We are back with the series on Force, Ground Contact and Sprinting, and once again, we have Kenta’ Bell again.
- Part 1 Plyometrics, Ground Contact Time, and Sprinting was simply to demonstrate the faster the movement, the shorter the ground contact time.
- Part 2 covered How to Weight Train without Weights and it focused on speed strength.
- Part 3 was Driving Resistance Band Training with a video from Remi Korchemny.
- Part 4 discussed the 5 different types of “strength training”.
- Part 5 was a presentation by Tim Egerton on Explosive Strength Training [video broken]
- Part 6 was Dynamic Isometrics & Sprinting: Explosive Strength Training
- Part 7 , 8, 9 was Advanced Plyometrics for Jump and Sprint Training and Ballistic Power for Better Athletic Performance and a video on How to Teach Bounding written by Kenta’ Bell, a two time Olympian in the Triple Jump.
- Part 10 was Eccentric Strength with Bobsled coach & former UKA Sprint coach Stuart McMillan
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 firstname.lastname@example.org
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?
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:
- Foot Strike: ball of foot vs. flat foot landing
- Reactive properties of the arch
- Dorsi-flexion vs flat/neutral
- 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.
Above: Structures the load/unload paradigm of human performance. Specifically in athletic events where power and force are the optimal components.
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:
- huge forces can be developed with very little material, and
- 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.