Movement Signature of the Gravity Intolerant Runner – The Importance of Swing Phase

Ryan Hall – 2010 Boston Marathon

This is a guest post by Dr. Jeff Moreno, DPT

A common observation  in the world of running is the runner that overstrides. I think whether you are in the world of research, or treating runners full-time in a clinical setting, we can all agree that overstriding is suboptimal. We all understand the potential physical implications of this suboptimal running form, and its affect on running economy. What is currently up for discussion is the root cause of overstriding and other less than desirable running forms.

Injury rate in runners has been reported to be as high as 80% in a given year. This is excessive and significant enough to warrant research funding from private and federal organizations. This funding has, and is, allowing for more and more research to be done in the areas of shoe design, foot strike patterns, barefoot running, stride frequency, and understanding the etiology of common lower extremity pathologies found in our runners. We have already learned invaluable information regarding stride length, stride rate, shoes, ground reaction forces (GRF’s), and the effects of biofeedback on running form. The research has provided clinicians with new approaches to treatment that have been easily applied to our runners with some success in reducing pain and allowing for a return to running. However, are we still missing the bigger picture, and if so what next?

My purpose for writing this article is to describe what I am seeing clinically as a physical therapist on a daily basis as I treat runners. The focus of this post is to not only discuss what is being researched currently or what the latest studies tell us, but to give you a clinical perspective that may help us start bridging the gap between the research lab, the clinic, and more importantly on the track/road. With that said, I hope that this will initiate conversation and interest, and that it leads us to look at suboptimal running form and more importantly poor movement patterns and muscular imbalances as part of a greater dysfunction.

If you are still reading, I am writing to you, the researcher and clinician, studying and treating runners on a regular basis. Since you frequently work with these athletes, I am going to assume that you have a background education in biomechanics and analytical anatomy. My only other request is that you have an open mind, and allow yourself to think outside the parameters of what we know the current research in running has shown us.

So with that said, when observing and assessing a runner at any level, I look first at very basic and simple fundamental movements that assess how the running athlete’s brain represents movement from point “A” to point “B”. I am not going to talk about my specific assessment; however, it is important to understand that when I am assessing and/or treating a runner I am really looking at the specific subconscious and involuntary movement that is produced by the brain. The last thing that I do is put them on the table, and this is only to confirm clinically what I saw dynamically during their movement tests and while running. After I have assessed how their brain represents movement, I look at the runner’s ability to resist/control the affects of gravity and then overcome gravity over distance, time, and desired speed. The ability to control and overcome gravity during running requires very specific coordinated patterns of movement with specific timing. Frans Bosch and Ronald Klomp in their book, Running: Biomechanics & Exercises Physiology In Practice, describe running as being cyclical in nature. As stated by Bosch and Klomp (2005), “This means that a previous movement will have a great influence on the following movement. The motor system needs information obtained from the previous step [swing] before taking the next step [initial contact/loading]. The body is geared to copy patterns of motion continuously [good or bad]” (p. 132). In other words, the action of the swing leg will dictate that of the stance leg (and vise versa). Both motions are unconsciously and involuntarily related (e.g., motor program, Central Pattern Generator; optimal or suboptimal). Therefore, running has been described as a contralateral pattern like that of crawling/walking with the opposite arm and leg moving together in a coordinated fashion to ultimately produce forward motion.

For those of you treating runners, the depth and breadth of your understanding of normal movement and gait needs to be very high in order to truly understand abnormal movement/gait. The more you observe the walking/running gait the more you start to pick up the subtleties of gait. The Frans Bosch “method”, recently summed up by Jeff Cubos, DC, on effective coaching and performance therapy, suggested one should consider the following:

-Know what you see
-Know what you don’t see
-Know why you don’t see what you don’t see
-Know how to best get what you want to see
– …so that you can see it consistently

Therefore, looking at the walking and running gait globally as a series of optimal or less than optimal patterns, I believe, is extremely important and often overlooked during gait analysis. Current research and our understanding of causative biomechanics has given us specific invaluable information on less than optimal movement during initial contact and loading phase during running (e.g., hip adduction, pelvic drop, tibial rotations etc…). However, if running is truly cyclical and dependent on the phase prior, then the swing phase just prior to initial contact and the contralateral stance phase is just as important as the loading phase. If this is so, which I believe to be true, why then is all our current research focused primarily on one small piece of the pattern? Yes, I understand that loading rates and higher impact peaks due to suboptimal loading can be a cause for some of our most common running injuries, but I think it is time to move on and step outside the box (speaking to the researcher). I see these stance phase injuries as a product of a greater dysfunction that cannot be explained only by what is happening at the time of the visual dysfunction, but as a byproduct of a poor global pattern. This has allowed me to assess runners through a different lens and not only treat the products of a poor loading phase (e.g., weak glutes), but also treat the patterns of movement that led to the poor timing and motor control of the glute during stance phase.

Everybody, I believe, has a unique kinetic signature during running that can make an individual’s gait unique to themselves. However, there are also very important coordinated patterns of movement that must occur during the running gait. I come from the world of distance running, and like all distance runners, I think sprinters are a special breed! With that said, some of the best minds in coaching/running come from the world of sprinting, and if you have spent any time on the track and have listened to and read what these great coaches (Dan Pfaff, Tom Tellez, Irving “Boo” Schexnayder, Loren Segrave, Ralph Mann, etc…) have to say you would realize quickly that they spend a significant amount of time on developing a highly skillful athlete.

When looking at sprinters versus distance runners, I see very defined patterns of motion in sprinters that are much more consistent across individuals than in distance runners. Sprinters have an amazing ability, due to training and biomechanical/kinesiological demands, to achieve triple flexion during swing (hip flexion/abduction/external rotation, knee flexion, ankle dorsiflexion) and triple extension during propulsion (hip extension/internal rotation, knee extension, ankle plantar flexion). The flexion and extension patterns in runners and sprinters are always cyclical and require high levels of coordination and timing. These triple flexion and extension patterns are obviously accentuated in the sprinter versus the distance runner as seen above; however, the pattern should always be expressed in any runner regardless of speed or talent.

Now, understanding that running is highly coordinated and cyclical, I want to present what I am seeing clinically. I have had the privilege and opportunity to treat runners of all levels from Olympians to recreational runners. Working with these runners, whether injured or not, I am seeing very distinct patterns regardless of the level of ability and talent. Currently, in the world of running if you ask anybody regularly treating runners at any level what is the most important motion that a runner should possess, they will most likely say hip extension. I believe that hip extension is extremely valuable and needed to coordinate movement appropriately during running; however, in the clinic I only truly find a significant loss of monoarticular (iliopsoas) hip extension necessary to run approximately 25% of the time. Most runners, I have come to believe, have the ability to extend their hips, whether they take advantage of their available hip extension is another story. (By the way, most of the force that we produce whether running or sprinting occurs from initial contact to mid-stance at which point force decreases rapidly – a little off topic but something to think about). With that said, I do often find a significant restriction of the biarticular hip muscle rectus femoris. Does the short and/or stiff biarticular hip flexor and knee extensor (rectus femoris) result from overuse? Absolutely! I believe significant overuse of this two-joint hip flexor, along with the TFL (tensor fasciae latae), is resulting from the poor ability to control gravity and coordinate movement. These two muscles are primarily active during mid swing and at the end of swing to mid-stance. Why is this occurring? I will try to explain.

What I am seeing clinically is not poor hip extension, but just the opposite, poor hip flexion, and the ability to coordinate hip flexion appropriately with hip abduction and external rotation (triple flexion) at the same time during all movement, not just running. So, if I had to group the most common pattern of impairments that I am seeing in my distance runners, it would be as follows: swayback posture, thoracic kyphosis (stiff), forward head, poor abdominal control/coordination, poor hip stability, long and weak iliopsoas, stiff rectus femoris/TFL, knee hyperextension, relative plantar flexion in standing, forefoot varus, and poor intrinsic foot strength (see picture for example). When running, these impairments listed above often result in poor outcomes like overstriding, abductory twists (tibial rotations/whips), crossover effects, pelvic asymmetries, femoral rotations, posterior center of mass (COM), lower extremity pendulum effects, etc. I see this postural dysfunction in all levels of athletes from elite to recreational. These same runners, when asked to perform simple fundamental patterns of movement like a squat (i.e., triple flexion), single leg balance, step down, quadruped rock back, etc… struggle and often can’t coordinate very basic patterns of movement that are necessary for walking let alone running. How many of your runners when squatting or single leg squatting can easily disassociate their hip from their pelvis/spine and move their hip independently with ease like a highly skilled runner would? These athletes will express the same poor pattern of limited hip flexion and excess hip adduction and internal rotation regardless of the movement asked to be performed. Now, given that the human body is efficient and always moves first toward the path of least resistance, the body chooses these patterns of movement subconsciously/involuntary to be more efficient. This has forced me to try and answer what is driving these suboptimal movement patterns that have become hardwired motor programs in our runners?

A good example of this dysfunctional pattern is the runner that was described above with swayback posture and a long and weak iliopsoas and stiff rectus femoris. This runner will have a poor ability to triple flex due to insufficient passive and active kinetic energy from the anterior hip muscles (poor elastic recoil) resulting in an altered triple flexion pattern. The weak and long iliopsoas and dominant biarticular rectus femoris muscle will prevent sufficient hip flexion in swing, and will most often result in excess knee extension during the end of the swing phase to advance the lower extremity (see picture above). Therefore, we cannot expect the contralateral lower extremity to function in a coordinated fashion due to the cyclical nature of the running gait. The pattern becomes altered and instead of hip flexion/abduction/external rotation, knee flexion, and ankle dorsiflexion (triple flexion pattern), the runner displays excess knee extension with hip adduction at the end of swing to advance the lower extremity (rectus femoris/TFL dominance). Fifty percent of my patients will complain of knee pain with this type of gait, but you can imagine the other potential biomechanical implications during the loading phase that can be produced due to this poor coordination of gait.

If you are a skeptic, test this for yourself. Go outside right now and run with high knees or up a steep hill (to accentuate hip flexion) and ask yourself what happened to your knee during mid to late swing prior to initial contact, as well as, the reactivity of your hamstring prior to initial contact. Now, go run while limiting hip flexion, and ask yourself what happens to your knee motion at the end of swing and during initial contact. You will have noticed that when accentuating hip flexion it is almost impossible to create excess knee extension during the end of swing to initial contact; however, when limiting hip flexion you will have noticed immediate excess knee extension and possible overstriding in order to advance the lower extremity. What you just performed was outside of your voluntary control and part of a global pattern; one optimal verses the other suboptimal. Remember, these two patterns that you just performed are global and coordinated (see pictures above and below of less than optimal versus optimal triple flexion respectively)! The limited hip flexion with subsequent overuse of the rectus femoris to advance the lower extremity can inevitably result in the base of support (BOS) being significantly in front of the COM, leading to larger loading rates and impact peaks. I am seeing these abnormal patterns of movement expressed clinically regardless of strike pattern, shoe type, speed, flexibility, strength, and even in the presence of a stable trunk. I think all of us treating runners on a daily basis would agree that it is not all about the “shoe”, but more what the running athlete puts into the shoe!

As a side note, to those clinicians that have spent time in a neurological rehabilitation setting treating stroke or traumatic brain injury patients, you will probably recognize that pattern of gait when limiting hip flexion. These patients express significant limitation in active hip flexion (depending on the affected area of the brain), which ultimately produces knee hyperextension, ankle plantar flexion, and subsequent circumduction of the lower extremity to advance limb forward during gait. This is due to a cerebral vascular accident or traumatic brain injury resulting in hemiparesis. I am not saying that these runners have had a CVA or TBI, but from a neuromuscular perspective they demonstrate similar patterns of movement globally speaking (you neurological buffs, something to think about).

I first wrote about this pattern two years ago and there was very little interest within the running community, but a recent study in the Journal of Biomechanics by Noehren’s group out of the University of Kentucky has been published which may shed some light on the possible importance of hip flexion in reducing loading rates and impact peaks during running. Many studies have been published looking at forces and loading rates contributing to overuse injuries in runners. The goal of this recent study was to look at different variables that may predict magnitude of impact peak and loading rates, as well as how different knee and hip muscles during swing affects these loading forces. The results suggested increased hip flexor activity and higher positioned thigh during mid swing decreases velocity of the leg at landing leading to smaller forces at impact (Thank You Noehren’s group for studying something other than differences in shod vs unshod runners!).

If we look at this from a biomechanical and kinesiological perspective, what effect does hip flexion during the swing phase have on muscle activation of the hip extensors and knee flexors prior to contact? Understanding that running is cyclical, what happens during swing can and does affect loading phase. Preparatory muscle activity during mid to late swing in recent studies has been shown to be important in the role of foot-ground contact. This preparatory muscle activation enhances the control of muscles during the subsequent loading phase, leading to better lower extremity muscular stiffness. This is accomplished by the facilitation of the gluteus maximus and hamstrings (and others); due to proper triple flexion during swing, to prepare the lower extremity for ground contact. Clinically, I am seeing a lack of passive and active kinetic energy during swing hip flexion at a runner’s preferred speed. I believe this is limiting the preparatory gluteus maximus and hamstring activation ultimately resulting in excess knee extension during late swing and the potential for higher forces at impact. To all those in the research lab, what would be interesting is to look back through all of your past data amassed on those fancy treadmills and force plates, and see if there is a correlation between those that have less hip flexion and more knee extension during end of swing/initial contact in those that overstride and those that don’t at a constant speed.

Now to the question, why is this combo of swayback posture, thoracic kyphosis (stiff), forward head, poor abdominal control/coordination, poor hip stability, long and weak iliopsoas, stiff rectus femoris/TFL, knee hyperextension, relative plantar flexion in standing, forefoot varus, poor intrinsic foot strength, and the subsequent lack of dissociated hip flexion so common? Well, let me tell you, this leads me to my final observation and area of interest. Culturally, we are very different in the US versus other non-industrialized nations. As a culture, the United States and other western cultures have seen a significant increase in postural related dysfunctions from the head to toe. We, as a society have lost our ability to resist the affects of gravity in all weight bearing activities, let alone running with 2.5 to 3.0 times body weight while on one leg. I have defined this as the gravity intolerant runner. Knowing that we are culturally intolerant to the forces of gravity due to pervasive inactivity and prolonged sitting; I believe that this evolution of our structure and function has resulted in suboptimal patterns of movement during running. Those distinct patterns that are seen in our running patients/clients of swayback posture, posterior COM, stiff rectus/TFL, knee hyperextension, ankle plantar flexion, and forefoot varus position, I believe, are a result of our cultural intolerance to gravity. As a result of this pervasive global intolerance to gravity, the running athlete’s perception of normal posture has been altered resulting in significant neuro-musculoskeletal imbalances leading to many of the impairments commonly related to most running injuries. As a culture we have developed talent in the absence of skilled coordinated movement.

How do we overcome this? Let’s get our runners, coaches, and health professionals to understand that developing talent starts with developing the skill of movement and postural tolerance to gravity. Let’s take our knowledge of causative biomechanics and kinesiology and apply it to correcting altered patterns of movement that are contributing to all the impairments that we see in our every day runners. More importantly if we really want to reduce running-related injuries in the future let’s first start by asking our youth to go outside and run, jump, climb, push, pull, roll, and even fall to naturally increase postural tolerance to gravity!

My challenge to all those do running-related research and those treating runners are:
1. Look globally!
2. Understand that to run efficiently the runner had better resist/control and overcome gravity well!
3. Understand that running is a series of coordinated patterns of movement that require proper timing.
4. Look at running cyclically and know that what is happening in stance is dictated by what the swing leg is doing and vise versa.
5. The human body is highly adaptable which means that the human body can unfortunately be efficiently inefficient!
6. Swing phase is just as important (IN MY MIND MORE IMPORTANT), than stance phase when it comes to running related injuries.
7. How much are you looking at swing phase influencing what happens at stance phase with your injured runners? Are you treating patterns of movement or just parts of the pattern (e.g., pelvic drop, weak glutes)?
8. Can we please start bridging the gap between the track/road and the research lab. In order for this to occur that would require some of our brightest minds in the lab to start speaking with the coaches primarily working with these athletes (In A Perfect World).
9. Can we please move on from the shod versus unshod debate, PLEASE!!! There is so much more going on globally with the running athlete than just what is happening at the foot/ground interface.

Let’s start discussing!

Jeff Moreno, DPT, OCS
Precision Sports Performance Running

References
1. Bosch, F., Klomp, R. (2005). Running: Biomechanics & Exercise Physiology Applied in Practice. Philadelphia, PA: Elsevier.
2. Chumanov, E., Wille, C., Michalski, M., Heiderscheit, B. (2012). Changes in muscle activation patterns when running step rate is increased. Gait & Posture, 231-235.
3. Dietz, V. (2002). Review: Proprioception and Locomotor Disorders. Neuroscience, 3, 781-790.
4. Frank, C., Kobesova, A., Kolar, P. (2013). Dynamic Neuromuscular Stabilization & Sports Rehabilitation. International Journal of Sports Physical Therapy, 8 (1), 62-73.
5. Kyrolainen, H., Belli, A., Komi, PV. (2001) Biomechanical factors affecting running economy. Medicine Science Sports Exercise, 33(8), 1330–1337.
6. Novacheck, T. Biomchanics of Running. (1998) Gait & Posture, 7, 77-95.
7. Saunders, P., Pyne, D., Telford, R., Hawley, J. (2004). Factors affecting running economy in Trained Distance Runners. Sports Medicine, 34 (7), 465-485.
8. Schmitz, A., Pohl, M., Woods, K., Noehren, B. (In Press). Variables during swing associated with decreased impact peak and loading rate in running. Journal of Biomechanics.
9. Weyand, P., Sternlight, D., Bellizzi, M., Wright, S. (2000). Fast top running speeds are achieved with greater ground forces not more rapid leg movements. Journal of Applied Physiology, 89, 1991-1999.

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