting. Could you give us the reason why you believe that

this research has merit to the current topic, especially since Dr.

Yessis has already stated earlier that he believes in the spring mass

model for sprinting?

Barry Ross

Los Angeles, USA

>

> Some articles that may be of interest in this discussion:

>

> -

http://www.kihu. jyu.fi/tuotostie dostot/julkinen/ 2007_num_ factors_re_ 1000\

0.pdf

>

> - Korhonen M, Mero A, Alen M, Sipilä S, Häkkinen K, Liikavainio

T, Viitasalo J, Haverinen M, Suominen H. Biomechanical and skeletal

muscle determinants of maximum running speed with aging. Medicine and

Science in Sports and Exercise (Accepted, published in April 2009).

>

Looking at the theme:

The higher the running velocity, the higher the vertical GRF. not very

surprising, as at a given running technique a person has less (contact)time to

change the vertical velocity. It's much easier to produce high vertical GRF when

bouncing with straight legs as compared to bouncing with knees bending, which

advocates to 'high running'.

According to some good-old research done by Hoshikawa et al (Medicine and Sport,

1973), who had people run on a treadmill at different velocities (up to 30 km/h)

and filmed their movement patterns, the running technique is different at

different velocities. Especially the swing leg is moved more backward and

forward (related to the center of mass (CM)) at higher velocities. In order to

lower the braking force at early contact, it would help if the foot approaches

the ground a the lowest horizontal velocity possible. It is easiest to

accellerate the foot backwards when it is in the air. On will reach a higher

backward velocity (related to CM) if one has more time to swing back, i.e. if

the foot is more in front of the CM. An extra help for this accelleration is the

functioning of the bi-articular muscles during the cyclic movement of the foot.

In my training I focussed on both improving body stiffness and using the SSC as

well as a pulling movement. I myself experienced the possibility of changing my

technique using technique exercises, and the effects of weight training, and I

experienced that most of my athletes were capable of changing their technique.

How much of any of the training stimuli I would offer depends on the individual

(build, physical background), on the developmental stage of this individual and

on the training goal.

Flojo was one of the first who showed that pulling can be effective.

2. " Could you give us the reason why you believe that this research has merit

to the current topic, especially since Dr. Yessis has already stated earlier

that he believes in the spring mass model for sprinting? "

March 18, 2009

Jon

We finally have total agreement -- further responses do not matter.

However, I must make a few corrections in your conclusions or

interpretations of what I said rather than taking my statements at face

value. This is where a good part of the problem lies.

For example I do believe in the spring mass model as I have stated. However

I never said that the spring mass model applies to sprint running. This is

your belief. The true spring mass model applies to jumping where you apply

a vertical force and have a vertical return. I do not believe it applies

to running except possibly in the initial loading that occurs on touchdown,

but not in regard to vertical forces being the only force applicable at this

time as you and others maintain.

But if you explain running by using the spring mass model you should be able

to explain how the vertical forces translate to horizontal forces. If not

then you do believe that the runner looks like someone on a pogo stick going

up and down as he travels down the track.

When I spoke of the knee drive I made no mention of limb speed in comparison

to other runners. But yet, you continually make a big deal of this. It is

immaterial in regard to the force the knee drive can generate. You state

that linking the thigh drive with the pushoff is a flawed assumption. It is

not an assumption it is fact!

I believe that the problem is that you (and Weyand) try to explain

everything that happens in running on the force produced on touchdown. But

yet if you study biomechanics you'll know that measurement of forces

generated or forces produced must be synchronized with what the runner is

doing during the running stride. In other words, what is the exact position

of the body and or limbs when the force is produced? What transpires during

the force production?

For example, the body of the runner is well out in front of the support foot

when ground contact is broken and it is more or less directly above the foot

when initial contact is made. These changes are very important in regard to

the return of force and the direction in which the force is applied. It

also explains the loss of force at the end of the phase of amortization.

This however has not been taken into consideration.

You keep harping on studies to explain your position. You should be able to

explain your position and use a study only to corroborate some of the things

that you say. Answering a question by citing a study is not answering the

question. It only adds more " facts " to the issue that tend to confuse the

issue, not clarify it. Thus when I say you have not answered how vertical

force is translated to horizontal you avoid the answer by merely citing a

study. This does not show understanding, it implies a cover up for lack of

understanding.

Yessis, PhD

Professor Emeritus, CSUF

President, Sports Training Inc.

www.DrYessis.com <http://www.dryessis.com/>

March 18, 2009

Hi ,

Research regarding distance runners has a long history while sprinting

has, until recently, a relatively short and narrow research base. The

research you presented is contrary to a much wider body of researchers

than that of Weyand et al. and thus is highly questionable at this time.

I chose to use the Chang, et al. study for several reasons:

1. Their previous research indicated that vertical forces generated

against the ground can be attributed entirely to effect of gravity

alone.

2. They stated that the generation of horizontal braking force followed

by horizontal accelerating force is universal to all running animals,

yet Dr. Yessis denies the existence of braking force by his explanation

of " paw-back " .

3. The researchers stated, " Although we expected the horizontal

impulses generated on the ground to be influenced by mass and not by

weight, inertia had a smaller effect on the generation of horizontal

forces compared with gravity " . Dr. Yessis errantly believes that

horizontal force alone drives the runner forward.

4. The researchers admitted that, contradictory to their intuitive

reasoning, horizontal forces were not generated in proportion to overall

mass. Even though the horizontal forces were less than overall mass,

all running animals show a universal pattern of braking and

accelerating. Dr. Yessis denies braking force exists during paw-back.

5. They provided that analysis of the resulant force vector of each

runner could explain why gravity rather than inertia greatly effected

horizontal forces. In fact, they suggest that " the alignment of the

resultant force vector with the leg during times of high force

genertaion, may be a universal mechanism for minimizing net muscle

moments, muscle forces ad metabolic costs during running " .

While it should be understood without saying, denying or purposely

obfuscating all research is risky business. When one concludes that

their work is exempt from research and/or public scrutiny, it's time to

look for other alternatives.

This is not pointed at you !

It's pointed toward those who believe that their training protocol need

not be examined simply because it's their protocol.

It's also pointed to those who make statements then retract their

statements when convenient.

Barry Ross

Los Angeles, USA

> >

> > Some articles that may be of interest in this discussion:

> >

> > -

> http://www.kihu. jyu.fi/tuotostie dostot/julkinen/ 2007_num_

factors_re_ 1000\

> 0.pdf

> >

> > - Korhonen M, Mero A, Alen M, Sipilä S, Häkkinen K,

Liikavainio

> T, Viitasalo J, Haverinen M, Suominen H. Biomechanical and skeletal

> muscle determinants of maximum running speed with aging. Medicine and

> Science in Sports and Exercise (Accepted, published in April 2009).

> >

>

> Looking at the theme:

> The higher the running velocity, the higher the vertical GRF. not very

surprising, as at a given running technique a person has less

(contact)time to change the vertical velocity. It's much easier to

produce high vertical GRF when bouncing with straight legs as compared

to bouncing with knees bending, which advocates to 'high running'.

> According to some good-old research done by Hoshikawa et al (Medicine

and Sport, 1973), who had people run on a treadmill at different

velocities (up to 30 km/h) and filmed their movement patterns, the

running technique is different at different velocities. Especially the

swing leg is moved more backward and forward (related to the center of

mass (CM)) at higher velocities. In order to lower the braking force at

early contact, it would help if the foot approaches the ground a the

lowest horizontal velocity possible. It is easiest to accellerate the

foot backwards when it is in the air. On will reach a higher backward

velocity (related to CM) if one has more time to swing back, i.e. if the

foot is more in front of the CM. An extra help for this accelleration is

the functioning of the bi-articular muscles during the cyclic movement

of the foot.

>

> In my training I focussed on both improving body stiffness and using

the SSC as well as a pulling movement. I myself experienced the

possibility of changing my technique using technique exercises, and the

effects of weight training, and I experienced that most of my athletes

were capable of changing their technique. How much of any of the

training stimuli I would offer depends on the individual (build,

physical background), on the developmental stage of this individual and

on the training goal.

>

> Flojo was one of the first who showed that pulling can be effective.

>

> 2. " Could you give us the reason why you believe that this research

has merit to the current topic, especially since Dr. Yessis has already

stated earlier that he believes in the spring mass model for sprinting? "

>

March 19, 2009

A point of clarification for forum members:

In a message dated 3/18/2009 1:11:31 P.M. Central America Standard T,

dryessis@... writes:

If not

then you do believe that the runner looks like someone on a pogo stick going

up and down as he travels down the track.

The following is from R. McNeill 's book, The Human Machine: How

the Body Works...

" Running is not like a pendulum, but like a bouncing ball or a child on a

pogo stick. "

is probably the most respected authority on human and animal

locomotion in the world.

The question posed to Jon Haddan could be posed almost universally to those

engaged in locomotion research, and those who understand the spring mass

model. Yes, running is like a bouncing ball or a child on a pogo stick. It is

not just Jon's 'belief.'

also noted the following:

" A large part of the ankle movement that we see while the runner's foot is

on the ground is due to stretching and recoil of the Achilles tendon. The

tendon stretches enough for its role as a spring to be very significant. "

Ken Jakalski

Lisle High School

Lisle, IL USA

March 20, 2009

A bouncing ball moving in horizontal direction will start to rotate...

Cheers,

huizing

The Netherlands

________________________________

To: Supertraining

Sent: Friday, March 20, 2009 4:19:35 AM

Subject: Re: Mechanics of speed

A point of clarification for forum members:

In a message dated 3/18/2009 1:11:31 P.M. Central America Standard T,

dryessisdryessis (DOT) com writes:

If not

then you do believe that the runner looks like someone on a pogo stick going

up and down as he travels down the track.

The following is from R. McNeill 's book, The Human Machine: How

the Body Works...

" Running is not like a pendulum, but like a bouncing ball or a child on a

pogo stick. "

is probably the most respected authority on human and animal

locomotion in the world.

The question posed to Jon Haddan could be posed almost universally to those

engaged in locomotion research, and those who understand the spring mass

model. Yes, running is like a bouncing ball or a child on a pogo stick. It is

not just Jon's 'belief.'

also noted the following:

" A large part of the ankle movement that we see while the runner's foot is

on the ground is due to stretching and recoil of the Achilles tendon. The

tendon stretches enough for its role as a spring to be very significant. "

=============================

March 20, 2009

Ahhh, but a person on a pogo stick will not!

A bouncing ball never uses the paw-pack method to generate horizontal force.

It's time to bury some of the old, old concepts of running since modern

research is far ahead of most practitioners.

Barry Ross

Los Angeles, USA

======================================

From: Supertraining [mailto:Supertraining ]

On Behalf Of Huizing

Sent: Friday, March 20, 2009 4:04 AM

To: Supertraining

Subject: Re: Mechanics of speed

A bouncing ball moving in horizontal direction will start to rotate...

Cheers,

huizing

The Netherlands

________________________________

From: " CoachJ1@... <mailto:CoachJ1%40aol.com> " <CoachJ1@...

<mailto:CoachJ1%40aol.com> >

To: Supertraining <mailto:Supertraining%40yahoogroups.com>

Sent: Friday, March 20, 2009 4:19:35 AM

Subject: Re: Mechanics of speed

A point of clarification for forum members:

In a message dated 3/18/2009 1:11:31 P.M. Central America Standard T,

dryessisdryessis (DOT) com writes:

If not

then you do believe that the runner looks like someone on a pogo stick going

up and down as he travels down the track.

The following is from R. McNeill 's book, The Human Machine: How

the Body Works...

" Running is not like a pendulum, but like a bouncing ball or a child on a

pogo stick. "

is probably the most respected authority on human and animal

locomotion in the world.

The question posed to Jon Haddan could be posed almost universally to those

engaged in locomotion research, and those who understand the spring mass

model. Yes, running is like a bouncing ball or a child on a pogo stick. It

is

not just Jon's 'belief.'

also noted the following:

" A large part of the ankle movement that we see while the runner's foot is

on the ground is due to stretching and recoil of the Achilles tendon. The

tendon stretches enough for its role as a spring to be very significant. "

=============================

March 20, 2009

wrote:

" A bouncing ball moving in horizontal direction will start to rotate... "

***

..... due to the frictional component of the ground reaction force.

But what thats got to do with running escapes me!

Pat Squire

Edinburgh UK

March 20, 2009

The author of the previous mail compared a runner with a bouncing ball.

Also: imagine that only a vertical force would exist. At least during part of

the contact time the CM is in front of the foot that is on the ground. This

would create a forward rotation of the body.

This would not happen if the GRF vector would pass through the CM.

Cheers,

Huizing

The Netherlands

________________________________

To: Supertraining

Sent: Friday, March 20, 2009 7:46:32 PM

Subject: Re: Mechanics of speed

wrote:

" A bouncing ball moving in horizontal direction will start to rotate... "

***

..... due to the frictional component of the ground reaction force.

But what thats got to do with running escapes me!

==============================

March 20, 2009

Hi

Is what you are implying, that by increasing the total force you thus

increase its vertical and horizontal components. The angle/direction as

well as the magnitude of the applied force will thus effect the horizontal

and vertical components.

In the same way that a pogo stick jumper leans more forward to get more

speed :-to a maximum after which insufficient height is achieved to allow

more speed that is the pogo comes to ground to early to effectively use the

propulsion force to its fullest and the spring is not loaded as much because

of the attitude of the spring to the ground. If the analogy of pogo stick

transfers to the runner in this way, which it seems to as the leg is best

used to store and amortise the stored energy in the time frame that

sprinters have ground contact. (it seems that little else could happen in

that short time), then training the leg to behave more spring like might be

the best training for maximising high speed running. But that the angle of

the actual force (that we broke down into its components) is important to

and possibly a technique issue that needs addressing.

Regards

Nick Tatalas

Johannesburg

South Africa

2009/3/19 Flory

>

> > This seems contrary to the assumptions of many who see acceleration

> > as primarily a horizontal force event and might concede that

> > vertical forces help maintain the speed initially created

> > horizontally.

>

> The _only_ force vectors that can cause horizontal acceleration, or

> deceleration, are _horizontal_ force vectors. The only effect vertical

> force vectors _can_ have is to increase or decrease the friction of

> the surface in contact with the ground. There by they can increase or

> decrease the amount of force that can be applied without contact

> surface slippage. The laws of the physics of motion aren't specialized

> for runners. They are the same for runners as for cars and pogo

> sticks, bullets and balls. In all these cases the main forces that

> interact with the ground are usually at an angle to the horizontal,

> but, by definition, the vertical vectors are vertical and the

> horizontal vectors are horizontal and neither one can cause

> acceleration in any direction except that of the vector.

>

> Fair winds and happy bytes, Dave Flory, Flower Mound, TX, U.S.A.

> --

> Speak softly, study Aikido, & you won't need to carry a big stick!

>

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Re: Mechanics of speed

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