Re: Does sports science research influence practice?

[Guest guest]

> This should suffice for now. I will look forward to your and anyone

> else's responses to these questions. To be sure we stay on track,

> please refer to the number of the question so that we can we can

> more easily follow your discourse. Then we will see if my comments

> are opinion and if Weyand truly understands running.

>

> Regards,

> ~~~~~~~~~~~~~~~~~~~~~~

> Yessis, Ph.D

> President, Sports Training, Inc.

> www.dryessis.com

>

> PO Box 460429

> Escondido, CA 92046

> ~~~~~~~~~~~~~~~~~~~

***

Hi Dr. Yessis,

Here are my matching responses, as you requested,to your questions:

(1) Yes, limb speeds can be the same. You can see this in action by

going to www.bearpowered.com/resources, then clicking on The Saga of

2 Runners. What you will see is that both runners are landing at the

same time, stride after stride, yet in a 100m race the faster of the

two is faster by 1 meter per second faster. If you watch the grounded

foot of each runner, you will see that the faster one's foot leaves

the ground increasingly earlier than the other. This allows more air

time to reposition his leg for the next stride. Weyand's study

mentions precisely what you see in the video, " Faster runners applied

greater forces during briefer contact periods, whereas slower runners

applied lesser ground forces during longer contact periods. "

The faster runner needs no more time to reposition limbs then slower

runner uses.

Interestingly, stride frequency does increase ( " The large

sensitivity of top speeds to small differences in the mass-specific

support forces applied to the running surface resulted from the

positive effect of support forces on maximal stride frequencies. "

Weyand, et al.). What is the cause of the faster stride frequency?

" Stride time (measured in s) was defined in accordance with Heglund

et al. as the time between consecutive footfalls of the same foot "

and " Stride frequency was determined from the inverse of the total

stride time (1/total stride time). "

Stride frequency, as determined above, improved because of the

shorter contact time of the faster runner. All of this is driven by

mass specific support force.

In answer to your question regarding distance covered, yes the faster

runner is covering more ground as he easily pulls away, but he

doesn't have to move limbs faster to do so. It's not individual limb

speed that's critical, it the speed of the body that must be

considered.

(2) You are correct in saying that force equals mass times

acceleration.

Where the problem lies for most is in recognizing that gravity pulls

the runner back to the ground and would continue accelerate the

runners mass until it hits terminal velocity (which won't happen to a

sprinter, so it's not really in issue here). In other words, the

airborne runner is now no different than any falling, accelerating

mass.

The opposite side of the amount of force created by the accelerating

mass of the runner striking the ground is what ground reaction force

plates measure. Newton's 3rd Law states that this measured force must

be equal to the force the runner hits the ground with. That force is

equal to 3 times bodyweight or more. The runner did not create this

force through chemical muscle power, but instead by merely hitting

the ground as a falling, accelerating mass. That is pure,

unadulterated physics.

Ground support force is the amount of force the runner must apply to

the ground so as not to collapse from the impact (support) and to

take maximum advantage of the force that will be returned by the

ground (Newton's 3rd law). This force applied by the runner is

derived primarily isometrically, so there is minimal change in muscle

length as well as minimal limb movement in creating force.

How does this equate to greater strength and less mass?

Let's assume that our runner is 150 lbs and hits the ground with 450

lbs of force against the mass of the earth. The earth is going to

return 450 lbs of force against the runner's mass. The runner's force

is not going to move the earth's mass but the earth's force is

certainly going to move the runner's mass since it is 3 times greater

than the mass of the runner. Now, up the ante with an elite sprinter

creating force equal to 5 x bodyweight and that sprinter is going to

be moving a lot further down the track. How can we know this? Because

Weyand's study showed that, " Average support forces of runners

applied to the running surface at top speed were systematically

higher for faster runners. "

(3) After digesting the above, it should be clear that strength

doesn't create ground reaction force, but rather accelerating mass

does. Ground reaction is just that, reaction to the force hitting it.

Since support force is largely isometric, joint actions are not the

prime points of focus for improvement. In addition, it should be very

clear from watching the video of the 2 runners that knee flexion is

minimal and therefore could not create the massive forces measured by

GRF plates. This goes back to the " test " I proposed to the members of

this forum.

(4) The deadlift is not better than its closest neighbor, the squat,

as far as maximizing strength, but it has some essential factors that

make it more efficient and effective for the training required. I'm

not

going to go into all those reasons. That being said, specific joint

action is not where strength is displayed for all of the reasons

stated above. Specificity of training for running is not centered

around joint movement but on increasing isometric strength, bone

density, muscle density, tendons etc. for increasing support force to

offset gravity. All of these are necessary as support and not the

creators of force. Ballistic lifts don't cut it here either.

(5) While the Pose method at least mentions gravity as relevant, it

barely touches on the importance of it. The system also relies on

training elements of running by means that simply don't work. I

passed on the Pose long ago.

It's quite simple to explain how vertical and horizontal influences

work together in sprinting (Interesting how that question is always

framed as how vertical can be responsible for horizontal. How about

we reverse the question: How does one get in the air by pure

horizontal forces?). The beginning of a run must be dominated by the

horizontal because it is necessary to use chemical muscle mechanical

work to overcome inertia by pushing the mass forward rather than

upward. As speed increases, the runner begins to elevate in order to

allow gravity to begin the work described above, that is, using the

force of gravity to create ground reaction force as well as creating

and storing elastic energy used for impulse in the vertical

direction. The vertical direction doesn't mean straight up, it means

that the runner will use a vector that allows them to trade the high

metabolic cost of chemical muscle mechanical work for the lower cost

of ground reaction force and effective impulse from elastic energy.

The horizontal force at take off is equal to the braking force at

touchdown, assuming no wind. This is true because of Newton's 3rd

law. The braking action is critical in maintaining the horizontal

portion of the vector. Here's why: The runner is traveling at a high

rate of speed while in air. At toe down, mass is just behind the

grounded foot. The foot stops moving forward at that point, but the

torso keeps moving horizontally, especially since the majority of the

mass is around hip height which creates a catapult-like effect. If

one drives a car at 25 miles per hour, but foolishly forgets to put

on a seat belt, what happens if the car hits a wall? The seatbeltless

person continues to move horizontally at the same speed the car was

moving until they hit something solid.

As mass crosses over the grounded foot, ground reaction force and

impulse from the elastic energy created from eccentric contraction

puts the runner back into their running vector. Ultimately, the

runner slows down as muscles tire from the isometric work and can no

longer create and release sufficient elastic energy.

(6) Your statement here was: " In relation to ground reaction forces,

you state that they are greatest halfway through the support stance

time and mostly gone after two-thirds of this time. "

In all due respect Dr. Yessis, this is what the measurements show and

there is no way to get around it. In fact, if you go back to

www.bearpowered.com/resources and click on Force Plate Fellow (circa

1970's or so and found on the internet), you will clearly see that a

ground reaction force plate only shows a measurement of force when

force is applied to it. It is also clear that merely crouching down

for the counter motion jump creates force because the body is

accelerating towards the plate (mass x acceleration=force). When the

man begins to move upward, force begins to disappear because he is no

longer accelerating downward. At the moment just before he lifts off

the ground, how much force is being applied to the ground? Virtually

no force is measured so there is virtually no force applied to the

ground when the jumper jumps. Isn't this where peak push off forces

should show if they exist?

In contrast, look at the 1 sec point where he begins toe down.

Within .2 seconds of toe down, force peaks, then starts to drop. This

is exactly what I described in (3) above. The answer to your

question, " How does this leave any force for the push-off? " is clear:

It doesn't leave any force for push off because there is no force

applied to the ground at push off. It also means that you're were

absolutely right when you say, " If this is true there is no need for

ankle extension. "

What you're seeing as ankle extension is caused by the reaction of

the previously grounded foot to the eccentric contraction of the calf

muscles and Achilles tendon as the man moves up from the counter

motion. The same reaction can be observed by pulling one forefinger

back as far as possible with the other forefinger, then releasing

it. It isn't chemical muscle power that snaps the just-released

finger forward, just as it isn't chemical muscle power that extends

the ankle at toe off. Pictures aren't proof of push off either

because they don't show force.

Proof that force is created at push off must be shown clearly on GRF

plates if that concept is to viable for training. Until that

proof is made available, exercises claiming to help create force at

push off should be set aside.

(7) I did not mean to imply that knee extension is the key factor in

supplying the speed in running. A small bend in the knee is necessary

to activate the spring part of the spring-mass model. A straight leg

would not allow for an effective spring action. It is the spring-like

action and GRF that supplies the speed in running.

Weyand truly understands running, as would his peers attest along

would the multiple citations of his work in the research papers of

others. Not one locomotion scientist has come forward to contend

against the research paper in the 6 years since publication of the

paper we've been discussing. Weyand's paper is ground breaking in its

analysis of running speed, mass-specific force, the effects of force

application, and much more.

And finally, there is always a danger in using pre-suppositional

thinking in order to review the merits of a " new " proposition. All of

us should be aware of that when we examine anything new, since we've

all been guilty of relying on something we thought to be true as the

bench mark for looking at the efficaciousness of a new approach. It

took 3 years for me to get through the fog of my pre-suppositions

regarding sprinting and sprint training before I could fully

understand the vast amount of research regarding the spring-mass

model and a strength training routine that fits within in the

trainable aspects of the model.

Regards,

Barry Ross

Los Angeles, California.

[Guest guest]

Hi Dr. Yessis:

Over the past two years I’ve analyzed through motion analysis software over

seventy athletes ranging in speed from 7.5 to 9.5 meters per second, and in

none of these athletes do I see any evidence of increased limb speed prior to

impulsion. I have even analyzed an athlete whose coach insists he was taught

the correct pawback technique, yet the analysis was the same. These

findings are consistent with the fact that force plate studies never reveal

peak

forces occurring in the first third of the stance phase, which one would expect

to be the case if the limb were indeed accelerating back to the track right

up to the point of touch down.

We have placed several of these SiliconCoach reviewed images on Barry Ross’s

website.

My questions to you would be: Why is the limb slowing prior to impulsion,

and what is the speed of the torso at the point of impulsion? This second

question is critical to understanding why there is no push-off in the

conventional sense (muscle mechanical work) once a runner is up to speed, and

why

locomotion researchers often use the superball analogy to explain the spring

mass

model.

In every force plate analysis I’ve reviewed, forces peak prior to mid

stance, not in the first or third segments. If there were a conventional

push-off

at top speed, one would expect that an athlete running on ice or over a carpet

or floor (with baggies on his or her feet as offered) would slip.

If you review the “Ice Man†clip 1 on the site, you'll note Dan Fichter

struggling to stay balanced during acceleration.. However, in clip 2, you’ll

actually see him running from a black mat onto ice for a full stride once he's

up

to speed. He does not slip.

As Dr. Weyand noted in my first visit to the Concord Field Station

locomotion lab: Nearly everyone, scientists and others, have believed that the

faster

humans or animals run the more rapidly their muscles contract -this is not

true. Because support forces are all important, regardless of speed, and

because muscle force production is maximized by isometric (i.e. no shortening)

contractions, both from a design and function standpoint, the optimal

shortening

velocity for muscle during level running is zero (the left-hand side of the

f-v curve, not the right hand side where force production approaches zero and

the runner would collapse to the ground or need 10-100 times the amount of

muscle available to support the body's weight).

It took visits to locomotion labs at both Harvard and Rice University

before this began to make sense to me. Further, since no peer reviewed study

to

date has challenged Weyand's data or its basic findings and conclusions, and

since the swing time data has been corroborated by other noteworthy

researchers in the field, I believe we are neither misguided nor mistaken in

the

approach we've taken to these mechanics issues.

Those on the forum who also grasp these principles have spent considerable

time either directly communicating with the researchers, e-mailing them with

questions, or attending one of their seminars. And that was the point of our

initial response to this thread: that from our experience we have found good

lines of communication between the scientists and the practitioners.

Further, what the scientists have shared with us has influenced the way we

train our

athletes.

Ken Jakalski

Lisle High School

Lisle, IL

[Guest guest]

>

> Have either of you (Dr Yessis/Barry) and used this information to

> coach sprinters on the track and/or in the gym, and if so, how is

> your information applied? I'm curious as to the application of

the

> technicalities brought forth in this debate.

>

> [Mod: Do search the archives as both members have offered some

wonderful insights in the past. Additionally, it may be worth

searching both respective websites www.bearpowered.com and

www.dryessis.com - much of the information is available for free]

>

***

Yes, the most notable would be Allyson Felix (11.29, 22.11) when she

was in high school, as well as working with Olear (ll.43,

23.31) last track season. She is currently a freshman at the

University of Southern California. I've worked with hundreds of

others, primarialy high school athletes, but I've worked also with

college, elite and professional athletes in a variety of sports

including tennis and baseball.

Barry Ross

Los Angeles, Calif.

[Guest guest]

Hi Dr. Yessis:

Here are some comments, observations, and conclusions:

<The force plate platforms you speak of measure only vertical forces,

not horizontal, which are the most important to a runner. This is

why you only see a part of the total picture.>

This is incorrect. Force plates are designed to measure force and they do

so in all three planes: vertical, horizontal and lateral.

I disagree with your analysis. Push-off in this conventional sense (an

active muscle shortening) does not occur. The athlete is rotating over the

grounded foot, and contact time actually decreases with increases in speed.

All

force studies will show the peak force occurring in the middle third of

stance. If there were an active push-off as you are suggesting, we would

expect

to see peak force in the last third phase. This is not the case.

In a previous post, I asked you to analyze the speed of the center of mass

over the grounded foot at top speed. With contact times less than

nine-hundredths of second, and with a mass rotating over that grounded foot,

explain how

the athlete is achieving a push-off. Again, I’ll ask you to show evidence as

to how this occurring.

<In regard to your ice runner, he also did not have a strong push-

off. If you disagree, why do sprinters wear spikes? >

That’s the point. There is little to no push-off in the conventional sense

once a runner is up to speed. Note how Dan slips during acceleration. That

does not occur one he’s up to speed. How are you able to visually asses or

identify the strength of his push-off? Could you tell that athlete’s speed

from that image? This is the key to our discussion relative to spring

mechanics at top speed. Push-off in this conventional sense does not occur.

The

athlete is rotating over the grounded foot, and contact time actually

decreases with increases in speed. All force studies will show the peak force

occurring in the middle third of stance. Regarding spikes: Runners wear spikes

because they are light and will provide grip when the center of mass of forward

of the drive legs during acceleration. They also have plastic plates which,

despite the plate design configuration, might cause slipping during

acceleration were the spikes not present.

<Where is the data to support that support forces are all important?

They play a critical role in economy but not force production. Also

isometric strength does not fit in to the spring model.>

Locomotion experts consider the spring model to be an explanation for the

isometric behavior observed. (Note et. al, 1997) The data is in the

study itself. The title of the study makes that quite clear: Faster top

running speeds are achieved with greater ground forces not more rapid leg

movements.

I also believe you have a somewhat different interpretation of the spring

mass model. Runners behave just like springs under steady state conditions.

Essentially, the relationship between the force on the ground and the

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

contact

period. Springs by definition have the same relationship between force and

displacement on compression and release or stretch and release - and this is

how

the body behaves during running. Nearly all the mechanical energy is

recycled over the course of the stride so the active muscles do not need to

shorten

or perform work; they simply need to generate support forces against the

ground to support the body's weight.

<You must also differentiate between muscle contraction speed and

limb speed. They are not the same and I never questioned muscle

contraction speed. Nor did I question the findings in the Weyand

study. I questioned the interpretation of the data. The

conclusions are not supported by the data. Note that most of them

are based solely on vertical forces -- which are a small part of the

total picture.>

During constant-speed running, the peak vertical ground reaction forces are

typically 5-10 times greater than the peak horizontal forces. (Munro, ,

J. of Biomech 1987)

<For example, why are you having your runners do the deadlift? How

did you conclude this from the study? You disregard the pawback

movement but this exercise develops the same muscles in the same

joint action but not with the same moving part? Is it possible the

runners are getting better regardless of what you think is happening?>

We deadlift because, after reading Barry’s book, I began my own project to

assess the effectiveness of the protocol outlined in that book. I was

impressed with the results.

I disregard the pawback because I see no evidence of it occurring even in

athletes correctly taught the ‘technique.’ I would expect that, were it

indeed occurring, I’d see it in at least one of over seventy-five sprinters

ranging from 7.5 to 9.5 meters per second. How can the pawback develop any

muscles

when it does not occur?

<For a much better understanding of what takes place in running I

once again suggest you read and perhaps reread, Explosive Running

and the studies done by the Soviets. Many of the latter are

reported in the Soviet Sports Review (Fitness and Sports Review

International). After reading these sources compare their findings

and conclusions to what you have interpreted. You should be able to

resolve most if not all, differences if you truly understand what

occurs in running.>

For a much better understanding of running, I recommend that you read or

re-read the Weyand study. I offer that you could not continue to pose the

questions you

are posing if you had actually read and understood the study you are so

committed to discrediting. With all due respect, I have four of your books,

have

read Explosive Running three times, and have attended two seminars where you

spoke. I even took Explosive Running with me on my visit to Harvard’s

research

lab. The techniques you mention in the book are not supported by the images

in that book. The problem that I have with those photos has nothing to do

with the quality of the camera, the frame rate, or the sequencing. My concern

is that the images cannot be analyzed through any available biomechanics

software. The camera is not fixed (it pans as the runners are moving) and

there

is no metric referent point in order to analyze the mechanics that you point

out the photos are revealing. Can you tell me the forward speed of the

athlete over his grounded foot? That is what the I wished the photos in

Explosive

Running would have revealed, because that would have at least explained how a

conventional push-off could be greater than the speed that athlete has

achieved as he moves forward over his grounded foot.

Basically, the position you establish in Explosive Running is your

conjecture and speculation. No position or velocity data appear in your book to

support your claims for pawback. Peer reviewed papers cannot be published

without

meeting this data standard.

<You state that you and others have had great intercourse with the

reseachers. This is terrific and as it should be. However, how,

sound rational for what the researchers shared with you translated

into effective training sttill leaves much to be desired.>

I wouldn't say I had great intercourse with the researchers, but at my age I

do appreciate most great intercourse. Humor aside, I respect that you

believe a pawback and a push-off are the things that change mechanically as

runners

reach top end speed. I don’t agree.

If you are correct in that the conclusions of the JAP study are not

supported by the data, I would offer that you are clearly in the minority. No

one in

the scientific literature has challenged the findings/interpretations, and no

one at USATF (including Dr. Mann) has voiced the concerns you have. Either

these individuals have actually grasped the implications of the study or, as

you contend, they have not read the right sources (Explosive Running, Soviet

Sports Review) in order to truly understand what occurs in running.

However, I would not compare these works to the research currently available

in the scientific community. These works are not peer reviewed and are not

close to being held to the same high standard. For the reasons I cited

above, I think it is inappropriate to counter a peer reviewed study published

in a

well respected journal with material that, as in the case of Explosive

Running, is basically one man’s opinion.

You can also draw the conclusion that what we have found to be effective

training leaves much to be desired. However, there are some clear points from

the majority of contemporary locomotion studies that cannot be ignored.

Nearly all of us, even the scientists and biomechanists, have believed that the

faster a person runs the more rapidly their muscles contract -this is not true.

Because support forces are all important, regardless of speed, muscle force

production is maximized by isometric (i.e. no

shortening) contractions.

The central point in all of this is that at top speed the net work performed

by the athlete is practically zero. What little is performed is achieved

largely passively so that what the muscles are doing mechanically is lots of

force generation and very little shortening work.

I have also done as you suggested, and compared the findings and conclusions

in Soviet Sports Review, and I must admit that I had many questions

unanswered as a result of their technique recommendations and insights. For

example, how was it possible that an athlete without forearms to swing

effectively

or ankles and feet to pawback effectively could run 22.94 on my track? The

conventional research to which you have alluded did not explain this for me,

nor could it explain why athletes on my team with what conventional wisdom said

was ‘poor technique’ were some of the fastest sprinters on my squad. The

Harvard research did. Perhaps that is why it is easy for me to suggest that

this research is groundbreaking. I have received more answers now than I did

in my first twenty-five years of coaching. And that again, was the point of

my initial response to this current thread— that contemporary sports science

research has indeed influenced my approach to practice and training, because I

’ve found other coaches who have based their training protocols on good

research. I had no wish nor desire to enter round three of a debate on the

interpretations of the Weyand study.

If indeed we do not " truly understand what occurs in running, " and that such

insight is available through careful reading of Explosive Running, then I

offer that I could send you clips of various runners sprinters this spring, and

based upon your visual observations of technique flaws, which you should

have no problem determining, tell me which of these athletes is the fastest. I

will send the speeds of each of these runners to the moderator and allow you to

rank

their order and approximate top speed.

Since this is now the third time this issue has come forward on the forum,

and the third time we’ve addressed these issues, I’d ask the moderator to

end

the thread. I also feel it is somewhat unprofessional that we be subjected

to consistent reminders that enlightenment on these mechanics issues must come

from a particular source, Explosive Running, when for the reasons various

members have mentioned in the past we feel that work has not provided us with

the corroborative data to support the opinions expressed in the text.

I concur with Jon Haddan. We have once again established that you disagree

with Weyand and other published locomotion scientists and studies. Can we

move on? Further discussion is not going to change anything.

Respectfully,

Ken Jakalski

Lisle High School

Lisle, IL

..

[Guest guest]

" I stand by my comments regarding the mass-spring

model concept. What you [barry Ross]don't understand

that this model is used to explain what happens in

jumping . It is sometimes used to explain a very

small part of running. And then, only for a

comparison. "

**

<<<That statement is inaccurate and your previous

statement that horizontal forces are much more

important than vertical forces in running simply does

not match up with the model that you now claim to

support. Perhaps you could actually quote from your

book where you state that the spring mass model is the

generally accepted explanation for how humans run.

I don't see the relationship between your having

introduced the works of Verkhoshansky or been an early

advocate of plyometrics and the topic at hand. I also

don't see what the similarity in exercises between

your book and his has to do with the topic or what it

is supposed to mean.

If, as you say, you are one of the few Americans that

truly understands the Soviet training system, fine.

What does that have to do with the Weyand study?

The fact that Verkhoshansky's training methods are

" far removed from any of the conclusions drawn by the

Weyand study and its' supporters " does not mean

anything except that the supporters of the Weyand

study do not follow such methods. But,

you keep stating that no one has been able to " state

in specific terms how the findings from this study are

applied. " Didn't you just imply that the supporters

must be using different training methods than

Vekhoshansky? How else do you conclude that his

methods are far removed from their conclusions? Or

are you suggesting that the supporters who have drawn

conclusions far removed from Verkhoshansky's training

methods are nonetheless still using those methods?

Could you please explain your statement " if you read

my posts carefully you would know that I never

questioned Weyand's findings " in light of your

statement " Speed of the body is dependant on limb

speed and the push-off. …This is pure physics, not

opinion " and the title to Weyand's study " Faster Top

Running Speeds are Achieved with Greater Ground Forces

not More Rapid Leg Movements "

If as you claim it is the interpretations not the

findings that you disagree with then what is it about

the interpretations of Weyand's study that you

actually disagree with?

You state, " Reading from you and others, the

implication is that the Weyand study is a ground

breaking study and one of the greatest things that

ever happened in the advancement of running. " I

certainly never made any such statements. However, if

you do not disagree with the study (as you say) and it

is not ground breaking, then it must be old news.

What about it is old news?

Your comparison of the Weyand study to Arthur is

off the mark. designed a product and came up

with studies to support its marketing. Weyand is a

research scientist. No similarities at all.

You know full well that certain people are applying

the findings (which you claim you agree with) by

limiting their lifting to one basic lift (far removed

from Verkhoshansky's training methods), and largely

ignoring issues of form (which is heavily emphasized

in your book).

I did not state that a book written for coaches and

runners (your characterization of your own book)

should necessarily be judged by a lack of references.

I was not judging your book in the context of its

originally intended audience, but in the manner in

which you have currently been using it. A book

without references is really just one person's

opinions. It should not be cited by the same person

who wrote it as the sole authority for rejecting a

published study or its interpretations. Having given

your opinion, which you are certainly free to do.

Since you asked about track books with references, let

me suggest to you Better Training for Distance

Runners " by E. Marin & N. Coe or

the Jess Jarver series. If you want a general

training book with references, how about

Supertraining. The Lore of Running is another book

heavily footnoted. s Running Formula is based

on a lot of research. My recollection is that Irv Ray

& Tony Benson's book cites the work of Jack s

and others. All of these books are well known by

people in track circles. Whether they are the most

popular I couldn't say. Barry Ross wrote a book that,

as I recall, references numerous studies.>>>

***

I won't bother responding to most of your comments because you have

read things into my comments that weren't there and discussing them

would be impossible. I do however stand corrected on some of the

popular books. I should have said most.

It also looks like I did not connect the dots to my mention of

Verkhoshansky. You should know that Fred Wilt and I introduced what

we know as plyometrics. Fred came up with the term and believed

this was the secret to the success of Soviet runners and jumpers. I

came up with the studies and articles supporting plyometrics from

the Russian literature and from Verkhoshansy himself.

I was the first to defend and support plyometrics in the early

days. At that time the stretch reflex and the spring model,

although known, were not in the vocabulary of coaches. In

explaining and promoting plyometrics, I and soon others talked much

about these concepts which were applied with great success by the

Soviets mainly through the works of Verkhoshansky.

Thus if any one purports to be very knowledgeable in this area they

should know about and be familiar with the works of Verkhoshansky.

They would have a much better understanding of how these concepts

are applied and very importantly, would understand why I have

criticised some of the conclusions by Weyand and others. I must

also once again remind you and others that I never challenged the

findings of his study. I did and still do challenge the conclusions

and the appications, which have still not been made clear.

General factors such as not doing limb speed work and ignoring

technique were brought out but what the training entails is still a

mystery. Can you enlighten us?

~~~~~~~~~~~~~~~~~~~~~~

Yessis, Ph.D

President, Sports Training, Inc.

www.dryessis.com

PO Box 460429

Escondido, CA 92046

~~~~~~~~~~~~~~~~~~~

[Guest guest]

Dr. Yessis wrote:

> [snip] I never challenged the

> findings of his study. I did and still do challenge the [snip]

> appications, which have still not been made clear.

>

> General factors such as not doing limb speed work and ignoring

> technique were brought out but what the training entails is still a

> mystery. Can you enlighten us?

Perhaps it would help if someone from outside the two camps, like me,

jumped in here.

Assuming, only for the sake of argument, that Weyand's research shows

that working on limb speed and technique don't improve running

performance, then the elimination of those types of training is

itself a practical application of Weyand's research.

The practicality of it is simple: it allows athletes to either spend

more time performing more effective training, or more time recovering

from training.

The Weyand camp need show nothing more than that to satisfy Dr.

Yessis's challenge to them to show a practical application of

Weyand's research. This issue should be considered well settled by

both sides.

Regards,

s

Ardmore, PA

[Guest guest]

> Once I hear back from you I will address the first point raised.

***

Hello Dr Yessis, yes this is acceptable and exactly what I would

like. So no emotional argumenting, only facts, asking for

clarification, showing research findings which contradict/support the

points raised. And last of all stick to the points raised. Let's go

to them one by one.

I will place the first one underneath:

Yessis (28/10):

1) First, since limb speed TIME, is basically the same between

fast and slow runners, why do you say that SPEED of movement is not

important? Does not the faster runner cover more ground? If time

is the same, speed of movement must be faster to complete the same

limb movement. It appears to me this is simple physics.

Put another way, if one runner has a stride length of nine feet, and

another six feet, can limb speed be the same for both runners?

Ross(30/10): yes, if ground contact time is shorter.

Yessis (9/11): Speed of the body is dependant on limb speed and

the push-off. (Limb) Speed (more accurately velocity) equals distance

divided by time.

Ross (11/11): (referring to the Weyand study): speed increase was

derived

from increasing stride length at lower speeds and stride frequency at

higher speeds. Stride frequencies at higher speeds came from shorter

ground contact time and shorter swing time (time a given foot was not

on the ground). In fact measurements showed that swing times for

runners of varying speeds are similar.

Question to Dr Yessis: you state the faster runner covers more ground

and thus have higher limb speed. Is this distance component during

ground contact only or during (ground contact + air time)? Can limb

speed be the same if ground contact time is shorter and (therefore)

distance covered during ground contact is the same?

Many thanks in advance for your response

Best Regards,

Stefan IJmker

Haarlem, The Netherlands

[Guest guest]

>if time of executiong the limb

> movements is basically the same, but one runmner covers greater

> distance with his limbs, can speed of limb movement be the same?

Stefan's response

In the example you stated, limb movement would be faster for the

person covering greater distance with his limbs.

This brings me to a question though: what does the above mean for

sprinting/fast running? And possible for (technigue) training? My

ideas are getting more and more clouded.

In my opinion Weyand also states something relevant to this issue. In

my opinion greater distance traveled by the limbs should be

accompanied by greater distance covered during ground contact (please

correct me If I am wrong in your opinion):

We found little difference in the third mechanism

that would enable faster runners to reach faster top

speeds: increasing the forward distance traveled during

the stance period or contact lengths. Our regression

equation indicated that contact lengths were 1.10

times greater for a runner with a top speed of 11.1 vs.

6.2 m/s. However, this resulted from a gender difference

in top speed: our female subjects generally had

shorter legs, shorter contact lengths, and slower top

speeds. Within groups of male and female runners,

contact lengths varied little or not at all in relation to

top speed. Although elongated steps would provide a

speed advantage by increasing the time available to

apply ground force, runners do not exercise this option

because unnaturally long steps compromise the ability

of the active muscles to apply the ground force necessary

to elevate the body for the ensuing step. By worsening

the mechanical advantage and disrupting the

natural spring-like behavior of the leg (8), unnaturally

elongated steps increase the muscle forces and volumes

that must be recruited per unit of force applied to the

ground (22). Reductions in the ground force applied in

relation to the muscle forces generated would directly

reduce maximum ground forces and therefore also reduce

top running speeds.

> Stefan

>

> Were you able to get the data that I requested regarding ground

> forces during the support phase?

>

Mr Yessis: to my knowledge this info is in the pictures I uploaded,

see the files section (ground reaction force pictures), take the zip

files (the newer ones). Foot position is marked as well as upper body

position. It is qualitative data at best, but I have no better data

at the moment.

Please state which data you are missing (if any), then I can search

for them. In the literature very few data have been published on

pictures relating body angles and vertical ground reaction force

profile. Maybe ST readers can help if needed.

Looking forward to your reply, thanks for putting effort in

responding.

Regards,

Stefan IJmker

Haarlem, the Netherlands

[Guest guest]

>

> There is no doubt in my mind that this issue will not be resolved

> by examining the separate facts as presented especially if my simple

> question on limb speed is too complex.

>

> Instead I will look at the Weyand study and the drawn conclusions as

> a person who knows little about running but who knows science and

> has an inquiring mind.

***

Dr. Yessis,

I did not say your simple question was too complex, but rather that

it was not well phrased. I said this because it was not well phrased.

Despite that fact I gave you an answer. It is disingenous to say you did not get

an answer.

Every question you've asked and re-asked, we've not only answered, we

gave you citations to numerous studies that back up our answers.

The fact that you did not accept the answers does not mean we did not

give them and it does not mean those answers are wrong. You have to

prove they are wrong.

When asked for proof of your contentions, you've been either

unwilling or unable to provide any. If there is research, why are you not

presenting it along with citations of the researchers? Since you have professed

being a scientist, I expected you to drop a

ton of studies on our heads that would show the foolishness of our

contentions and the irrelevancy of the work of dozens of locomotion

scientists. After several weeks of not seeing a single shred of

evidence that backs up anything you say.

Scientists can, and do, approach research with a set of

presuppositions. However, if the research leads to a different

conclusion, they accept that fact. We've posted from several research

papers in which this was the case. An excellent example was

the reseach regarding the much greater influence of vertical forces

over horizontal forces that supprised the researchers. They accepted

a different finding than they supposed.

When this was presented to you, you chose to deny the findings, just

as you've denied much of Weyand and dozens of other scientists.

You've made it clear that if research doesn't fit your

presupposition, then either the researchers or the research must have

been flawed.

By now, it's clear to me that you will not back up what you believe

to be important, running technique and horizontal forces in running,

because you can't back them up. I'm not speaking for those who read

or post here, but until you can provide proof of what you say and

teach, I personally see no relevance to your viewpoint on the issue

of running.

Barry Ross

Los Angeles, CA

[Guest guest]

**** Hello Dr. Yessis, thanks for your reply. It seems to me that you

are having a hard time in keeping one topic at a time. Well that's no

problem for me. I think I am also someone who knows science and has

an inquiring mind. So let's go through some or your remarks and see

if we can get a fruitful continuation of this discussion.

You (point 1 30/11):

> 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?

Me: Do you think repositioning of the leg is a volitional movement?

Tom Tellez for example said it was a passive movement: ground reaction

force and " recoil " provide the movement. What is the proof/ line of

thinking it is volitional, concentric muscle action.

Another question: if you do nothing in the air, where would the foot

land? Is it necessary to reposition the legs volitionally?

You (point 2 30/11)

> In regard to conctact length why is the distance traveled during

> contact so important? Is this the only time that the body moves

> forward or is pushed forward (even though it is stated there are no

> forces at push off)

Me

I am not sure whether I understand your argument. I guess it is

related to your idea that limb speed is important. However, during

contact the limbs are moved through an angle (for example hip

extension). If the legs are repositioned (toe-off to toe down for the

same leg) in the same time for faster and slower runners, as the

Weyand study indicated, Faster limb speed for the faster runner can

only mean that the angle of deviation was larger at toe-off, or that

more hip flexion occured during the front part of the swing.

I have not seen (kinematical data) to support the above faster limb

speeds for faster runners). What do happens, to my opinion, is that

the same angle (hip extension for example) is made during ground

contact by faster runners, in less time. So for ground contact there

is faster limb speed. However, the critical question is (and there is

the real discussion)about causality : does the limb speed provide the

speed of the runner or does the speed of the runner cause the

observed limb speeds.

You (point 3, 30/11)

> 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?

> 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.

Me: Could you provide a study / logical proof that backs up your

opinion that

" Don't the legs create a forward force when driven forward with great

acceleration? "

could you provide us the spring-mass studies which show the

importance of the arm and leg actions. This would help the discussion

I think.

Regarding arm movement in running it seems to be for balance (see the

research by Mann, 1983 and Hinrichs, 1992 (in book by P. Cavanagh)).

You point 4 30/11

> 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 foreces were greater than horizontal.

> This is understandable. But how can vertical forces propel the body

> forward? 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.

Me: If I am right Barry did not say that ankle extension did not

occur. Barry contended that it was a passive release of elastic

energy. You seem to say that ankle extension has a volitional,

concentric muscle effort. Let's look at research: Novacheck, 1998

shows in figure 4 (based on Mann and Hagy, 1980) that there is no

muscle activity of the gastrocnemius and the other muscles at toe-

off. However, Mero et al (1992,figure 2) do seem to show

gastrocnemius activity at toe-off. Who is right?

You point 5 30/11

Were calculations done to

> measure the force produced by gravity? 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 bodyweight force.

Me: I would like to see the calculation and the assumptions. Could

You (Dr Yessis) and Barry provide the calculations?

You point 6 30/11

> 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?

> But how can this be when no to very little movement in the leg

> joints takes place during the latter half of the contact phase?

Me: What is your take on this, Mr Yessis? How can we explain this?

You point 6 30/11

> 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. 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?

Me: is it possible that at take-off there is no/minimal force applied

by the leg to the ground: It may happen way sooner. The ground

reaction force data (see the files section) seem to indicate this.

The spring model does take into account the horizontal forces.

However at constant speed braking force = propulsion force. Net force

would be zero, regardless of the speed of the runner.

P1998, weyand Study:

" Because the net horizontal forces our subjects

exerted during each stride could not explain differences

in the top speeds attained, they were not included in our

analysis. "

Dr Yessis, what is your opinion about the importance of horizontal

forces at constant speed running? I will give an example: for an

elite sprinter braking forces will be minimal. Therefore propulsive

forces also have to be minimal. What is the need for accentuation of

horizontal forces?

Again, many thanks for your response.

Best Regards,

Stefan IJmker

Haarlem, the Netherlands

[Guest guest]

I thought my last post was going to be my last but I will submit

one more short final post.

I used the term complex because it was the only way I could figure

out why you could not answer yes or no to a simple question, So I

will ask it differently. If limb repositioning time is the same but

one runners limbs cover 3 more feet distance is his limb speed

greater?

I agree with you that vertical forces on most important ON TOUCHDOWN.

If they are most important in propelling the body forward, assuming

that running is a mostly horizontal, how do these vertical forces

move you forward?

You want me to provide studies but they would be wasted as there are

no substantiated conclusions presented. You have not backed up your

case with to -the -point answers. You answered only with facts that

relate to the topic not explain.

~~~~~~~~~~~~~~~~~~~~~~

Yessis, Ph.D

President, Sports Training, Inc.

www.dryessis.com

PO Box 460429

Escondido, CA 92046

~~~~~~~~~~~~~~~~~~~

****************

> >

> > There is no doubt in my mind that this issue will not be

resolved

> > by examining the separate facts as presented especially if my

simple

> > question on limb speed is too complex.

> >

> > Instead I will look at the Weyand study and the drawn

conclusions as

> > a person who knows little about running but who knows science

and

> > has an inquiring mind.

>

> ***

> Dr. Yessis,

> I did not say your simple question was too complex, but rather that

> it was not well phrased. I said this because it was not well

phrased.

> Despite that fact I gave you an answer. It is disingenous to say

you did not get an answer.

>

> Every question you've asked and re-asked, we've not only answered,

we

> gave you citations to numerous studies that back up our answers.

> The fact that you did not accept the answers does not mean we did

not

> give them and it does not mean those answers are wrong. You have to

> prove they are wrong.

>

> When asked for proof of your contentions, you've been either

> unwilling or unable to provide any. If there is research, why are

you not presenting it along with citations of the researchers?

Since you have professed being a scientist, I expected you to drop a

> ton of studies on our heads that would show the foolishness of our

> contentions and the irrelevancy of the work of dozens of locomotion

> scientists. After several weeks of not seeing a single shred of

> evidence that backs up anything you say.

>

> Scientists can, and do, approach research with a set of

> presuppositions. However, if the research leads to a different

> conclusion, they accept that fact. We've posted from several

research

> papers in which this was the case. An excellent example was

> the reseach regarding the much greater influence of vertical forces

> over horizontal forces that supprised the researchers. They

accepted

> a different finding than they supposed.

>

> When this was presented to you, you chose to deny the findings,

just

> as you've denied much of Weyand and dozens of other scientists.

> You've made it clear that if research doesn't fit your

> presupposition, then either the researchers or the research must

have

> been flawed.

>

> By now, it's clear to me that you will not back up what you believe

> to be important, running technique and horizontal forces in

running,

> because you can't back them up. I'm not speaking for those who read

> or post here, but until you can provide proof of what you say and

> teach, I personally see no relevance to your viewpoint on the issue

> of running.

>

> Barry Ross

> Los Angeles, CA

>

[Guest guest]

In regard to passive and volitional movements you have to understand

that in the passive action tremendous forces are generated and

dislayed. This is why I do not use passive as it infers something

not requiring great dynamic forces.

You also have to understand technique to understand how and when the

limbs are used. When learning, most of the actions are volitional

or a combo of volitional and " passive " which I will refer to as

automatic or learned actions. Runners who exhibit good technique

have learned the leg and arm actions well. When they run the

actions are automatic, i.e., involve no thinking.

When runners do not execute the actions well, as for example the

pawback action , it has to be learned. It will not be an automatic

action. This is but one example why technique is so important and

why it must constantly be adjusted as the runner further increases

his physical abilities.

Do the leges create a force? Stand in front of a runner and have

him drive the thigh into you. Now ask if this is a force

Regarding ankle exention it was stated that it did not apply a force

and was unimportant. If no force is exerted at this time (nor in

the leg actions) where is force for horizontal movement generated?

This is the crux of this discussion.

~~~~~~~~~~~~~~~~~~~~~~

Yessis, Ph.D

President, Sports Training, Inc.

www.dryessis.com

PO Box 460429

Escondido, CA 92046

~~~~~~~~~~~~~~~~~~~

************

>

> **** Hello Dr. Yessis, thanks for your reply. It seems to me that

you

> are having a hard time in keeping one topic at a time. Well that's

no

> problem for me. I think I am also someone who knows science and has

> an inquiring mind. So let's go through some or your remarks and see

> if we can get a fruitful continuation of this discussion.

>

> You (point 1 30/11):

>

> > 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?

>

> Me: Do you think repositioning of the leg is a volitional movement?

> Tom Tellez for example said it was a passive movement: ground

reaction

> force and " recoil " provide the movement. What is the proof/ line of

> thinking it is volitional, concentric muscle action.

> Another question: if you do nothing in the air, where would the

foot

> land? Is it necessary to reposition the legs volitionally?

>

>

> You (point 2 30/11)

> > In regard to conctact length why is the distance traveled during

> > contact so important? Is this the only time that the body moves

> > forward or is pushed forward (even though it is stated there are

no

> > forces at push off)

>

> Me

> I am not sure whether I understand your argument. I guess it is

> related to your idea that limb speed is important. However, during

> contact the limbs are moved through an angle (for example hip

> extension). If the legs are repositioned (toe-off to toe down for

the

> same leg) in the same time for faster and slower runners, as the

> Weyand study indicated, Faster limb speed for the faster runner can

> only mean that the angle of deviation was larger at toe-off, or

that

> more hip flexion occured during the front part of the swing.

> I have not seen (kinematical data) to support the above faster limb

> speeds for faster runners). What do happens, to my opinion, is that

> the same angle (hip extension for example) is made during ground

> contact by faster runners, in less time. So for ground contact

there

> is faster limb speed. However, the critical question is (and there

is

> the real discussion)about causality : does the limb speed provide

the

> speed of the runner or does the speed of the runner cause the

> observed limb speeds.

>

> You (point 3, 30/11)

> > 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?

> > 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.

>

> Me: Could you provide a study / logical proof that backs up your

> opinion that

> " Don't the legs create a forward force when driven forward with

great

> acceleration? "

>

> could you provide us the spring-mass studies which show the

> importance of the arm and leg actions. This would help the

discussion

> I think.

> Regarding arm movement in running it seems to be for balance (see

the

> research by Mann, 1983 and Hinrichs, 1992 (in book by P.

Cavanagh)).

>

> You point 4 30/11

>

> > 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 foreces were greater than horizontal.

> > This is understandable. But how can vertical forces propel the

body

> > forward? 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.

>

> Me: If I am right Barry did not say that ankle extension did not

> occur. Barry contended that it was a passive release of elastic

> energy. You seem to say that ankle extension has a volitional,

> concentric muscle effort. Let's look at research: Novacheck, 1998

> shows in figure 4 (based on Mann and Hagy, 1980) that there is no

> muscle activity of the gastrocnemius and the other muscles at toe-

> off. However, Mero et al (1992,figure 2) do seem to show

> gastrocnemius activity at toe-off. Who is right?

>

>

> You point 5 30/11

> Were calculations done to

> > measure the force produced by gravity? 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 bodyweight force.

>

> Me: I would like to see the calculation and the assumptions. Could

> You (Dr Yessis) and Barry provide the calculations?

>

> You point 6 30/11

> > 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?

> > But how can this be when no to very little movement in the leg

> > joints takes place during the latter half of the contact phase?

>

> Me: What is your take on this, Mr Yessis? How can we explain this?

>

>

> You point 6 30/11

> > 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. 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?

>

> Me: is it possible that at take-off there is no/minimal force

applied

> by the leg to the ground: It may happen way sooner. The ground

> reaction force data (see the files section) seem to indicate this.

> The spring model does take into account the horizontal forces.

> However at constant speed braking force = propulsion force. Net

force

> would be zero, regardless of the speed of the runner.

> P1998, weyand Study:

> " Because the net horizontal forces our subjects

> exerted during each stride could not explain differences

> in the top speeds attained, they were not included in our

> analysis. "

> Dr Yessis, what is your opinion about the importance of horizontal

> forces at constant speed running? I will give an example: for an

> elite sprinter braking forces will be minimal. Therefore propulsive

> forces also have to be minimal. What is the need for accentuation

of

> horizontal forces?

>

> Again, many thanks for your response.

>

> Best Regards,

>

> Stefan IJmker

> Haarlem, the Netherlands

>

[Guest guest]

" I used the term complex because it was the only way I could figure

out why you could not answer yes or no to a simple question, So I

will ask it differently. If limb repositioning time is the same but

one runners limbs cover 3 more feet distance is his limb speed

greater? "

Already answered several times.

" You want me to provide studies but they would be wasted as there are

no substantiated conclusions presented. "

My response to this is the same as my last post to you:

" By now, it's clear to me that you will not back up what you believe

to be important, running technique and horizontal forces in running,

because you can't back them up. I'm not speaking for those who read

or post here, but until you can provide proof of what you say and

teach, I personally see no relevance to your viewpoint on the issue

of running. "

Barry Ross

Los Angeles, CA