Agility might be the most misunderstood concept in the performance field as our profession lacks a thorough understanding of its meaning and its application.

Over the past 40-years, agility has run through the musical chairs of definitions. Since the 70s, we’ve used phrases such as:

• Ability to change direction rapidly
• Ability to change direction rapidly and accurately
• A whole-body change of direction and speed

Currently, the most accepted definition today is:

“A rapid, whole-body change of direction and speed in response to a stimulus” - Sheppard & Young, 2006

But even this definition leaves a lot to be desired and misses the boat on a number of important pieces (which we’ll get into).

Strength and conditioning specialists will typically look at agility through the lens of physical abilities: strength qualities, eccentric/isometric qualities, and reactive strength.

Pair this with most S&C’s education involving a big piece on biomechanics and you’ll see a large influence on a mechanical and technical model of joint angles, specific body positioning, foot placement, and kinematic/kinetic data driving feedback.

You can see this biomechanical bias with the need for coaches to categorize and label movement into terms like crossover step, side-step, split-step, hip turn, directional step, power cut, etc. and then use these to build their “movement” library.

This is an exercise of futility and only works to water down and miss the complex nature of the athlete-environment relationship.

With this in mind, it’s imperative to remember that agility lives within a specific context, and without that context, there is no agility. So agility is NOT a singular bio-motor that one possesses or not, it depends on the context in which it’s being asked.

This is where the current definition of, “in response to a stimulus”, leaves a lot to be desired.

It’s not about a response to just any stimulus, rather it’s about the pick-up of specifying information from the athlete’s specific sporting environment to guide movement behavior.

I often think about the following quote when it comes to agility or better put, sport movement,

“Everyone is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

If we try to judge an athlete’s agility, outside of the context and environment in which they’ll be asked to perform, you’re not testing their agility.

Just as an NFL wide receiver may possess incredible agility on an NFL Sunday, place that same athlete on a soccer pitch and they’ll look like a fish trying to climb a tree.

Or if we ask an offensive lineman to play wide receiver their “agility” will clearly be lacking. BUT if you watched that offensive lineman all game, both in run blocking and pass protection, there is no doubt you’d come away saying they possess great agility to be able to pull out in front of their running back to kick out a linebacker, or to pass set on a speedy defensive end, or to handle a stunt with ease.

There is a reason athletes play and specialize in certain positions (offense vs defense) as they are better equipped to handle the information and tasks of each.

For instance, watch a basketball game, on one end of the court an athlete will look amazing as they blow by a defender for a dunk, then on the other end, they’ll struggle to stay in front of the player they just burned.

Hopefully, you can start to see how we must change the lens in which we view sport movement. If we truly think a 505 or L-Drill or star drill is capturing the essence of agility, you’ll be disappointed. 

To really capture this process, we need to appreciate the environment in which movement will organize and emerge. So going back, there is no singular definition or drill that can capture agility, it all depends on the task and performance environment.

So what does all this mean?

First, we have to respect the environment as much as we respect the athlete themselves. The athlete is always performing in an environment; the athlete and that environment are always linked and their relationship is mutual. So in my opinion agility has to start with an environment.

Second, that environment should seek to preserve the key specifying information variables from sport. To make agility stick and transfer to sport, coaches must ensure the information in their training activities is similar to what they’ll encounter in the game. 

So think about variables like space, time, opponent(s), equipment, rules, situations, and intentions of the game environment and see if you can maintain some essence of those in your training activities.

Lastly, as stated early, agility is not something that one possesses and owns; it’s an ongoing and continually adapting process. Athletes don’t actually acquire the skill of agility; rather athletes gain experience of adapting and picking-up specifying information (becoming more attuned) and then organizing and scaling movement solutions to this specifying information (calibration).

​With all this mind and with the framework of viewing agility not only through a movement pattern lens, but also an environmental/task lens.

For the few out there that actually follow our work at BBA and listen to our podcasts, you probably notice our theme... we are movement based.

We take a movement centric approach to training our athletes, which is backwards from the weight room centric approach most S&Cs take. We value the weight room, but it is only an accessory to our actual movement training. 

​With that being said, we try to base our movement training and subsequent learning process from an ecological, CLA, rep without rep standpoint rather than a perfect practice, mental model, rep after rep standpoint.

With this process has come the difficult task of communicating with coaches as the terminology used are not likely to be seen in college classes or in common coach interactions. This is sad because the literature is rich and deep in this area and very valuable for all coaches to be familiar with. Being on the same page, and understanding the basic terminology will help coaches have meaningful discussion on these topics. 

​Below are basic "definitions" of key terms that are common in movement discussions and will help put everybody on the same playing field. You will also find some important books to consider, numerous research articles to explore, podcasts that clearly layout and discuss these principles, and websites that contain great information. 

A big thanks to Tyler Yearby (@TylerYearby) for his help and contributions to this work. Many of the following are additions and inserts from his study, so the thoroughness of this list is in major part to him!

Have fun exploring this deep rabbit hole!

• Affordances: Opportunities for action. 

The environment offers “ability” of actions – the ball has catch-ability, the gap has jump-ability, the space has run-ability. Affordances are dynamic; they can change over short and long time scales based on changes in the environment, task, and organism.
 
Information in the environment is directly perceived, which contains affordances (opportunities for action). Information specifies affordances, those properties of the environment whose perceived meaning is the actions they both allow and invite and organism to perform (Araujo, D., & Davids, K., 2011).

• Constraints Led Approach: Framework to explain how coordination emerges under constraints (Individual, task, environment) that operate under differing time scales. (Newell, 1986)

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• Constraints:  Internal or external boundaries, limitations, or design features that restrict the number of possible configurations that the many degrees of freedom of a complex system can adapt. (Glazier, 2015. Towards a Grand Unified Theory of Sports Performance). Constraints can have spatial or temporal components or both, they reside at all levels of analysis from microscopic to macroscopic, and they operate over a multitude of different time scales, from milliseconds to years. Actions are not caused by constraints; rather, some actions are excluded by them. Typically we consider three types of constraints...

1. Task Constraints: Specific to the task being performed. They are related to the goal of the task and the rules governing the task. They are not physical, rather they are implied constraints or requirements which must be met within some tolerance range in order for the movement to produce a successful action. (Glazier, 2015. Towards a Grand Unified Theory of Sports Performance)
2. Individual (Organism) Constraints: Reside in the individual movement system including those of physically, physiologically, morphologically and psychologically. (Glazier, 2015. Towards a Grand Unified Theory of Sports Performance)  
3. Environmental Constraints: External to the movement system. They tend to be non-specific that pertain to the spatial and temporal layout of the surrounding world that continually act on the movement system ie playing surface, weather, ambient light, crowd noise, temperature. (Glazier, 2015. Towards a Grand Unified Theory of Sports Performance)

• Ecological Dynamics: Considers athletes and sports teams as complex adaptive systems and examines the emergence of sports performance at the level of the performer-environment relationship and is distinguished by constraints of each individual performer and physical characteristics of participation locations for athletes activities, but also by social and cultural factors surrounding performance. (Araujo, Davids & Hristovski, 2006)

Ecological Dynamics framework sustains a scientific approach to studying the behaviors of neurobiological systems, especially processes of action, perception and cognition (Ecological Dynamics: a theoretical framework for understanding sport performance, physical education and physical activity, Seifert, l. & Davids, K., 2016).

Kugler and Turvey [1] considered that "Ecological science….is a multidisciplinary approach to the study of living systems, their environments and the reciprocity that has evolved between the two (I also liked this from the same paper). 

• Ecological Psychology: A field of psychology where perception is the functional act of picking up information from the environment to use for regulating movement, NOT for enhancing its automaticity.

• Representative Environment: is a framework for assessing the degree to which experimental or practice tasks simulate key aspects of specific performance environments (i.e. competition). The key premise being that when practice replicates the performance environment, skills are more likely to transfer (Krause, Farrow, Reid, Buszard, Pinder, 2018)

• Dexterity: Ability to discover a motor solution for any external situation. Bernstein further stated that dexterity is demonstrated by the ability to solve a motor problem correctly, quickly, rationally, resourcefully. (Bernstein, Dexterity and it’s Development). Dexterity is not a property of the movements themselves, rather in the processes of the solutions ​

• Motor Control: How the nervous system interacts with other body parts and the environment to produce purposeful, coordinated movements. (Latash, 2012. The Bliss of Motor Abundance)

• Technique: Technique can be considered the kinematics used during a movement. BUT the study of kinematics alone does accurately describe HOW that technique emerged.

It is better to think of technique as the execution of a decision. Technique is linked to the information source, so it isn’t absolute or permanent; it varies depending on the context in which a movement is being asked. Technique is a result of individual, task and environmental constraints of a particular movement. Technique is the outcome of intention and perception, thus technique needs to be studied in that realm.

• Action Fidelity: The complete movement action (intention-perception-action) is an accurate (it looks, feels and acts) “picture” of sport.

• Non-Linear Pedagogy: A learner-centered approach to skill acquisition. An umbrella term for teaching and coaching that uses task and environment design to develop skill acquisition, where each learner will have individual periods and rates of learning.

• Repetition Without Repetition: The process of practice consists of the gradual success of a search for optimal motor solutions to the appropriate problems. Because of this, practice, when properly undertaken, does not consist in repeating the means of solution of a motor problem time after time, but in the process of solving this problem again and again by techniques which we changed and perfected from repetition to repetition. (Bernstein, 1967; The Co-ordination and Regulation of Movement) ​

• Differential Learning:​ Takes advantage of fluctuations in a complex system by increasing them through no two repetitions being the same by constantly changing movement tasks creating perturbations to the complex system.

• Decision-Making: Can be viewed as a functional and emergent process in which a selection is made among converging paths of actions for an intended goal (Araujo, Davids, Chow, Passos, Raab, 2009). Learning to make successful decisions is concerned with the education of intention, attunement, calibration and mastering perceptual-motor degrees of freedom.  ​

• Degrees of Freedom: There are multiple ways for humans to perform a movement in order to achieve the same goal. There is no simple, one-way, to perform a movement. Complex movements, involving a greater number of “moving parts” (joints, muscles) involve greater amounts of degrees of freedom.

• Contextual Interference: Memory and performance disruption that results from practicing multiple skills in the context of a practice session. In general, the contextual interference phenomenon of learning during practice = more interference during practice leads to better learning than less interference.

• Time Scales: Rates of change in motor learning

• Explicit Learning: Learner acquires skill and knowledge deliberately and consciously.

• Implicit Learning: Learner acquires skills and knowledge without conscious awareness.

• Dynamic Systems Theory: Non-Linear systems of highly inter-connected systems composed of many interacting parts, capable of constantly changing their state of organization.

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• Coordination:
• Bernstein said, “Coordination is overcoming excessive degrees of freedom of our movement organs, that is, turning the movement organs into controllable systems.”
• Gibson said, “Actions emergent in the temporary couplings formed among the individual and the environment.”
• Newell said, "Coordination can be viewed as the function that constrain the potentially free variables (DoF) of a system into a behavioral unit (movement solution)”​

Coordination is a property of the solution that emerges from each individuals movement system in response to the constraints the system is facing.

• Emergent Movement: Movement behavior or solution that results from the interaction of task, environment and individual constraints.  ​

• Self-Organization: Ability of a system to spontaneously organize itself into patterns of coordination. Specific stable patterns form through organization of the available DOF as coordinated movement during complex actions as a product of the constraints that are placed upon it. ​

• Degeneracy: Human movement system degeneracy is the ability of the athlete to effectively perform a movement in a variety of different ways through varying levels of complexity.  ​

• Effectivities: Capabilities of the individual  ​

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• Skill acquisition/adaptation: A functional performer-environment relationship (Araujo & Davids, 2011). Or a reciprocal functional relationship between and individual and the environment.

Research Articles:
 

• Araújo, D., & Davids, K. (2011). What exactly is acquired during skill acquisition?. Journal of Consciousness Studies,18(3-1), 7-23.

 

• Seifert, L., Button, C., & Davids, K. (2013). Key properties of expert movement systems in sport. Sports Medicine, 43(3), 167-178.

 

• Davids, K., Glazier, P., Araújo, D., & Bartlett, R. (2003). Movement systems as dynamical systems. Sports medicine,33(4), 245-260.​

  

• Glazier, P. S. (2017). Towards a grand unified theory of sports performance. Human movement science, 56, 139-156.

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• Bartlett, R., Wheat, J., & Robins, M. (2007). Is movement variability important for sports biomechanists?. Sports biomechanics, 6(2), 224-243.

 

• Latash, M. L. (2012). The bliss (not the problem) of motor abundance (not redundancy). Experimental brain research,217(1), 1-5.

 

• Glazier, P. S., & Davids, K. (2009). Constraints on the complete optimization of human motion. Sports Medicine,39(1), 15-28.

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• Strafford, B. W., Van Der Steen, P., Davids, K., & Stone, J. A. (2018). Parkour as a donor sport for athletic development in youth team sports: insights through an ecological dynamics lens. Sports medicine-open, 4(1), 21.

 

• Renshaw, I., Davids, K., Araújo, D., Lucas, A., Roberts, W. M., Newcombe, D. J., & Franks, B. (2018). Evaluating Weaknesses of “Cognitive-Perceptual Training” and “Brain Training” Methods in Sport: An Ecological Dynamics Critique.Frontiers in Psychology.

 

• Franks, B., Newcombe, D., Roberts, W. M., & Jakeman, J. (2017). Shhh… We're talking about the Quiet Eye! A Perceptual Approach to the Transfer of Skill: Quiet Eye as an Insight into Perception-Action Coupling in Elite Football.

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• van der Kamp, J., Dicks, M., Navia, J., & Noël, B. (2018). Goalkeeping in the soccer penalty kick: it is time we take affordance-based control seriously!. Sportwissenschaft, 48(2), 169-175.

 

• Teques, P., Araújo, D., Seifert, L., del Campo, V. L., & Davids, K. (2017). The resonant system: linking brain–body–environment in sport performance☆. In Progress in brain research (Vol. 234, pp. 33-52). Elsevier.

 

• Farrow, D., & Robertson, S. (2017). Development of a skill acquisition periodisation framework for high-performance sport. Sports Medicine, 47(6), 1043-1054.

 

• Spiteri, T., McIntyre, F., Specos, C., & Myszka, S. (2018). Cognitive Training for Agility: The Integration Between Perception and Action. Strength & Conditioning Journal, 40(1), 39-46.

 

• Nimphius, S., Callaghan, S. J., Spiteri, T., & Lockie, R. G. (2016). Change of direction deficit: A more isolated measure of change of direction performance than total 505 time.Journal of strength and conditioning research, 30(11), 3024-3032.

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• Hart, N. H., Spiteri, T., Lockie, R. G., Nimphius, S., & Newton, R. U. (2014). Detecting deficits in change of direction performance using the preplanned multidirectional Australian Football League agility test. The Journal of Strength & Conditioning Research, 28(12), 3552-3556.

 

• Jeffreys, I. (2011). A task-based approach to developing context-specific agility. Strength & Conditioning Journal, 33(4), 52-59.

 

• Jeffreys, I., Huggins, S., & Davies, N. (2018). Delivering a gamespeed-focused speed and agility development program in an English premier league soccer academy. Strength & Conditioning Journal, 40(3), 23-32.

Books:
 

• Nonlinear Pedagogy in Skill Acquisition – Chow, Davids, Renshaw, Button
• Dynamics of Skill Acquisition – Davids, Button, Bennett
• Dexterity and It’s Development - Bernstein
• Routledge Handbook of Sport Expertise – Baker & Farrow
• Motor Learning in Practice – A Constraints Led Approach – Renshaw, Davids, Savelsbergh
• Skill Acquisition in Sport: Research, Theory & Practice – Hodges & Williams
• Developing Sport Expertise: Researchers and Coaches Put Theory into Practice – Farrow, Baker & MacMahon
• Gamespeed – Ian Jeffreys
• The Ecological Approach to Visual Perception – JJ Gibson
• Visual Perception and Action in Sport – Davids, Williams & Williams
• Performance Psychology: Perception, Action, Cognition, and Emotion – Raab, Lobinger, Hoffmann, Pizzera, Laborde
• Thinking In Systems: A Primer – Meadows & Wright
• Complex Systems in Sport – Davids
• Simplexity: Simplifying Principles for a Complex World - Berthoz
• Visual Perception: Physiology, Psychology, and Ecology – Bruce, Green, Georgeson

Podcasts:

• Perception-Action Podcast: Rob Gray
• Player Development Project
• The Talent Equation
• Elite Performance Podcast

Websites:

• Skill Acquisition Science
• Football Beyond The Stats
• ​Train Ugly: Motor Learning Hub
• ​Rebel Movement

INTRODUCTION:

The 1x20 program/philosophy was popularized by Dr. Michael Yessis.  The premise: 15-25 exercises, using one set of 20 repetitions for each exercise.  The goal is to try and hit just about every joint action - so the program involves both multi-joint and single-joint movements in every program.  The philosophy is also to progress from more general exercise selection to more specific exercise selection as the athlete demonstrate amplitude and competency.  

The rationale is each day the athlete gets exposed to a variety of movement patterns, build movement competency under managable loads, allow better ligamentous/tendon adaptations, develops both opportunities for GPP and SPP, and it allows for the minimal effective dose. 

The program consists of certain weeks of 1x20, the progressing to 1x14, and finally 1x8 as the athletes need further, more specific adaptations towards specific physical capabilities 

It has gained popularity with many coaches as a quality model for GPP and for times when coaches are short on time.  A typical session may last only 25-45min, depending on how many movements you have included.  Another proposed benefit of the 1x20, is because the sessions are short and sweet, and don't elicit substantional tissue damage or DOMS, you can train more frequently. These benefits allow for more efficient and effective adaptations for athletes.  

These benefits have been shared anecodotely by coaches, but no research has been done to verify these results in a controlled trial. 

SUBJECTS:

Seventeen male, collegiate baseball pithcers (Age=19.5 years) parook in this study. Subjects were split into 2-groups; 1x20 Program (n=8) and Traditional Program (n=9).  Participants all had at least 1-year of resistance training experience in a S&C program (n=2.7 years)

PROCEDURES:

Particpants were split into 2-groups; 1x20 Training Program (n=8) and Traditional Program (n=9).  All participants underwent pre-testing in the following tests, in the specific order, with the number of trials included in parenthesis 

• Vertical Jump (3)
• Broad Jump (3)
• Single Leg Lateral Jump (2 each)
• 20-Yard Dash (3)
• Throwing Velocity - Crow Hop (5)

Athletes partook in three training sessions per week for 9-weeks (27 total training sessions).  The 1x20 Training Program progressed from 4-weeks of 1x20, 3-weeks of 1x14, and 2-weeks of 1x8. 
The "Traditional" Training (What I would traditinally plan for my pitchers, hence the traditional tag) progressed from a 3-week block of hypertrophy, 3-week block of eccentric and isometric, and 3-week block of power and specificity of transfer.  A similar series that has been used with this pitching staff for the previous 3-years. 

Examples of the training programs are included below for reference. 

RESULTS:

Athletes were omitted from having their results included in the study if they missed 3 or more sessions.  Two athletes were omitted from the results, thus only the results from 17 athletes were used. 
​
The use of paired T-Tests were used to test within and between each experimental groups to determine significance (p=0.05).  

Within Groups

• Traditional Group - Vertical Jump = (p=.058)
• Traditional Group - Broad Jump = (p=.042)

• Traditional Group - Lateral Jump - L = (p=.014)

• Traditional Group - Lateral Jump - R = (p=.001)

• Traditional Group - 20y Dash = (p=.004)
• Traditional Group - Velo = (p=.00)
• 1x20 Group - Vertical Jump = (p=.00)
• 1x20 Group - Broad Jump = (p=.001)
• 1x20 - Lateral Jump - L = (p=.185)
• 1x20 - Lateral Jump - R = (p=.598)

• 1x20 Group - 20y Dash = (p=.00)
• 1x20 Group - Velo = (p=.001)

​​Between Groups

• Vertical = (p=.11)
• Broad Jump = (p=.03) (*1x20)
• Lateral Jump - R = (p=.02) (*Traditional)
• Lateral Jump - L = (p=.14)
• 20y Dash = (p=.82)
• Velo = (p=.00) (*Traditional)

(BOLDED equals statistical significance)​

Comparing the 1x20 Program vs the Traditional Program we see no significant difference in results with the vertical jump, lateral jump (left), or 20y dash.  There was significant difference between the broad jump (1x20 superior), lateral jump (right)(traditional superior), and velo (traditional superior). 
​(All results are shown below in table)

The squat, a movement that most believe is a fundamental pattern to humans; a movement that we should strive to train and maintain for performance and just general wellness. 

It is also a topic of much debate when it comes to HOW to perform a squat...

• What stance?
• What width?
• What toe angle?
• What bar position?
• What variation?
• How deep?

I've worked with close to a thousand athletes and guess what… they all squat differently.  Different stance widths,  different foot positions, different depths, different variation preferences, different bar positions, etc.  

I'm tired of hearing athletes being told they MUST squat a certain way or there is only ONE way to squat… that is rubbish and certainly isn't rooted in science. 

Let's think about this - do you really think someone 6'6 should squat the same as someone 5'2?  Should someone with long femurs and a short torso squat the same as someone with short femurs and a long torso?  Should someone with retroverted hips squat the same as someone with anteverted hips?

If I have a group of 20 athletes and had them all squat with a stance of their preference, to a depth they felt comfortable, with a toe angle that allows the most freedom - you know what I'd find?  20 different squats with different widths, foot angles, depths, trunk angles, etc.  

So why do coaches & PT's still try to jam a square peg into a round hole by thinking there is only one way for people to squat?  You NEED to squat with toes forward, in a shoulder-width stance, to a parallel depth!

Now I'm a man of science, not just anecdotal evidence, so let's see what some of the literature on anatomy and skeletal structure of the hips says and how this may effect the squat

• The femoral neck/head isn't the same in every person.  Zalawadia et al (2010) demonstrated that as much as 24-degrees difference in anteversion and retroversion is common.  Zalawadia also noted that these differences of anteversion and retroversion can differ from side to side - not all hips are symmetrical!  

With sooo much potential variation is peoples hips, not to mention potential side to side difference in the same person - you still think everybody's squat should look EXACTLY the same?  Femoral and acetabulum structure will play the main role in ones ability to squat in certain positions to certain depths - NOT a universal preference made up by some person. 

• Laborie et al (2012) noted that anteversion and retroversion isn't strictly contained to the femoral head, it can also be present in the acetabulum.  They looked at  over 2000 samples of centre-edge angles of the acetabulum  and found angles differed from 20.8-45 degrees

Again, how can we expect someone with a 20.8-degree anteversion to squat the same as someone with a 45-degree retroversion?

• Knutson (2005) looked at leg length, and found that about 90% people have a discrepancy with the average difference of about half a centimeter.
• Flanagan  & Salem (2007) examined different kinetic variables in the squat of 18 experienced lifters. They looked at many things including average joint moments at the hip/knee/ankle, ground reaction forces in each foot, center of pressure for each foot, and maximum flexion angle at the knee/hip/ankle. They found many things (some statistically significant, others not) including side to side differences in center of pressure, ground reaction forces, and joint moments at the ankle, knee, and hip (especially the hip). The researchers concluded that NOBODY was balanced and every subject demonstrated differences in at least on of the joints (ankle, knee, hip)

It is COMMON that people squat with asymmetries and differences from side to side.  It's normal to have someone feel and perform better with one toe angled out/in, staggered forward/backward,   externally/internally rotated compared to the other.  

If pain isn't present - THERE IS NOTHING WRONG WITH THIS - and it's likely aiding in performance, comfort, and health.  We aren't symmetrical beings and sometimes forcing symmetry may actually be taking someone out of their "neutral".  

Want to see what these differences actually look like?  Check out the below photos and see how these skeletal structures can differ and visualize how they'll dictate an athletes optimal squat.

If we tried to take these people and squat them in a toes forward, shoulder width stance, to parallel, what do you think would happen?

Some would ace the test, while others would fail miserably… why?

Much of it would have to do with this structure - NOT some mobility, stability, strength, motor control dysfunction, but rather something they CANNOT change - their bone structure. 

We seem to be in a stage where we see someone who can't squat deep, or prefers a wide stance, or turns their feet turn out, or has butt wink and we jump all over them with how their "insert joint/muscle" is tight/weak and needs soft-tissue, mobility, or activation work, BUT in many situations, no matter what correctives, or soft-tissue, or crazy mobility you throw at the athlete - they just won't be able to squat in certain positions. 

Let's wet our whistle with a little more literature

• Elson and Aspinal (2008) showed what is tremendously obvious for coaches that actually work with people - there are vast differences in range of motion in hip flexion and extension - meaning some people are just better suited for deep hip flexion (deep squat), while this position would cause massive problems for others. 
• D'Lima et al (200) demonstrated that differences in femoral neck/head thickness (as little as 2mm) could impact hip flexor ROM by 1.5-8.5 degrees.  
• Lamontagne et al (2009) looked at people with femoroacetabular impingement syndrome (FAI) and squat ability and concluded due to anatomical variations at the hip such as cam or pincer, there are plenty of lifters who will never be able to deep squat with proper form.

So should everybody squat to parallel or ass to grass?  Should everybody have the same stance width and toe angle?

NO!!!

Some have a tendency for hip flexion (squat deep), while others have tendency for hip extension.  If we force them to parallel or ass to grass we may be forcing bone on bone or a hip impingement - not good things.   The only people that NEED to squat to parallel are powerlfiters, it's a requirement of their sport.  As for athletes, there is no rule book that says you have to squat to parallel or beyond - it's not a requirement nor is it going to make or break performance. 

Again, ones ability to squat to different depths in different stances can be explained by their skeletal structure - NOT necessarily mobility or soft tissue or strength issues.  It also means trying to say everybody should squat the SAME WAY is a terrible thought process and could actually be causing more harm than good. 

Here's a quote from the great Stu McGill, considered the World's foremost expert on spinal health - "The most important matter on all of this is the depth of the hip socket. If people are looking up on the internet, depth of the hip socket and squat ability, they won’t find it. They have to go to the hip dysplasia literature. What they’ll find is that there are groups in the world with very shallow hip sockets (allow greater hip flexion) and some with deep hip sockets (make it difficult for deep hip flexion)."

Even the World's expert says it's structure that dictates deep squat ability, it's NOT some universal standard. 

​Insert pictures of strong peeps, lifting heavy things and what do you see?

No identical stance, depth, toe angle, etc. 

​Why again do we try to force people to squat a certain way, to a certain depth?  Coach athletes as individuals. 

Let's look at some more myths that pertain to squatting

Knee's Can't Go Beyond The Toes

Here is another myth is purported in all areas and there’s little evidence to support this claim. The knees passing beyond the toes is not some universal point where all of a sudden the stresses on the knee become dangerous and every point before that is safe. 

You know what's even more?  Artificially restricting or trying to prevent forward movement of the knees may be detrimental to the hips and back. Fry et al (2003) looked at the effect of restricted squats where a wooden board was placed in front of the lifter that didn't allow the knees to track past the toes.  

​What did they find?  

As expected, the board restricted setting reduced torque on the knees, but increased torque at the hip and low back.  So you take stress on one joint, only to increase it at another - so pick your poison.  
The researchers concluded, "Exercise technique guidelines should not be based primarily on force characteristics for only one involved joint (e.g., knees) while ignoring other anatomical areas (e.g., hips and low back).”   

While shear forces have been shown to increase in the deep squat position with forward knees, the body can handle them appropriately without risk for injury (Schoenfeld (2010)).   The most thorough review of squat depth on knee pain showed the demands on these tissues in a deep squat are well below the maximum that those tissues can withstand (Hartmann et al (2013)).  What's important is not whether the knees go beyond the toes, but when they track beyond toes.
​
Plus, every Olympic lifter of all-time, theoretically should have messed up knees and some PT would tell them they're lifting wrong...

Squat Stance and Squat Variation

Guess what - the type of squat you use isn't vastly different from each other.  EMG between a front squat and back squat aren't that different, with some studies even showing NO STATISTICAL DIFFERENCE in muscle activities between front and back squats.  (Contreras et al (2016); Gullet et al (2009)).  In general, the front squat will lead to slightly more quad activation and thoracic extension strength; while back squat slightly more glute/hamstring activation, but again, the EMG difference between the two isn't as big as people think.   

How about wide stance vs narrow stance?

Wide stance squats tends to activate greater adductor and glute compared to narrow squat, with no difference between quad activation (Escamilla et al. (2001); Paoli et al (2009); Steven & Donald (1999)).  Swinton et al (2012) recently demonstrated exactly this as the researchers showed EMG results for glute activation were significantly higher in a wide stance compared to a narrow stance.  These EMG results also showed that quadricep activation between the stances were identical - concluding, muscle activation wise, a narrow stance isn't superior to a wide stance.  

How about toe angle or hip angle?

Ninos et al. (1997) found no difference in vastus medialis activation between barbell back squats with two different hip rotation angles (feet pointing outwards vs. feet pointing forwards).  While, Pereira et al (2010) found externally rotating the hip to 30 and 50-degrees resulted in greater hip adductor activation with no change in rectus femoris activation, leading the researchers to conclude that squatting to 60-90 degrees of knee flexion with 30 degrees of external rotation maximized muscle activation. 

Again, there is NO LITERATURE supporting the NEED to squat with toes forward! Rather than squatting with your toes forward or pointed out to a predetermined degree and forcing your knees and hips to follow along, you’re better off seeing what hip and knee position feels the strongest and most comfortable, and letting that determine how far out you point your feet (Nuckols (2016))

In a great review of all the variables that effect muscle activation of a loaded back squat, Clark et al (2012) concluded, research of common variations such as stance width, hip rotation, and squat variation (front vs back) do not significantly affect muscle activation.  Turning the toes out, however, only changes the activation of the adductor muscle group. The glutes and quads (the main movers in the squat) are not significantly activated to a greater extent by any of the variables (Clark at el (2012)).  

So we've seen, specific squat variations - wide, narrow, toes forward, toes out, depth - aren't make or break factors when it comes to muscle activation, joint stress, or performance.  

So again, why would be ever think there is only one way to squat and what would make this way superior?  The fact is, there isn't a single strategy to squat and instead should be dictated upon by the individuals unique skeletal structure, limb lengths, past injury history, mobility/stability factors, and biomechanics. 

Here's just a small list of things that influence squat mechanics 

• Foot Wear (elevated heel vs flat heel)
• Long Tibia vs Short Femur
• Short Tibia vs Long Femur
• Short Femur vs Long Torso
• Long Femur vs Short Torso
• Body Mass
• Stance Width
• Toe Angle
• Foot Size (Length)
• Cueing
• Anterior vs Posterior Chain Strength
• Specific Joint Mobility and Stability Strengths and Weaknesses
• Bar Position

Linked below is a really cool website that demonstrates how different body part lengths, stance width, bar positioning, etc effect the outcome of what a squat will look like - again it's basic biomechanics - http://mysquatmechanics.com

Here are some pictures of how simply changing levers, stance width, ankle mobility, and bar position effect the end look of a squat

All-In-All

The goal of this article is to demonstrate there is no universal way to squat and we need to work to allow and find our athletes optimal way to squat based on their individual anatomy, levers, mobility/stability needs, past injury history, etc - and NOT try to pigeon-hole everybody into a certain way of squatting.  

Please share this with anybody you think would benefit and let's stop the squat stupidity from spreading. 

 PS - Below are some squat assessment videos on what we might use to assess our athletes to find their best squatting stance. 

References:

 Clark, D. R., Lambert, M. I., & Hunter, A. M. (2012). Muscle activation in the loaded free barbell squat: a brief review. The Journal of Strength & Conditioning Research, 26(4), 1169-1178.

Contreras, B., Vigotsky, A. D., Schoenfeld, B. J., Beardsley, C., & Cronin, J. (2016). A comparison of gluteus maximus, biceps femoris, and vastus lateralis electromyography amplitude in the parallel, full, and front squat variations in resistance-trained females. Journal of applied biomechanics, 32(1), 16-22.

Escamilla, R. F., Fleisig, G. S., Lowry, T. M., Barrentine, S. W., & Andrews, J. R. (2001). A three-dimensional biomechanical analysis of the squat during varying stance widths. Medicine and science in sports and exercise, 33(6), 984-998.

Flanagan, S. P., & Salem, G. J. (2007). BILATERAL DIFFERENCES IN THE NET JOINT TORQUES DURING THE SQUAT EXERCIS. The Journal of Strength & Conditioning Research, 21(4), 1220-1226.

Gullett, J. C., Tillman, M. D., Gutierrez, G. M., & Chow, J. W. (2009). A biomechanical comparison of back and front squats in healthy trained individuals. The Journal of Strength & Conditioning Research, 23(1), 284-292.

Hartmann, H., Wirth, K., & Klusemann, M. (2013). Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load. Sports medicine, 43(10), 993-1008.

Knutson, G. A. (2005). Anatomic and functional leg-length inequality: a review and recommendation for clinical decision-making. Part I, anatomic leg-length inequality: prevalence, magnitude, effects and clinical significance. Chiropractic & osteopathy, 13(1), 1.

Lamontagne, M., Kennedy, M. J., & Beaulé, P. E. (2009). The effect of cam FAI on hip and pelvic motion during maximum squat. Clinical orthopaedics and related research, 467(3), 645-650.

Ninos, J. C., Irrgang, J. J., Burdett, R., & Weiss, J. R. (1997). Electromyographic analysis of the squat performed in self-selected lower extremity neutral rotation and 30 of lower extremity turn-out from the self-selected neutral position. Journal of Orthopaedic & Sports Physical Therapy, 25(5), 307-315.

Nuckols, Greg.  http://strengtheory.com/how-to-squat/. 2016

Paoli, A., Marcolin, G., & Petrone, N. (2009). The effect of stance width on the electromyographical activity of eight superficial thigh muscles during back squat with different bar loads. The Journal of Strength & Conditioning Research, 23(1), 246-250.

Pereira, G. R., Leporace, G., das Virgens Chagas, D., Furtado, L. F., Praxedes, J., & Batista, L. A. (2010). Influence of hip external rotation on hip adductor and rectus femoris myoelectric activity during a dynamic parallel squat. The Journal of Strength & Conditioning Research, 24(10), 2749-2754.

Schoenfeld, B. J. (2010). Squatting kinematics and kinetics and their application to exercise performance. The Journal of Strength & Conditioning Research, 24(12), 3497-3506.

Steven, T. M., & Donald, R. M. (1999). Stance width and bar load effects on leg muscle activity during the parallel squat. Med Sci Sports Exerc, 31, 428-436.

Swinton PA, et al (2012) A Biomechanical Comparison of the Traditional Squat, Powerlifting Squat, and Box Squat. The Journal of Strength & Conditioning Research 26(7):1805–16​​

The Functional Movement Screen (FMS) is a popular screen used by coaches and sports medicine professionals as a screen for movement competency.  It is composed of 7 movements and scored on a 0-3 scale, where 0 = pain, 1 = couldn't perform the task, 2 = performed task with compensation, 3 = performed task correctly.

The scores from the 7 movements are combined into a final score out of 21.  The score is supposed to predict injury and performance and it is even suggested that scores under 14 predict a greater risk of injury.

The FMS claims to identify compensatory movement patterns that are indicative of increased injury risk and inefficient movement that causes reduced performance. 

                                                That's a pretty big claim and one the FMS has NOT lived up to.  

First and foremost, the FMS is supposed to be a SCREEN and unfortunately practitioners far out-reach the boundaries of a screen when applying the FMS.  The FMS places labels on people and their movement and with anything that places labels, we certainly hope there is some strong evidence that supports these labels. 

This is tremendously important because when someone scores poorly on a test, they get told their chance of getting injured is high and their performance is decreased. This only implants fear and guarding in the client, rather than confidence and overall is a great way to build fear of movement and sport.  Coaches and those in sports medicine NEED to get beyond telling clients that because they score poorly on a test, they'll get injured - this isn't beneficial to anyone.

Again, the FMS is supposed to be used as a screen, NOT a diagnostic tool… it doesn't and should NOT be used to diagnose things.  Yet, I hear people all over, use the FMS to diagnose supposed dysfunction.

It is a baseline screen, and honestly only scratches the surface of what else needs to be assessed. I have heard of athletes who performed the FMS, and then get told rash diagnoses and the things they get told put fear in the athlete basically saying that it's a miracle they can even make it through a day of school with all the dysfunction's they have. 

                                              "You shouldn't squat based on your OH Squat assessment; 
                                  your core is sooo weak; you have tight hamstrings - you shouldn't sprint; 
            you have an asymmetrical rotary stability score - you will get injured if you don't improve it"

Given all radical leaps in faith the FMS asserts, let's take a closer look at various aspects of the FMS and their claims


The FMS claims to identify compensatory movement patterns that are indicative of increased injury risk and inefficient movement that causes reduced performance.


This is the big one I'll address because it claims an awful lot, and as you'll see, without much scientific support.

In order for the FMS, or any screen for that matter, to be a valid indicator of injury or inefficient movement in sport, it is logical that the compensatory movement patterns that are tested during the screen must be the same or similar to those that are performed in sport - which the FMS does not (Beardsley)

• Dossa et al. (2014) studied junior level hockey players to see if the FMS could predict injuries throughout a season.  The researchers concluded the FMS could NOT be recommended as a screening tool for injury prevention.

• McCall et al. (2015) reviewed the scientific level of evidence of three of the most commonly-reported risk factors, screens, and injury prevention exercises in a previously published survey of 44 premier league soccer teams. The FMS was one of the identified screens. They assigned the FMS a grade D, where D = insufficient evidence to assign a specific recommendation.  

• Parchmann et al. (2011) studied the FMS to evaluate whether it was related to sport performance and found there were NO significant correlations between the higher FMS scores and on-field sports performance.

​

• Even the founders of the FMS did a literature review on the FMS and stated “the use of a total FMS score for predicting injury risk should be avoided, as the individual components of the test are not correlated with one another and are therefore not measuring the same underlying variable" (Cook et al. (2014)).

• Several researchers have assessed FMS scores on athletes of different ability levels to see if higher performing athletes scored higher on the FMS compared to lower level athletes.  They found there to be no difference between FMS scores and the level of the athlete.  This shows that the FMS does not and cannot predict performance. (Fox et al. 2013; Grygorowicz et al. 2013; & Loudon et al. 2014). 

• Lockie et al. (2015) found very little correlation between FMS scores and multidirectional speed and jumping tests in healthy male subjects. 

• In addition, many investigations have been performed to assess the correlations between sprinting, jumping, throwing and agility performances and FMS scores and most have found no relationship between any measure of athletic performance and FMS score (Okada et al. 2011; Parchman et al. 2011; Lockie et al. 2015).

• When it comes to predicting injury, Dallinga et al. (2012) reviewed the literature in respect of the tests that could predict a greater risk of injury.  They reported that general joint laxity, the Star Excursion Balance test, age, a lower hamstring-to-quadriceps strength ratio, and a reduced hip abduction range of motion could all predict a higher risk of lower body injuries.  To test an aspect of this injury prediction model, Paszkewicz et al. (2013) investigated the association between total FMS score and Beighton and Horan joint mobility index (BHJMI) in adolescent athletes. They found no correlation between total FMS score and BHJMI index.  We also know the FMS can't target any of the other aspects shown by Dallinga et al. (2012) as being predictive of injury. 

• A major flaw with the FMS is it's ability or lack of ability to distinguish between athletes. Shouldn't we assess individual variances between athletes in different sports?  A baseball player should definitely be assessed differently than a cross country runner or an offensive lineman in football.  Each one of these athletes will exhibit markedly different mechanical adaptations based on the demands of their sport and position.  Whose to say these adaptations are wrong or bad?  "Faulty" movement patterns do not always lead to pain or injury and in many cases these adaptations are what make athletes better performers in their sport.  Guess what, tissues positively adapt and get stronger based on the stresses placed on them… this is why a pitcher's arm will be very different from others - and this IS NOT a bad thing.  Poor posture does not mean its pathological nor does it mean that person will suffer from more musculoskeletal problems.  So can we please STOP TELLING ATHLETES THIS

The FMS Can Predict Injury


Short answer - NO IT DOESN'T

• Schneiders et al. (2011) looked to find normative values in the FMS with young athletes.  They evaluated the FMS based on the assumption that identifiable biomechanical deficits in fundamental movement patterns have the potential to limit performance and render the athlete susceptible to injury.  In this study, the researchers found that healthy individuals and previously injured individuals had the same scores.  So the FMS could not even detect differences in injured individuals compared to healthy ones.  This is of concern as past injury is a main risk factor of future injury. If FMS cannot detect any sign of recent injuries, it seems unlikely that it can detect future risk, let alone be used as a basis for a specific therapy.

• Frost et al. (2013) questioned the ability of the FMS to assess dysfunction. They looked at 21 firefighters who initially performed a standard screen followed by a repeat screen 5 minutes later, but on the 2nd trial participants were given a verbal description of the grading criteria before performing each test. All firefighters improved their scores within minutes of being told what movement patterns were required - The average score improved from 14.1 ± 1.8 to 16.7 ± 1.9 points; remember in just 5-MINUTES.  Therefore, changes in FMS score may not be due to actual improvements in mechanical efficiency such as mobility, stability or coordination of an athlete but rather simply a knowledge of what the task requires.   This isn't the first time this outcome has been shown, as there are indications that subjects may deliberately alter their movement patterns during the FMS test in order to score higher (Teyhen (2012); Schultz (2013)).  This is supposed to be a reliable screen?

​

• To piggyback the last bullet point - The FMS sum score appears to be very reliable between raters (inter-rater) and within raters for a video of the same test (intra-rater). However as we just discussed, test-retest is less reliable, indicating that the same subjects may score differently on different occasions, despite there being no biomechanical changes made (Beardsley).

• Okada et al. (2011) studied the relationship between FMS scores and "core" strength on actual sport performance.  To keep beating a dead horse, it was found "core" strength and FMS scores are NOT strong predictors of sports performance… yet PT's continues to tell clients/athletes core strength and quality FMS scores are important for performance and pain.

• As I said earlier, it has been suggested that scores under 14 predict a greater risk of injury.  BUT, O'Connor et al. (2011) demonstrated that scores of 18 or more were more at risk for injury than those who scored less than 18 in 874 marine officers.  Scores above 14 are supposed to have decreased risk of injury, not the opposite, especially with a score so close to being perfect. 

These 7 Tests Predict Global Movement?

At the end of the day, it is a far stretch to think these 7 tests somehow can predict an athletes global movement, especially when the athlete is under load, speed, chaos, and fatigue. 

Yet, some believe that these slow, safe, pre-planned, mostly static tests will predict dynamic movement.   It's one thing to do tests in a very controlled, passive type of environment compared to dynamic. I've seen a lot of good things in table assessments or FMS type screens, only to go to HELL under speed or load… Let this be clear, while these screens can have some benefit, they tend to have absolutely NO transfer to dynamic, reactive, and chaotic environments such as sport.

For example, what do we gain from the Overhead Squat (OHS)?

Let's be real here, using the OHS as an assessment of general movement ability, is like using a tennis serve to test coordination (Quote from Dr. Cobb of Z-Health).  The OHS is arguably the most complex version of a squat.  So instead of starting with a baseline test and a more basic squat version, we skip A-Y and go straight to Z. In addition, squatting while reaching overhead is not something that humans are designed to do. It is a skill, and anybody, the first time you ask them to perform something that is completely new to them will struggle.  Chances are, the faults you find in the OHS are due to a lack of performing this specific task as opposed to a lack of good general movement patterns.

Also, why are no other squat assessments used, such as adding a counter-weight (clarify mobility vs stability needs), taking a wide stance, letting toes track outward, using an asymmetrical stance, etc.

Nope, instead the FMS forces everybody to take a shoulder width stance with toes forward and discounts the fact that everybody's hip anatomy is different and to say that you need to be able to OHS with a shoulder-width stance, with toes forward is absurd… how are we still on this? Take a look at the pictures below and tell me if these people should be judged on the same squatting scale given their vastly different anatomical structures. 

It's like trying to fit a square peg into a round whole when we say you should be able to squat in this stance at this depth and apply it to the whole population.

References:

       Beardsley - https://www.strengthandconditioningresearch.com/functional-movement-screen-fms/#CONT

       Cook, G., Burton, L., Hoogenboom, B. J., & Voight, M. (2014). Functional movement screening: the use of fundamental movements as an assessment of function-part 2. International journal of sports physical therapy, 9(4), 549-563

       Dallinga, J. M., Benjaminse, A., & Lemmink, K. A. (2012). Which Screening Tools Can Predict Injury to the Lower Extremities in Team Sports?. Sports medicine, 42(9), 791-815

       Dossa, K., Cashman, G., Howitt, S., West, B., & Murray, N. (2014). Can injury in major junior hockey players be predicted by a pre-season functional movement screen–a prospective cohort study. The Journal of the Canadian Chiropractic Association, 58(4), 421.

        Fox, D., O’Malley, E., & Blake, C. (2014). Normative Data for the Functional Movement Screen™ in Male Gaelic Field Sports. Physical Therapy in Sport.

       Frost, D. M., Beach, T. A., Callaghan, J. P., & McGill, S. M. (2013b). FMS™ scores change with performers’ knowledge of the grading criteria-Are general whole-body movement screens capturing” dysfunction”? The Journal of Strength & Conditioning Research.

       Grygorowicz, M., Piontek, T., & Dudzinski, W. (2013). Evaluation of Functional Limitations in Female Soccer Players and Their Relationship with Sports Level–A Cross Sectional Study. PloS one, 8(6), e66871

       Lederman E. The Myth of Core Stability. Journal of Bodyworks Movement Therapy. 2010 Jan;14(1):84–98.       

          Lockie, R. G., Schultz, A. B., Jordan, C. A., Callaghan, S. J., Jeffriess, M. D., & Luczo, T. M. (2015). Can selected functional movement screen assessments be used to identify movement deficiencies that could affect multidirectional speed and jump performance?. The Journal of Strength & Conditioning Research, 29(1), 195-205

         Loudon, J. K., Parkerson-Mitchell, A. J., Hildebrand, L. D., & Teague, C. (2014). Functional movement screen scores in a group of running athletes. The Journal of Strength & Conditioning Research, 28(4), 909-913

          McCall, A., Carling, C., Davison, M., Nedelec, M., Le Gall, F., Berthoin, S., & Dupont, G. (2015). Injury risk factors, screening tests and preventative strategies: a systematic review of the evidence that underpins the perceptions and practices of 44 football (soccer) teams from various premier leagues. British journal of sports medicine.

       Okada, T., Huxel, K. C., & Nesser, T. W. (2011). Relationship between core stability, functional movement, and performance. The Journal of Strength & Conditioning Research, 25(1), 252-261

       O’Connor, F. G., Deuster, P. A., Davis, J., Pappas, C. G., & Knapik, J. J. (2011). Functional movement screening: predicting injuries in officer candidates. Med Sci Sports Exerc, 43(12), 2224-30.

       Parchmann, C. J., & McBride, J. M. (2011). Relationship between functional movement screen and athletic performance. The Journal of Strength & Conditioning Research, 25(12), 3378-3384.

       Paszkewicz, J. R., & Cailee Welch McCarty, D. (2013). Comparison of Functional and Static Evaluation Tools Among Adolescent Athletes. The Journal of Strength & Conditioning Research.

       Schneiders, A. G., Davidsson, Å., Hörman, E. & Sullivan, S. J. (2011). Functional movement screenTM normative values in a young, active population. International Journal of Sports Physical Therapy, 6(2),75.​
        Shultz, R., Anderson, S. C., Matheson, G. O., Marcello, B., & Besier, T. (2013). Test-Retest and Interrater Reliability of the Functional Movement Screen. Journal of athletic training, 48(3), 331-336

       Teyhen, D. S., Shaffer, S. W., Lorenson, C. L., Halfpap, J. P., Donofry, D. F., Walker, M. J., & Childs, J. D. (2012). The Functional Movement Screen: a reliability study. The Journal of Orthopaedic and Sports Physical Therapy, 42(6), 530-40   

       Unsgaard-Tøndel M, Fladmark AM, Salvesen O, Vasseljen O. Motor Control Exercises, Sling Exercises, and General Exercises for Patients With Chronic Low Back Pain: A Randomized Controlled Trial With 1-Year Follow-up. Phys Ther. 2010 Jul.

There is a fascination in the Strength and Conditioning world with triple extension.  For those not familiar - triple extension is extension of 3 joints - ankle, knee, and hip.

In fact, achieving triple extension has become, in many cases, the main priority in exercise selection.

Why has triple extension become a prized possession when training athletes?

Well it has been proposed as a key in athlete performance, mainly imho, because when you look at still pictures of jumping or accelerating or sprinting coaches perceive the key performance indicator behind these movements is triple extension.

Go into Google and type in Triple Extension and here are some of the top images...

As you can see, Olympic lifting is very closely associated with triple extension and hence why it is thought to be a valuable training tool. 

BUT, BUT what if I told you triple extension is far overrated?  What if triple extension occurs FAR FAR LESS than what you've been told?  What if I told you triple extension has only a small amount to do with athletic success?

For many it would be blasphmaomy, but let's take a deeper look at triple extension.

First, let's take a look at these picture and tell me if triple extension is occurring…

When it comes to sprinting, triple extension does NOT occur.  During top-end sprinting neither full hip, knee, or ankle extension occurs. 

In fact, the more extension one gets, the slower they will run.  In order to maximize speed, less active ankle, knee, and hip extension occurs, and the sooner flexion in these joints occur during and immediately after Ground Contact, the better.

Understand this, during top-end speed, the athlete is only on the ground for .07-.13seconds, this is no where near enough time for someone to fully extend each joint, and the more they try to, the slower they would run.  The best sprinters have less hip and knee extension at toe-off

If an athlete tried to triple extend, they would create excessive backside mechanics which leads to long, inefficient GCT, and further lead to poor flight positioning of the swing leg which would finally result of the swing leg contacting the ground out in front of the body, rather than closer to the COM.  

​It's a deadly cycle.

During acceleration, athletes MAY triple extend during their first 1-2 steps, but after that - triple extension DOES NOT occur.  Same as top-end speed, their simply isn't enough time on the ground, and extension power should be put forth during ground preparation and during the 1st half of GCT - the goal during ground contact is to get off the ground as quickly as possible.

Let's take a look at some great charts by James Wild (@wildy_jj)

The below chart shows that full hip extension doesn't occur during the 1st 3-steps, and this is amplified in team sport athletes - who are less technically proficient as sprinters.

This chart shows knee extension during the 1st 3-steps, again full knee extension is no where to be found.

This chart shows ankle extension, again the less ankle extension, the better the performance.  â€‹

When it comes to the vertical jump, Chang et al. (2015) demonstrated that vertical jump performance was not dictated by triple extension.  Instead, successful performance in the vertical jump could be described by knee and ankle extension, not hip extension.

In fact, I think triple flexion is on the same level of triple extension.  Flexion angles of the hip, knee, and ankle are vitally important for sprinting speed.  Ankle dorsiflexion is a must during sprinting, COD, and braking actions.  Hip flexion is a must to allow the body to produce maximal forces during sprinting, acceleration, and jumping.  Triple flexion allows the body to create a ton of stored elastic energy to be reproduced during extension phases.  Triple flexion is the loading, coiling, and absorbing - extension is uncoiling and expression.

This chart shows the LESS ankle dorsiflexion range equals faster speeds… in normal english, this means the less the ankle deforms at GCT the better - so coming into GCT with MORE FLEXION can help allow less deformation, better utilization of stored elastic energy, and shorter GCTs.

At the end of the day, triple extension plays a role in athletic performance, but let's be clear - it's a lot less important than most claim. 

Being able to produce extension forces IS very important, but they are not necessarily end range of motion extension forces. 

So the moral of the story is this - if you're choosing your exercises/programming based on achieving triple extension, take another look because that is a poor reason to include or exclude certain exercises. 


Got Get 'Em!



References

Chang, E., Norcross, M. F., Johnson, S. T., Kitagawa, T., & Hoffman, M. (2015). Relationships between explosive and maximal triple extensor muscle performance and vertical jump height. The Journal of Strength & Conditioning Research, 29(2), 545-551.

Here's a novel idea for S&C coaches, and one that I feel will give us a better evaluation of the impact a S&C has.

Why don't you ask your athletes, or coaches?  

Ask your athletes if they feel they are improving in all areas of athletic performance.  

This means a lot more than just purely strength.  Are they improving movement skills, increasing usable range of motion, getting faster, are they more confident and resilient, do they believe in the program and buy-in to what you are doing, are their specific conditioning and ESD demands improving?

Below is a questionnaire I gave to 153 of my athletes and to 3 sport coaches to fill out and asked them to be brutally honest with their responses.  

This might seem very scary or exposing for a coach, but doesn't it make sense to actually get a sense of what those experiencing your coaching are feeling? 

If you are afraid of what your athletes and coaches will write, then that alone should tell you something.  You should be excited and confident to hear the responses and use the info to make yourself an even better coach.

Here are the simple questions I asked.  The 153 athletes I asked included athletes from 7th grade – seniors in college - to professional athletes.   They didn't put their name on the sheet and again I told them to be brutally honest, my feelings wouldn't be hurt! 
 
1.     Male or Female?

2.     What is your favorite part of this S&C program?

3.     What is your LEAST favorite part of this S&C program?

4.     What is your favorite exercise?

5.     What is your LEAST favorite exercise?

6.     What do you wish we’d do more of?

7.     What do you wish we’d do less of?

8.     Do you feel you have improved since we've started to now?   In what areas do you feel have improved the most? 

9.     In what area do you feel you're stagnating or feel we could a better job addressing? 

10.     If you could change 1 thing or make 1 suggestion to this S&C program or for how I can improve as a coach, what would it be?


It was honestly refreshing to receive this feedback and delving into the information has been very beneficial to me as a coach – I urge you to do the same. 

After going over all the responses 3-4 times, a couple of things really stand out to me as interesting, and I think can really help all coaches out there.   Here they are in no particular order.


Have Fun

One of the common themes in the feedback was that just about every response said their favorite aspect was how I made the program fun and the enjoyed the games/competitive aspects of the program.

Let me repeat that:

All ages, even professional and high level college athletes all stated they enjoye games, competitions, and play

We are a species that enjoys and thrives with play.  

One reason I dislike the idea of working in bigger college or professional settings is they tend to be really serious.  Their athletes can't be having fun or involved in "silly" games, and this is something I whole-heartedly disagree with. 

Not only do games and play-type environments enhance the enjoyment and fun for the athletes, but they also encourage the use of creativity, open-sided and reactive movements, stimulate cognitive function and recognition, encourage competition, and involve strategy and communication with teammates. 

Please tell me how this isn't beneficial for athletes?

Moral of the story, find ways to make your training more game-based, open, and competitive.

Least Favorite Exercise 

Everyone hates Iso BSS lol

Morning Training? 

People do not like early morning lifting, especially if the are doing it 3-4 times a week.  And to be honest, I really don't enjoy as a coach either.  I've been getting up at 4:45am, every weekday, for 4+ years, and I'd be lying if I said I absolutely love it when my alarm goes off. 

What's interesting to me is we know the importance of sleep and how a lack of sleep has numerous negative effects on various areas of an athletes health and performance, but we continue to ask for 5:30 or 6:00am lifting sessions?

Obviously, those of us working in a University setting are restricted by things we simply can’t get around.   The fact is we work with student-athletes and they tend to have classes from 8am-2pm and there aren't a plethora of time options for training times.

But can we shift the believe that these early morning sessions are essential??

I breakdown all of my college athletes sleep and bed times on a DAILY basis, and it’s rare to see these athletes in bed before 11pm despite the urging and preaching about the importance of sleep.  I can get pissed at them and try to educate them until I'm red in the face, but what better am I if I then go and have them train at 6 or 7am, for 3-4 times a week, knowing they are only getting 6-7 hours of sleep each night.  

Obviously education is a integral part to helping our athletes and trying to get them to buy-into getting to bed earlier and improving their sleep habits, but I also feel we as coaches are often hypocrites when we continue to make them be up at 5am each morning.  

The feedback I received was very clear, they do not like getting up for 6am workouts.  My thoughts are this - if we can avoid these early morning sessions, then we absolutely should.  Obviously in a college setting, with limitations of resources, class conflicts, etc - then yes we need to use these early morning time-frames, but maybe we need to find ways to rotate teams, so it's not the same teams/athletes doing 6am every single day.

I look at it as, if we can even reduce a specific team needing to train at 6am, just 1-day a week, we are likely adding 3-5 additional hours of sleep a week for these athletes - which could be huge for performance and recovery. 


Buzz Words 

Athletes have a decent understanding of buzz words and they want to perform those buzz words.  

 In the question, what do you wish we did more of – three common responses occurred.  

1. Core
2. Explosive Exercises  
3. Arms

Two of the three responses would be what I would consider buzz terms.  Athletes probably couldn't even tell you what the "core" is or what muscles make up the "core", to them it just means abs.

Maybe throwing in an ab or arm burner at the end of sessions is a good idea from time to time.  Plus these won’t negatively effect or pull away from the CNS stimulus you're trying have the body adapt to.
  
Those questioned also tended to make notes to wanting to do more explosive type exercises.  We know we perform different med ball variations or jumping/bounding movements to train various power production applications, but do they?  

Just adding, hey this is to work on our explosiveness, might be something they really want to hear and enhance the intent of the drill.

Conclusion 

Well I hope this sheds some light as a way to give greater insight into your coaching.  I think ever coach should give this questionnaire at the end of a semester or year and really evaluate what you are doing as a coach.  This will definitely be something I address with my athletes and coaches every year from here on out and I encourage you to do the same or share your results as well!  

For anyone that has done research or submitted to a journal, knows the amount of time, detail, revisions, and head-ache that goes into writing and researching for a paper.

Writing a proposal, getting proposal approval, getting IRB approval, collecting subjects, data collection, data analysis, submission to journals, rejection, another submission, revisions, re-submission, more revisions, re-submission, and finally acceptance.  This process can take anywhere fem 6-18months from start to finish; not to mention the tons of stress and time and loss of confidence that comes from writing, sifting through hundreds of research articles, inevitable rejection, double digit revisions, and wondering if your work will ever be accepted.

For those of us who are full-time coaches, it is difficult to find the time and energy to dedicate to this type of consistent research.

With that being said, I do think every S&C coach should strive to produce a real scientific paper and be published by a journal.

There are a couple of reasons for this.

1. We have access to real athletes -  something a lot of research is missing
2. Give back and further the education of our field
3. Appreciate and understand of how difficult, tedious, and in-depth research can be.  It's a pet peeve of mine when coaches, who have never published research, criticize those that do.  You'll be humbled when you go through this process

While I do enjoy the process and the opportunity to have work published, I also know there is simply not enough hours in the day to get all the data I track published into a journal.

So instead, I will label articles in this section as BBA Journal of Sports Performance.  This will be where I can dump research that we're conducting at BBA, but aren't working to get published into a journal.

With that being said, this work will all be conducted in a scientific manner - clean procedures, proper set-up, detailed data collection, and inferential data analysis.  There will be less detailed introductions and discussions - just want to present the data with a few closing thoughts.

The overall goal is for this data to be more than anecdotal or what another pet peeve of mine is when coaches say, "We've seen great results from INSERT EXERCISE/TOOL/MODALITY".  Yet, they cannot produce results, a control group, or inferential statistics to validate their claims.

So without further ado, let's go into this BBA Journal Study.
​

EFFECT OF VARIOUS POST-ACTIVATION POTENTIATION 
TECHNIQUES ON COUNTERMOVEMENT JUMP
​

INTRODUCTION:

Post-Activation Potentiation (PAP) is the concept of applying a conditional activity (CA) to improve the proceeding activity.  Great sport scientist Yuri Verhoshansky was the first to describe the effects of PAP and investigate them in a chronic training program (7).   Verkhoshansky recommended performing explosive and plyometric movements after resistance movement to take advantage of the possible heightened excitability of the central nervous system.

While Verkhoshansky generally stated "heightened" excitability - the exact mechanisms that effect PAP are not 100% quantified, but it's likely a combination of muscular and neural interplay.  Increased neural activity may occur through recruitment and synchronization of motor units, a decrease in presynaptic inhibition, or import more central nerve impulses (3).  A CA may also lead to the phosphorylation of myosin regulation light chains (4,5).  This mechanism is mainly attributed to actin-myosin interaction via Ca2+ released from the sarcoplasmic reticulum (6).  Myosin light chain kinase, which is responsible for making more ATP available at the actin-myosin complex increases the rate of actin-myosin cross-bridging.   This leads the CA to increase the power output of the cross bridges and this in turn improves the performance of explosive movements (6).

In basic terms, the idea of PAP is to stimulate or excite the nervous and muscular system to improve the RFD, power, and speed of the following activity. The CA can be anything from heavy loaded lifts, power movements, or elastic activities. 

PAP has been heavily studied, and overall PAP has been shown to be effective, but with many caveats.  Seitz et al. (2015) did a meta-analysis on PAP factors on jumping, sprinting, throwing, and upper-body ballistic performance (1). The researchers reviewed all pertaining research and found the following trends to be effective for PAP performance. 

• A larger PAP effect is observed among stronger individuals and those with more experience in resistance training 
• Plyometric (ES = 0.47) CAs induce a slightly larger PAP effect than traditional high-intensity (ES = 0.41), traditional moderate-intensity (ES = 0.19), and maximal isometric (ES = -0.09) CAs 
• Greater effect after shallower (ES = 0.58) versus deeper (ES = 0.25) squat CAs, longer (ES = 0.44 and 0.49) versus shorter (ES = 0.17) recovery intervals, multiple- (ES = 0.69) versus single- (ES = 0.24) set CAs, and repetition maximum (RM) (ES = 0.51) versus sub-maximal (ES = 0.34) loads during the CA.  
• It is noteworthy that a greater PAP effect can be realized earlier after a plyometric CA than with traditional high- and moderate-intensity CAs. Additionally, shorter recovery intervals, single-set CAs, and RM CAs are more effective at inducing PAP in stronger individuals, while weaker individuals respond better to longer recovery intervals, multiple-set CAs, and sub-maximal CAs. 
• Both weaker and stronger individuals express greater PAP after shallower squat CAs. 
• Performing a CA elicits small PAP effects for jump, throw, and upper-body ballistic performance activities, and a moderate effect for sprint performance activity. 
• The level of potentiation is dependent on the individual's level of strength and resistance training experience, the type of CA, the depth of the squat when this exercise is employed to elicit PAP, the rest period between the CA and subsequent performance, the number of set(s) of the CA, and the type of load used during the CA. 
• Finally, some components of the strength-power-potentiation complex modulate the PAP response of weaker and stronger individuals in a different way. 

For these reasons, you'll likely see the implementation of PAP strategies within a sports performance environment. The meta-analysis from Seitz et al. (2015) showed the benefits from a CA of plyometrics on the proceeding activity, but previous literature is heavily favored towards the CA being a resistance training movement such as moderate to heavy back squats. To further investigate this plyometric effect, this study hopes to examine three different variations of plyometric activity - resisted, assisted, and depth jump. 

Band assisted CMJ training was shown to be more effective than traditional BW CMJ training in high level volleyball players (1).  These researchers concluded that assisted jumping may promote the leg extensor musculature to undergo a more rapid rate of shortening, and chronic exposure appears to improve jumping ability (1).

SUBJECTS:

Twenty-one male, collegiate baseball athletes (age=20.33) partook in this study.  There were three groups of five subjects, and one group of six subjects.  All subjects had at least 1-year of resistance training in a S&C program (avg=2.23years)

PROCEDURES:

Participants were randomly split into 4 groups (n=5; n=5; n=5; n=6).  Over the course of 2-weeks (Week 1 = Mon, Fri; Week 2 = Mon, Fri) participants came in and were tested.  Each testing day, each group underwent one of four conditions - Depth Jump (DJ), Band Resisted CMJ (Rest), Band Assisted CMJ (Asst), or Control (Con).  Each group was subjected to each of the four conditions over the four testing days. 

After performing the same dynamic warm-up each day, each group followed the below procedures.  Each group was given the same instructions - "Jump as high as you can and also as fast as you can off the ground".

• DJ Group = 2x5 Depth Jumps off a 20" Box.  Rest periods - 20sec between each rep; 2min between sets.

• Rest Group = 2x5 Band Resisted CMJ.  Rest periods - Reps performed in a continuous action; 2min between sets.

• Asst Group = 2x5 Band Assisted CMJ.  Rest periods - Reps performed in a continuous action; 2min between sets. 

• Control = Went directly to CMJ testing. 

After undergoing the experimental effect, the subjects received a 2-minute rest and then performed 3 CMJ trials with 30sec of rest between trials.  Overall 63 trails were recorded for each experimental group.  


RESULTS:

The use of paired T-Tests were used to test between each experimental groups to determine significance (p=0.05).  The results are below.

• Depth Jump (DJ) was superior to Control (p=0.00) 
• DJ was also superior to Resisted (p=0.00) 
• DJ and Assisted had no statistical difference (p=0.217) 
• Assisted was superior to Control (p=0.00) 
• Assisted was also superior to Resisted (p=0.036) 
• Resisted was superior to Control (p=0.003)

Below are the average CMJ scores (in inches) after each of the experimental applications. 

APPLICATION:

Given these results, a coach, athlete, or sport that requires great performance in the CMJ, may consider adapting a warm-up or conditioning activity that includes depth jumps or band assisted jumps.  Even the use of band resisted jumps elicits superior results than doing nothing at all, but this route is inferior to both depth jumps and band assisted. 

Sports or environments like track and field, volleyball, NFL combine, and NBA combine all may benefit from these results.  It would also be beneficial for future research to evaluate the long-term effects of such training measures. 



References:

1. Seitz, L. B., & Haff, G. G. (2015). Factors Modulating Post-Activation Potentiation of Jump, Sprint, Throw, and Upper-Body Ballistic Performances: A Systematic Review with Meta-Analysis. Sports Medicine, 1-10.

2. Sheppard, J. M., Dingley, A. A., Janssen, I., Spratford, W., Chapman, D. W., & Newton, R. U. (2011). The effect of assisted jumping on vertical jump height in high-performance volleyball players. Journal of science and medicine in sport, 14(1), 85-89.

3. Tillin NA, Bishop D. Factors Modulating Post-Activation Potentiation and its Effect on Performance of Subsequent Explosive Activities. Sports Med. 39 (2): 147-166, 2009.

4. Rassier DE, MacIntosh BR. Coexistence of potentiation and fatigue in skeletal muscle. Braz. J. Med.Biol. Res.  33(5):499–508, 2000.

5. Rassier DE, MacIntosh BR. Coexistence of potentiation and fatigue in skeletal muscle. Braz. J. Med.Biol. Res.  33(5):499–508, 2000.

6. Christos, K. (2010). Post-activation potentiation: Factors affecting it and the effect on performance. Journal of Physical Education and Sport, 28(3).

7. Verkhoshansky Y, Tetyan V. Speed-strength preparation of future champions. Legkaya Atleika. 2:12–13 , 1973.

So What Happens?


As running speeds increase so do the activation of specific muscle groups causing different joint actions.  These increases are necessary for faster running speeds and knowing when and how these groups interact is important to help train speed.  What is especially important in regards to sprinting and acceleration, is the available time to produce force in most cases is less than .20-sec!  This means muscle contraction velocity, not necessarily maximal muscular force is key in faster running speeds. 

This isn't to say muscular force isn't important, but chasing peak muscular force, when an athlete cannot produce maximal muscular contractions in the necessary time frames is a circular endeavor. 

As an athlete increase his or her speed, muscles are shortened at increasingly higher velocities and have less and less time to generate the maximal forces.  What this means is that many factors, such as elastic response, pre-tensing, and joint stiffness are extremely important. 

With all that being said, specific musculature plays important roles during sprinting, whether it be concentrically, isometrically, or eccentrically in nature. 

Let's take a look at these muscle groups and the when, how, and what they do during the sprinting cycle.


Posterior Chain

The first hip extensor we'll look at are the glutes.  The glutes, specifically the glute max and glute medius, are maximized during ground contact to contribute to vertical support and stabilize the pelvis/hip to help prevent swinging, dropping, and over-rotation.

While the glute max does contribute and influence hip extension during ground preparation, it's major role is during ground contact to stabilize, resist deformation, and continue to transmit the energy built during ground prep.  In this position, the glutes are in a shortened position, and act in a very isometric manner.

It is apparent that at the start of the ground contact phase, at the point that the lead foot touches the ground, the hamstrings are functioning at relatively long muscle lengths. In contrast, at the same point in time, the gluteus maximus is functioning at a much shorter muscle length. Resistance training exercises often develop strength at specific joint angle ranges of motion depending upon their point of peak contraction. Therefore, these findings may be relevant for identifying the optimal resistance training exercises for training the hamstrings and gluteus maximus for optimal performance during sprint running. The hamstrings may benefit from being trained with exercises that involve a peak contraction at long muscle lengths, while the gluteus maximus may benefit from being trained with exercises that involve a peak contraction at short muscle lengths.

Ralph Mann, the famous sprint researcher, reported the best sprinters have the greatest hip extensor moments.   Bezodis et al. (2008) and Bezodis et al. (2009) both remarked upon the large hip extension moments that occurred during sprint running, providing strong support for their importance.

As the leg drives down towards the ground (what we call ground preparation), the hip extensors are the driver behind these forces and accelerating the leg, powerfully into the ground.

The next hip extensor we'll look at is the hamstring group.   The hamstrings are made-up of 3 muscles - bicep femoris, semitendinosus, and semimembranosus.  The group as a whole, is very active during the sprinting cycle and put under a ton of stress.

The hamstring group have the longest duration as they start activity at the beginning of ground preparation (at maximal hip flexion), and eccentrically contract - distally; while concentrically contract - locally, as they prepare for ground contact.   A recent review studied the mechanics of the hamstring during sprinting, here's what they found (6).

• The long head of the bicep femoris had the largest peak musculotendon strain (12.0% increase)
• The semitendinosus had the greatest musculotendon lengthening velocity.
• Semimembranosus produced the highest musculo-tendon force, absorbed and generated the most muscul-tendon power, and performed the largest amount of concentric and eccentric work.

As you can see, all the hamstring muscle undergo large changes in muscle length, but especially the bicep femoris with the greatest peak musculotendon strain which corresponds with the bicep femoris being the most injured hamstring muscle.   Overall, all the hamstrings are stretched to great degrees during ground preparation and at ground contact and the eccentric hamstring action during ground preparation is both reason for successful sprinting, but also increased risk of injury.

The hamstrings are the primary propulsive muscles during sprinting and as you can see above, they store elastic energy during the lengthening actions they go through which is then released at ground contact.

Unlike the glutes, hamstring force is lower during ground contact and higher during group prep.  This leads to a statement I use, and it leads to training methods for these muscles.

                                                                         "Glutes on the ground, hamstrings in the air"

The glutes work in a shorted position, isometrically at ground contact.  The hamstrings work eccentrically at the knee and concentrically at the hip, use a lot of stored elastic energy during ground preparation.  Studies have shown that mirroring your training to be specific to these actions of the hip extensors (eccentrically and elastically) to be successful in preventing and rehabbing from injury (9,10). 


Anterior Chain 

The anterior chain doesn't get as much love as the posterior chain, but they do play an important role during the sprinting cycle and are valuable in enhancing sprinting speed.

The first group we'll look at is the hip flexors, mainly the illiopsoas.  Two proposed ways increasing hip flexion strength increases sprinting speed is first it leads to a faster repositioning of the leg to get back to frontside mechanics. Second, the hip flexors are active during take-off and early flight to stop the leg from continuing to travel backwards and start the forward motion of the knee, this occurs in a stretched position and relies a lot on stored elastic energy.

Either way, hip flexion strength and cross sectional area has been positively correlated with faster sprinting speed (1,2,6,12)

Why are the hip flexors important?  Faster sprinters exhibit greater hip flexion and front side mechanics angle compared to slower sprinters (7).  At toe-off, the hip flexors are put under great stretch and the elastic components resist further hip extension and act like a rubber band to "snap" the hip back forward.

This means, the hip flexor complex needs to be trained at length and be able to utilize stored elastic energy to stop hip extension and "snap" the leg back to reach front-side mechanics. 

Another important aspect of the hip flexor group, is flexibility.  Riley et al. (2010) suggested that hip flexor mobility may play a role in the utilization of hip extension range of motion during running.  If contralateral hip flexor is adequate, proper and full hip extension can take place without running into restriction or co-contraction of the hip flexor group. 

The second part of the anterior chain is the quadrupeds group.  During the beginning of ground contact, the quadriceps eccentrically contract to stabilize the knee joint.  The primary role of the quadruped group is to provide high degrees of joint stiffness to support and absorb the vertical fall of the athlete.


Lower Leg

Ankle stiffness is key to transfer force produced up the chain into the ground and for muscles up the chain to work optimally.  For example, having instability in the ankle joint decreased the activity of the glute max by over 25% (3).  Instability goes in both directions - can't transfer force and leads to bigger engines not producing maximal force. 

We tell our athletes this analogy all the time.

                                      Having weak feet/lower leg is like having flat tires.  Even if you are driving a ferrari, 
                                                                             if you have flat tires the car won't go fast. 

It's the same thing with the feet/lower leg.  If they are weak, maximal force won't be transferred into the ground. 

The lower leg needs incredible amounts of isometric strength to resist the 4-6xBW forces being put onto them.  Longer duration, low-magnitude plyometrics are a great way to build lower log/foot strength, and as athletes progress high-magnitude plyometrics are great to simulate the GRF of sprinting.


Arms

Arms are an interesting topic in sprinting and do not play as big as a role as many state.  Let's be clear, the arms are neither the key to sprinting fast nor absolutely unnecessary to sprinting fast. They do play a role and assist in sprinting speed, specifically assist in horizontal propulsion during acceleration and vertical force during top-end sprinting, and they also help to counterbalance the rotary actions of the legs.  If one were not to use their arms, they wouldn't be able to control the rotation the leg put onto the trunk.  So, in a sense the arms help to maintain and streamline the efficiency of the sprinting cycle. 

There are a couple of misconceptions about the arms... THEY DO NOT LEAD THE LEGS and THEY DO NOT STAY LOCKED AT 90-DEGREES. 

We want to see the arms act in opposition of the legs while also matching timing and magnitude of the legs.  Finally, it is fully expected to see extension and flexion at the elbow joint during forward and backward swing, and these should also match each other (elbow flexion on forward swing should be matched by elbow extension on backward swing).


Practical Applications

Knowing what and when things happen during the sprint cycle means a lot in terms of dictating a training plan.  When we think of muscles, we think about strength, and when we think of strength, especially lower body - we think squat, deadlift, and maybe the Olympic lifts. 

While these things do inherently play a role, I highly doubt increasing squat or deadlift or Olympic lift strength will lead to greater horizontal or vertical forces during the sprinting cycle.  I think it would be very interesting to compare GRF during acceleration and top-end speed with strength in your typical lifts - squat, deadlift, Oly's.  I'm really skeptical that strength in these lifts relates to higher GRF's, vertical or horizontal, during acceleration and/or top-end speed. 

For higher level of mastery athletes, using these tools are limited at best and specific tools need to be used to enhance the qualities discussed in this article.  In fact, multiple research reviews have shown that traditional strength training is moderate at best for improving sprinting speed, and this relationship goes down as the level of the athlete increases (13,14).  And for those who think the almighty squat is the key to speed, know that wussy movements like the bulgarian split squat and unilateral jumps appear to more effective at enhancing speed (15,16,17).

Specificity is a must for high transfer to sprinting speed, especially for higher level athletes.  For example, the hamstrings are active during ground preparation, when the hip is flexed and the knee extends eccentrically.  This is in opposition of what many hamstring specific exercises or rehab program utilized.

Understand that strengthening the hamstrings are best trained at long lengths and eccentrically where the hip is kept in flexion.  Also, using SSC concepts on the hamstring prepares the body for specific transfer to performance (10,11).  Lastly, remember,

"Glutes on the ground, Hamstrings in the air"
​
Training the hamstrings in a unilateral, open chain manner is specific to the manner of execution an athlete needs.  Here are some ideas for training the posterior chain for greater transference to sprinting speed.

Here are some for the anterior chain

References:

1.  Deane, R. S., Chow, J. W., Tillman, M. D., & Fournier, K. A. (2005). Effects of hip flexor training on sprint, shuttle run, and vertical jump performance. The Journal of Strength & Conditioning Research, 19(3), 615-621.

2.  Dorn, T. W., Schache, A. G., & Pandy, M. G. (2012). Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance. The Journal of experimental biology, 215(11), 1944-1956.

3.  Webster, K. A., & Gribble, P. A. (2013). A comparison of electromyography of gluteus medius and maximus in subjects with and without chronic ankle instability during two functional exercises. Physical Therapy in Sport, 14(1), 17-22.

4. Bezodis, I. N., Kerwin, D. G., & Salo, A. I. (2008). Lower-limb mechanics during the support phase of maximum-velocity sprint running. Medicine and Science in Sports and Exercise, 40(4), 707.

5. Bezodis, I. N., Salo, A. I., & Kerwin, D. G. (2009). Athlete-specific analyses of leg joint kinetics during maximum velocity sprint running.

6. Schache, A. G., Dorn, T. W., Blanch, P. D., Brown, N. A., & Pandy, M. G. (2012). Mechanics of the human hamstring muscles during sprinting. Med Sci Sports Exerc, 44(4), 647-58.

7. Mann, R. (2011). The mechanics of sprinting and hurdling. CreateSpace.

8. Riley, P. O., Franz, J., Dicharry, J., & Kerrigan, D. C. (2010). Changes in hip joint muscle–tendon lengths with mode of locomotion. Gait & posture, 31(2), 279-283.

9. Brughelli, M., & Cronin, J. (2007). Altering the length-tension relationship with eccentric exercise. Sports Medicine, 37(9), 807-826.

10. Aquino, C. F., Fonseca, S. T., Gonçalves, G. G., Silva, P. L., Ocarino, J. M., & Mancini, M. C. (2010). Stretching versus strength training in lengthened position in subjects with tight hamstring muscles: a randomized controlled trial. Manual therapy, 15(1), 26-31.

11. Guex, K., & Millet, G. P. (2013). Conceptual framework for strengthening exercises to prevent hamstring strains. Sports Medicine, 43(12), 1207-1215.

12. Copaver, K., Hertogh, C., & Hue, O. (2012). The effects of psoas major and lumbar lordosis on hip flexion and sprint performance. Research quarterly for exercise and sport, 83(2), 160-167.

13. Rumpf, M. C., Lockie, R. G., Cronin, J. B., Jalilvand, F., & Street, D. (2015). The effect of different sprint training methods on sprint performance over various distances: a brief review. Journal of strength and conditioning research/National Strength & Conditioning Association.

14. Cronin, J., Ogden, T., Lawton, T., & Brughelli, M. (2007). Does Increasing Maximal Strength Improve Sprint Running Performance?. Strength & Conditioning Journal, 29(3), 86-95.

15. Speirs, D. E., Bennett, M., Finn, C. V., & Turner, A. P. (2015). Unilateral vs Bilateral Squat training for Strength, Sprints and Agility in Academy Rugby Players. Journal of strength and conditioning research/National Strength & Conditioning Association.

16. Holm, D. J., Stålbom, M., Keogh, J. W., & Cronin, J. (2008). Relationship between the kinetics and kinematics of a unilateral horizontal drop jump to sprint performance. The Journal of Strength & Conditioning Research, 22(5), 1589-1596.

17. McCurdy, K., Walker, J., Guerrero, M., & Kutz, M. (2010). The Relationship Between Unilateral And Bilateral Jump Kinematics And Sprint Performance.The Journal of Strength & Conditioning Research, 24, 1.