Significance of Force Application in Max Velocity Sprinting, Part 11

We are back with the series on Force, Ground Contact and Sprinting, and once again, we have Kenta’ Bell again.

To review:

Significance of Force Application in Max Velocity Sprinting

Part One: Foot and Ankle Usage

This article was written by Kenta’ Bell, a two time Olympian (2004, 2008) in the Triple Jump and the 2001 Gold medalist at the World Student Games in Beijing, China.  His PR is an impressive 17.63m (#9 on the all-time USA list) and he is also the 2003 & 2010 USA National Champion.  Visit his website www.thinkingfeet.com or you can contact him directly at yourthinkingfeet@gmail.com

This is the first in a series of articles that I will be writing on force production as related to sprinting and running in general. I have been somewhat apprehensive about beginning this series due to the nature of how many so-called sprint gurus already exist. However, frustrated by reading countless articles based on pseudo-science and blatant lies based on the figment of somebody’s imagination along with the compulsion to be different has left me no other choice. When it comes to force production as related to sprinting everybody says you need more of it, but offer little to no input into how to effectively and efficiently create it. Many of you are asking yourselves right now how does a former triple jumper knows anything about sprinting mechanics and force application?

Simple!!!

We, being jumpers do in 20m what Usain Bolt does 70m. When competing, I often reached velocities well over 11meters per second in the final 10m of my approach run. My preferred and most successful run throughout my career was only 98ft or 29.8m in length. What you have to understand is that not only does the elite jumper have much less time create these velocities, but in the case of the triple jumper has to continue to summate the forces three additional. This being done while at world-class sprint velocity. What I am going to share with you is not something that I heard 20 years ago and decided to put my own spin on. This data has been long developed and tested throughout my professional career.

Most notably in the Locomotor Performance Laboratory of Dr. Peter Weyand on the campus of Southern Methodist University. In our studies we used high-speed treadmill and force platforms to analyze ground force, vertical ground forces, and contact times. Most significantly, we were able to identify the areas of the foot that produces the highest vertical forces. In the first of this series I will be decoding sprint force development from the ground up. I will explain how to prepare the body stabilize and create huge amounts of voluntary forces.

The most important factor in determining sprint performance is the ability to quickly apply force to the ground. Previous research has shown that faster runners can apply greater amounts of force down into the ground during briefer Ground Contact phases than slower runners. This high rate of vertical force application leads to shorter Ground Contact times as well as longer Stride Lengths, thus allowing these faster runners to attain greater maximum speeds. Elite sprinters often apply peak vertical forces of 3-5 times body weight and average vertical forces of 2-2.5 times body weight during each Ground Contact.

Coaches have long debated the best way to achieve higher sprint speeds throughout time. During one particular period everyone looked at stride length as the most important contributing factor. That era was ushered out and in came the era of frequency and fast leg mechanics.

What I am going to show you is that the simplest way to improve overall speed is by improving vertical ground force. This enhancement not only increases maximum stride length, but stride frequency as well. If you took an athlete who has been amputated on both legs from the knee’s down and amputated at the arms from the shoulder down how would you make him faster? It’s going to be hard to improve stride length without the use of the lower leg. Likewise, it’s going to be extremely difficult to generate negative foot strike through front-side mechanics. The sole and independent way to this is by improving his/her ability to generate higher vertical ground forces.

The first and most important area to look at is foot strike, or as I like to refer foot plant. How and where we place our foot is the most important aspect of speed and human locomotion. You can build as big of an engine as you would like, but all of that force has to be transferred to the track through the foot. Contrary to tradition dorsi-flexion and landing on the ball of the foot or toes yields no necessary advantage when it comes to running fast. Ironically these two things can be far more detrimental than beneficial to your overall performance. We will evaluate the role of the foot and ankle in the following order:

  1. Foot Strike: ball of foot vs. flat foot landing
  2. Reactive properties of the arch
  3. Dorsi-flexion vs flat/neutral
  4. Achilles and the gastorc/soleus region

1) Ball of the foot vs. Flat foot strike

We walk flat footed; or heel- to- toe to be specific. We jog flat-footed and in most cases do striders with a flat foot landing. We wouldn’t dare go into the weight room and perform a squat or any Olympic Lift on the balls of our feet. However, throughout the majority of my lifespan I was always told to get on the balls of my feet when I sprint. We have identified in the weight room that staying flat gives us better support and balance. Likewise, we have identified that driving down through the heel and engaging the hips and gluteus muscle group is the best way to generate high forces and achieve maximum power output. Thus the action of landing towards the back part of the heel can best be termed as bridging the foot. This act of transferring angular momentum and conserving energy expenditure as we cross the from front to back of the foot is not only superior, but biomechanically sound in its principle.

Most of you are wiling to debate and argue that landing flat-footed will be significantly slower and you will spend too much time on the ground. Both of which are negative. Landing flat-foot in sprinting significantly reduces ground contact time while improving vertical ground force, which I will explain in detail later. The act of landing flat can be best looked at as [load/unload] eccentric/concentric voluntary reactions. In sprinting or running on the balls of the feet the action occurs in the series of [land/collapse/load/unload]. In layman’s terms it’s the difference between having one in the chamber as opposed to cocking the hammer to load one before pulling the trigger.

Force reduction and production in the triple jump

Above: Structures the load/unload paradigm of human performance. Specifically in athletic events where power and force are the optimal components.

clip_image004

Above: Translates peak vertical where related to foot contact and force application

2) Reactive Properties of the Arch

A major advantage to flat flatter foot placement is found in the elastic material in the arches of the feet. Many ignore the huge amounts of performance enhancement that can be gained by 1) placing the foot in the appropriate position to load this elastic material and 2) having properly developed the elastic connective tissue that runs along the arch and plantar fascia of the foot. The following article best describes the phenomenon of the human foot at work.

“The extremely rapid development of ground force.  Typically, peak ground forces of ~600 pounds are generated in less than one-tenth of a second at sprint racing speeds. The forces on the arches of the feet and Achilles tendons are appreciably greater than the 600 lbs sprinters slap onto the track. Without the necessary muscle-tendon force production and transmission from the legs and feet to the ground, there is no speed. Since the amount of muscle (and active muscle force) that can be packed into the arch is limited by its small size, the foot manages to generate the huge forces largely passively. This is accomplished with the ligaments that span the arch (the plantar fascia and deeper layers of springy material that connect the bottom of the heel to the ball of the foot). The benefits of the passive force from the ligaments springs are two:

  1. huge forces can be developed with very little material, and
  2. there is essentially no limit on how quickly the force can be generated.

Connective tissue, unlike muscle, has no lag time for activation – the arch ligaments develop large forces as quickly as the body’s weight loads them by flattening the arch. So, generating > 600 lbs in less than a tenth of a second is no problem. In fact, tendons and ligaments function better elastically when they are loaded and allowed to recoil quickly. The trick is to have the right amount of material (ligament dimensions) for optimizing elasticity without breaking.” (Ker, R.F. et al. (1987) The spring in the arch of the human foot. Nature, 325: 147-149.)

3) Dorsi-Flexion vs. Neutral Stance

I have long felt that we have abused and misused the term as a whole. Sometimes it’s the go to catch phrase for coaches when they don’t know what else to say. My personal take is plain and simple. When you stand you are neither dorsi-flexed nor plantar flexed with the foot/ankle joint. At this position a neutral ankle is supporting you. If you lean forward to the optimal sprinting position from the ankles and not the waist you are now appropriately dorsi-flexed and elastically loaded in the Achilles Heel tendon. The particular position of forward lean I am describing will be best achieved when the breastbone is directly over the toes. If you were to take a measurement of this angle you would find it to be somewhere between fourteen and eighteen degrees of flexion. Unfortunately, an excessively tight Achilles tendon from attempting to remain dorsi-flexed has limited the appropriate range of motion in the majority of athletes. Coupled with structural abnormalities of misaligned talus and calcaneus has greater exasperated the malfunctions dorsi-flexion.

4) Achilles & The Gastroc/Soleus Region

Having now planted the foot flat in the correct neutral position which by way of correct body lean is now flexed and loaded. This pre-activates the stretch inhibitors of the Achilles, along with the spring like tissue of the Arch will now voluntarily produce large amounts of force in very little coupling time. This force not only comes from the foot and ankle, but the calf muscle group as well.

In short, by understanding the some very simple concepts of stretch reflex along with common sense biomechanical principle the coach and athlete can now transfer and generate greater forces and reduce ground contact time. This means more time sprinting and less time wasted on the ground. One has to understand that sprinting happens above the ground. This only happens when the principles of vertical force application are present. By effectively understanding and learning how to correctly use the foot and ankle joint the sprinter can thus begin to improve his/her vertical ground forces and overall speed.

Now that the athlete comprehends the concept he/she needs to build and develop the appropriate stretch/reflex and spring like material in the foot and ankle joint. I have personally found the jump rope to be one of the best tools for developing the necessary strength, speed, muscle endurance, and neuro-muscular coordination for athletes. I have achieved the best results in myself and many others when rope skipping was performed bare feet without the usage of shoes. This allows the toes spread and the elastic material of the arch and Achilles heel to be properly strengthened. One has to remember that jump roping and skipping are considered the first two forms of plyometrics.

I would also encourage the coach and athlete to stray away from calf raises and spend more time addressing the negative stretch aspect of the calf extension exercise. This means allowing the heels to drop or lower as far as possible before returning to a neutral position. This eccentric or negative strength training will yield huge benefits in range of motion and elastic response.

In part to 2 will be discussing the role of using the hips and Gluteus muscles in sprint Force Development.

Also stay tuned to my website www.thinkingfeet.com where I will soon be releasing a great video on plyometrics, bounding, and strength training for distance and middle distance runners.

Comments

  1. Fabien says

    Really great article. It’s almost impossible to find a good reference on amortization and foot contact. Most people are all about propulsion and don’t really care about amortization and proper foot contact. Now I have a question. I always felt that good posture + good recovery mechanics+ foot contact awareness using little hoping as mentionned was all it takes to have a good foot strike, usually while those elements are in place the body is smart enough to take care of every thing else. Do you agree with me or do you have more to say about it?

    • Jimson Lee says

      @Fabien, I can’t speak for Kenta’ Bell (he wrote the article) but I feel proprioception plays a huge role.. in fact, it was supposed to be my Masters thesis back in 1987!

    • Kenta' Bell says

      Fabien, you are exactly correct most people are over consumed with the propulsion side of running and jumping. most teach vertical jumping, box hops, and hurdle hops on the propulsion side. Proper foot contact sets up the whole recovery cyclic motion to become voluntary by way of stretch reflex. In all respect I know that at top speed the foot doesn’t actually land flat. The optimal position at max velocity is at the back/last row of spikes on the spike plate. I just find that most athletes are so consumed with dorsi-flexion that they are actually stabbing/stubbing the ground. Or they get so locked into dorsi-flexion the never release the ankle to push off into triple extension. I look at training like a pendulum swinging. Most coaches/athletes are too far on the front of the pendulum swing. Therefore, I look to shift training and preparations back the other way in an attempt to find the happy medium. The last thing I want to do is create more drills and exercises. I’m always looking to establish self teaching and self correcting systems. The end result is to get more force and propulsive power on toe-off. In the gym I look for triple extension on pulls, squats, and etc…. understanding that is the finishing and not starting position.

  2. says

    Great article, Kenta. I see in your comments you mention contact with the back of the spike plate…so not exactly flat footed. Which begs the question on heal strike. In a “back of spike plate” contact is heal contact needed, important, destructive…?

    I’ve been playing with heal contact and I’ve had some good times (using Freelap) in flying 30s. I was focusing on thrusting my “back of spike plate” (didn’t use that term, but it works) into the ground and then letting my heal strike afterwards. I played with “back of spike plate” without heal strike, too. Both were improvements over my previous cues, but I didn’t see a clear winner between the two. I also looked at slow motion of several elite 100m runners to see how close their heals were to the ground. It seems “most” get very close but do not come in contact.

    Anyway, do you have any results with Weyand about heal strike?

    • Fabien says

      the heal should flirt the ground either touching very slightly or letting a very thin space between the heel and the ground. What really matters is the loading of the achilles tendon unit by use of an optimal yielding. if you’re touching the ground too much you will not have anymore loading of the tendon and ligaments and it will be detrimental, if you don’t yield enough the springs will not be optimally loaded and you will loose some elastic energy that are there for free. Now to work on that my feeling is that if you work hoping and bounding in different kind of enviroment (different ground contact time, different tension, surfaces,…) the body will naturally find the good equilibrium provided that the technique is good. just my 2 cents.

  3. says

    I teach foot position base on pelvic tilt position , so yes posture plays a big roll. But at the same time if the feet are allowed to move freely, that includes toes, arches and all the joints then the pelvic tilt switches to what is best.
    You have one problem shoes that roll you from heel to toe and even from ball of foot to toe so that kills the amortization phase. So the next best option is control your pelvic tilt to influence amortization.

  4. Eric Broadbent says

    “Landing flat-foot in sprinting significantly reduces ground contact time while improving vertical ground force, which I will explain in detail later.”
    I have to disagree with this…and I think all elite sprinters would as well. See video: http://www.youtube.com/watch?v=4QrlPmK4B94. No one is running flat footed here.

  5. Eric Broadbent says

    While I don’t think sprinters are entirely up on the ball of the foot, I would never call the landing flat footed. I think if we told an athlete that then we wouldn’t see anything desirable. Even the majority of elite distance runners have foot contacts more similar to that of a sprinter and you won’t see a “flat-footed” contact.

  6. Fabien says

    Because of the extension of the hip and knee, the ankle will have a tendency to extend naturally too much with some people (we all have this terrible picture of people hoping with there toes pointing towards the floor) and they will land on the ball of the foot (or too much in the front part of the foot if you prefer) causing a breaking effect leading in particular to chronicle shin splints. People tend to cue fully dorsiflexed ankle. While this can be a good cue in some particular instances I think cueing flat foot landing is a better coaching approach in most cases. If you insist too much on the dorsiflexion you’ll have cocontraction of agonist antagonist and start to see weird things.

    In actuality while cueing flat foot landing, as explained in Kenta’s comment, what happens is that you land the part of the foot that corresponds to a little more than the ball of the foot and then there’s a yield that is synchronized with the yield of the hip and knee. And then you’re almost litterally almost flat footed. The all idea of this thing is that you don’t want to be too much dorsiflexed as it is unatural to the triple extension and will not provid a proper amortization but you don’t want too much extension of the ankle too avoid breaking and to put your foot into a position that can not provide a synchronized yielding with the hip and knee. Yielding is key and everything has to be in harmony. Again cueing dorsiflexion or flat foot contact is not bad what matters what matter is why you cue this and that and how a particular athlete react to it.

  7. Eric Broadbent says

    Great explanation I just think that what we are cueing vs what we are seeing are two entirely different things.

  8. Slow old bloke who likes sprinting says

    I read the article a couple of days ago and have to say it is one of the most informative and thought suggesting articles I have read for a while, maybe at all. I am a masters athlete but am equally interested in the science / biology behind improving speed and sprinting.

    There are so many articles out there suggesting that technique is the best way to achieve this and running on the forefoot seems to be the only way advocated.

    I know this, every athlete is different, some have a natural tendancy towards speed of movement, others brute strength and others endurance, and we will all react differently to different training and different running styles. However, and i’m sure I can’t be alone in my observations, when I hop using the whole of my foot including driving off of the heel I cover a much larger distance than just using the forefoot. My observations of triple and long jumpers is that the take off and landing phases of the jumps are always done using the whole of the foot. I am not an expert but my experience is that when using the whole of your foot, it is much easier to generate more power. I agree that there may be some sacrifice with the snappiness you feel and some may argue that stride frequency may reduce, but I cannot measure this and am open to Kenta’s suggestions that the opposite is actually the case.

    Anyway, the point of my post is that I thought I have to give this a try and experiment between running on the forefoot only, compared to using the whole of the foot. When using the whole of my foot I found the most natural movement was to allow the forefoot to strike very fractionally before the heel, but in a neutral flat position, allowing some control, but for the heel to then make contact and to then drive forward and upwards fully off the whole foot, as if hopping.

    I was running 6 x 150 (5′) and I alternated between the two techniques. Every run I did using the whole foot to drive was 0.7 seconds quicker than using the forefoot! My belief at the outset was that using the heel could not possibly be quicker, because of everything I have been led to believe. Now I am left with the only conclusion that for me, the amount of power developed on each foot strike is much more important than anything else in determining running speed.

    It seems very difficult to argue that running using the whole of your foot is better, when none of todays elite sprinters do it. Yet to my knowledge all of todays elite jumpers do jump using the whole of the foot. An interesting debate…

    I think it is up to everyone to find the technique that suits them the best, based on their natural tendancies, but if Kenta is doubting whether he should impart his athletic knowledge to the rest of the world, I would urge him to share it.

  9. says

    @Slow old — the foot strike debate here is really only valid for Maximum Velocity sprinting. Once you get to longer distances, the form changes. Many elites at 400m start landing flat footed (maybe even very, very slightly heal first). Look at Karani James 400m final in London. I’d have to venture that your workout — 6×150 (?) [5'] — is more akin to 400m form.

  10. Slow old says

    Interestingly I do train 200/400 rather than 60/100. My training yesterday happened to be 150′s so it is the only thing I have to base my comments on so far. What you say may be correct, and I have no way of providing accurate data to support my post, i’m just trying to logically apply why Kentas principles seem to work for me.

    I know this is a very simple analogy, but to me sprinting is basically a number of one legged jumps put together. Technique and finesse stops you wasting what you’ve got, but without power you’ve got nothing. You see all types of form in elite sprinting, good, bad and the different, but every single world class athlete has extreme levels of muscular power in common.

    A one legged broad jump is the single rep equivilant of sprinting, whereas 100m may actually be 40 or so reps. A broad jump like this is all about power. The distance jumped is a result of the take off velocity as you foot leaves the ground, which is a result of the acceleration you applied to the ground and the equal and opposite force the ground applies back to you. You cannot move forward faster than the horizontal element of the velocity of your centre of mass, as your foot leaves the ground. It is impossible as no more force can be exerted on to the ground. Your maximum sprinting speed is therefore directly limited by the horizontal element of this take of velocity, which is directly linked to the amount of power you can apply. I may have read some of Kenta’s article wrong, but this is where I really think he is on to something, applying the basic laws of physics.

    We all think of 100m as being pure speed but it cannot be. In the gym you would be lucky to get 60% of your maximum weight if you had to do 40 reps. The take of step of the long jump and jump phases of triple jump are much closer to a single rep max than the 100m sprint. Again I think Kenta’s arguement really stands up here as not many will be able to argue with his knowledge or experience of jumping.

    Thus, I think that if there is relevance for a jumper to use a flat foot for take off, when absolute maximum power is needed in one step, there has to be some validity in the possibilities crossing over to sprinting. I’m really interested in anyones thoughts as ultimately we all share the same goal, to get faster.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>