by Carsten Hoever

Introduction

This is the second part of a series of blog posts about the RunLAB fullbody running analysis offered by the Swedish running shoe company Salming. The first post, which was published on The Running Swede Blog, was mostly a general description of the RunLAB and the general experience. This post will focus more on the technology used in the RunLAB, the biomedical parameters which are captured, and the outcome of my own analysis.

It is usually recommended to attend two RunLAB sessions. The first one will identify aspects of the running form which can be improved. Based on these findings the runner will be given suggestions for form changes or special exercises. The second session is typically a couple of months later to see if improvements in running form have been made. Originally, I planned to write this post after such a second visit. Unfortunately, a recent marathon resulted in acute plantar fascia issues which so far have prevented me from re-visiting the RunLAB. This means that this post has to live without an assessment of whether I have actually improved my running form or not after my initial analysis (but some information about how a friend fared is given at the end of the post). I hope to be able to provide this information in an injury-free future.

Technology

Salming currently has two permanent RunLABs in the Swedish towns of Gothenburg and Stockholm (in the US the technology was also showcased at the  2015 Running Event (more info here).

The basis of Salming’s RunLAB is a treadmill-based motion capture system. The treadmill is a professional grade model from the Swedish company Rodby. The motion capture system is from Qualisys (yet another Swedish company). In the Gothenburg RunLAB this treadmill is located in the centre of the Salming flagship store. On the walls surrounding it, there are eight special high speed motion capture cameras (see Figure 1) which can take images at 400 frames/s. Attached to each camera is a strobe which emits infrared light pulses which are invisible for the human eye but can be detected by the camera. These pulses are reflected by a total of 35 reflecting markers which are attached to the runner’s body at key locations (see Figure 2), usually at “bony” places close to joints, but for example also on the forehead. By combining the two-dimensional images from all eight cameras the motion of all 35 markers in a three-dimensional space can be recreated. With the help of the very high camera frame rate this allows a very precise analysis of full-body motion during running.

Figure 1: One of the high speed cameras.

Figure 1: Markers attached to the runner.

In a post-processing step, this data is then analysed for key biomechanical parameters such as

cadence;
step length;
ground contact time;
flight time;
pelvis height, obliquity, tilt and rotation;
knee angle;
ankle flexion;
foot rotation (pronation, supination), and contact (heel, mid foot, forefoot);
frontal/sagittal ankle path;
shoulder–pelvis flexion, lateral flexion, rotation;
elbow angle, and path;
wrist path; and
contact in relation to centre of gravity.

Figure 3: The RunLAB treadmill in the centre of the Salming flagship store in Gothenburg. While doing the analyses you can actually see a running skeleton of yourself at the big screen in front of you.

Each RunLAB session has the runner being filmed for a couple of minutes at three different speeds which are chosen based on a recent 10k race time (see Figure 3). In addition to the filming, the runner is also critically observed by a trained running coach from Salming’s RunLAB team.

After the results are compiled into sets of animations, pictures and diagrams, the coach goes through all results and explains them to the runner. As a normative reference, the data is also compared to the average results of large number of tested Swedish elite runners. Based on the data analysis, a few key areas in which running form can be improved are identified. This might also involve the runner doing another session of running or doing some other exercises under the scrutiny of the coach.

Before finishing the session, the runner is also given some hints on how to work on the problematic areas. A couple of days after the session the runner receives a link to a detailed web report, see Figure 4 for a screenshot (a full example in Swedish can be found here), which presents all the data in a very descriptive way. More importantly, the web report also contains information about the identified weaknesses and some suggestions for corrective exercises. Note that the layout of the web report will change in the coming weeks; the idea is to align it more with Salming’s so-called Running Wheel philosophy.

Figure 4: Screenshot of the Swedish web report. And yes, they got my name wrong. ;)

My case study

The most insight into the full body running form analysis is probably given by going through the results of an exemplary RunLAB session. In this case my session shall serve as such an example. Due to the extensive nature of the full analysis, it is not possible to go through all recorded parameters in this post. Instead, I will focus on a few parameters which cover the complete range from “totally normal” to “surprising” and finally, and probably most interesting, to “problematic”. In case anyone is interested in seeing my full results, this is the webreport (again unfortunately only in Swedish).

Note: the following images are taken from a PDF version of the report which was provided to me by Salming for the sake of this blog post. The PDF is neither as nice looking nor as informative as the normal web report (see linked examples above) and only includes the raw data and no further analysis, but at least it is in English (which is seen as big advantage for the sake of this post!).

Here are some of the key findings:

Stable, symmetric core motion

We will start with something very boring, a part of my running form which actually is pretty “normal”, the shoulders-pelvis angles for the (lateral) flexion and the rotation. As shown in Figure 5, my results (the blue/green lines) are pretty much in line with the Swedish elite runners results (the grey area). My flexion is probably on the edge of being too high, but not in a way that this is something to worry about. Something we will come back to later is that my shoulder-pelvis rotation is a little bit too small at lift-off.

Figure 5: Results for the different shoulders-pelvis angles. COG is centre of gravity, and LFS and RFS are left and right footstrike, respectively. The blue and green lines are my results for the different speeds, and the grey shaded areas are for the reference. Arrows added by the author for clarification.

Heel striking – Do I or Don’t I???

Popular belief often has it that the root of all running injuries and inefficiencies can be found in two causes related to the feet: (over-)pronation and heel striking. Interestingly enough, there is not only a lot of confusion about the general importance of these features, but also a wrong self-assessment by many runners who put themselves into certain footstrike or pronation-related categories with firm conviction. The RunLAB analysis gives you all the data to finally prove these beliefs…or to shatter them. For the sake of brevity, I will only focus on the footstrike in this post and leave the pronation results out.

I am what some people would call a midfoot striker, i.e. my foot touches the ground more or less flat and simultaneously with both the heel and the forefoot. There is no discussion about this, that’s how it feels when I run and that’s what the wear patterns on my shoes indicate. Only…it is not true, as is shown by the measured floor contact angle in Figure 6.

For both feet initial contact is clearly with the heel, and not even close to an angle at which it could be classified as a midfoot strike (the green area in the plot). People often claim to “get on their toes” at higher speeds, but for me this is not the case: the foot contact angle gets bigger (i.e. I am more dorsiflexing/heelstriking) at higher speeds. There is an interesting asymmetry between my left and right feet: dorsiflexion at footstrike is consistently higher for the left foot, and only at the highest speed for the left one am I getting into a large negative floor contact angle (i.e. larger ankle plantar flexion). I wonder if this is the reason why, when racing, I tend to get hot spots at the tip of my toes, but only on my left foot.

Figure 6: Results for the floor contact angle. LFS and RFS are left and right footstrike, respectively, and SD denotes the standard deviation. The lines are my results for the different speeds, and the colored areas show what classically would be classified as heel striking (blue), midfoot striking (green), and forefoot striking (beige).

So, now that I am officially a heel striker, does that mean that my injury risk is larger? Most certainly not, for this it is for example much more important where my foot hits the ground in relation to the pelvis. Obviously, the RunLAB analysis also includes this data. However, I will spare you the details now (which can be found in the linked web report) – it should be suffice to say that my running form is fine in this regard.

Sitting all day

Above I talked about my relative shoulder-pelvis motion being within the norm. The same is also true for the pelvis obliquity and rotation, see Figure 7. Unfortunately, this is not true for pelvic tilt, where my pelvis is rotated way too much backwards; a very typical trait for people like me who sit too much. This messes up the whole kinetic chain and can lead to inefficiencies and potential issues such as overstriding or problems to get the leg behind the body.

Figure 7: Results for the different pelvis movements. LFS and RFS are left and right footstrike, respectively. The blue and green lines are my results for the different speeds, and the grey shaded areas are for the reference group of Swedish elite runners. For an explanation of the different lines and markers see Figure 5.

As it is often the case, the limited pelvic tilt is only the symptom of a cause which sits somewhere else. Based on his observations of me running on the treadmill and some extra exercises I had to do after the actual RunLAB analysis, Salming’s coach concluded that my limited pelvic tilt is caused by a very stiff upper back. Based on how I feel in my upper back when I do certain movements I am not surprised by this finding. It is, however, quite interesting when you are reminded that a problem which sits rather high up in the body can affect the running form in a substantial way. To increase my upper back flexibility, I received instructions for three special upper body stretches which I should include in the warmup before every run. These have helped considerably to reduce my perceived back stiffness. If this has helped with my pelvic tilt I cannot say right now as it is difficult to judge without an outside observer.

Additionally, my pelvic rotation is too high at toe off. This is the opposite of what was observed for my shoulder-pelvis rotation. This asymmetry means that the pelvis and the upper body are not really working together, leading to an unstable posture.

Excessively static arm motion

The second major critique that I got was that my arm motion is too static. This was partly related to not being relaxed enough in the shoulders and a slightly wrong chest posture. The major issue, however, is the elbow angle shown in Figure 8. Ideally, the angle should be larger when the arms are in the backswing behind the body, and smaller in front of the body. I tend to have a rather constant elbow angle irrespective of where in the swing cycle my arms are. Arm swing can affect the motion of the legs as well, so it is something important to consider.

I was told to be more aware of my elbow angle, especially at higher speeds, and that I should generally try to be more dynamic in my arm swing (but only the sagittal plane, not in the frontal plane, where everything was good). Following this advice, I can clearly say that my stride felt considerably more powerful at higher speeds. At lower speeds, however, I am struggling a little bit to find the right amount of dynamic motion. I very quickly get a little bit too dynamic which then lengthens my stride and lowers my cadence. More importantly, the correct arm motion will also help with getting my chest posture correct, which in turn will help with the position of the pelvis.

Linking things together

So, to sum up, there are actually some things which I need to fix in my running form, and somehow, they all seem to be connected:

· a correct arm swing helps to get a better chest posture and a better leg extension,

· a more flexible upper body is necessary for a better chest posture, and

· a better chest posture leads to a better pelvis posture and is necessary for the pelvis and upper body to work together in a symmetrical and stable way.

· This in turn will help me to have more control at faster paces which should also help me to get off my heels at higher paces.

Figure 8: Results for elbow angle. COG is centre of gravity, and LFS and RFS are left and right footstrike, respectively. The blue and green lines are my results for the different speeds, and the grey shaded areas are for the reference group of Swedish elite runners. For an explanation of the different lines and markers see Figure 5.

Conclusions

This post was my attempt to convey some of the parameters which are measured in a RunLAB session, and, more importantly, how these parameters can be related to more tangible aspects of the running form. I cannot stress enough that the few titbits I provided here are only a small part of the actual analysis. Furthermore, in the way I presented these few examples, there could be the impression that some few key parameters are sufficient for an assessment of a runner’s biomechanics. The reality could not be further from the truth. An assessment of the whole kinetic chain is only possible if the motion of all relevant body parts is considered. This is the great strength of the RunLAB, as it is a true full body running form analysis which looks at the runner literarily from top to bottom. Running dynamics data as delivered by wearable devices such as Garmin’s HRM-Run cheststraps or the RunScribe footpods can be very helpful, but it always only tells a (very small) part of the story.

The captured data is only a part of the reason why a RunLAB session can be such a valuable tool. The more crucial part is the expert coach who analyses and explains the data to the runner. Salming has very wisely decided not to put the data analysis in the hands of ordinary salespersons, but true experts in running biomechanics. The captured data helps the coach to make the right decision, and the visually appealing way in which the data is presented makes the analysis more accessible and more useful for the runner. The data and the coach complement each other in a perfect way: the whole is greater than the sum of its parts.

Regarding the potential benefits of the analysis I would like to bring up the case of my friend Jay, who joined me for the first RunLAB session and recently had his second session. His initial analysis revealed similar shortcomings in arm motion and pelvis position as I have. In his second session he had improved in both of these aspects; he could now could start working on the next area (glute activation) to improve.

Now while I am pretty positive about the RunLAB in general, there are some aspects where I see limitations or problems with the approach. The first, and maybe biggest, it the fact that the test is under “lab conditions” on a treadmill. On average I do less than ten real treadmill runs per year (not counting the few minutes at the running store trying shoes). That doesn’t mean that running on the treadmill is something I struggle with, but each time I step onto a treadmill I also have the sensation that my running form is changing slightly compared to running outdoors. In particular, I have a feeling that I heel strike more. So we have the typical science dilemma here: you are trying to apply findings from an individual lab situation (the treadmill test) to the more general case (running outdoors) which might have slightly different boundary conditions. For most runners this might be of absolutely no relevance, but there might be also other runners who run completely different on a treadmill than they do outdoors. That’s not a problem with RunLAB alone, but basically all tests done on treadmills.

Another aspect is the choice of reference group. Right now they are comparing results against a set of Swedish elite runners. Probably a good assumption as it is likely that someone who runs fast also has a good form (though there are exceptions). Still, an elite runner is also a different beast than your ordinary 30km/week runner. My tempo pace might be an elite’s easy pace, and that can have implications on their and my form at that speed. Now don’t get me wrong, I don’t think there is a generally problem with this particular choice of reference group, but it’s always good to have the context in mind.

Then obviously, the outcome of a RunLAB session might have the runner trying to change their form, with all the potential implications that entails. “If it ain’t broke, don’t fix it” is still a mantra many deem valid with respect to running form as every runner is so uniquely individual in their biomechanics. On the other hand, certain “running form rules” are surely more or less universally applicable: e.g. you will have a hard time finding a runner who benefits from overstriding. Still, there is a risk that a form change might mess up your body in an unexpected way.

I also emphasised that the analysis is nothing without the coach. Right now Salming has experts working with the RunLAB who know their biomechanics and running form and can analyse the data appropriately. This is probably a more important problem for making the technology even more accessible than just the cost of the equipment. You absolutely need to have the right people to work with it. This is probably the biggest reason why we can’t expect RunLABs to open all over the world in the near future.

Finally, to put things into perspective, motion capture analysis of running biomechanics is not really something new. However, Salming can be complimented on making the technology and the expert assessment better available to the general public. The price is not cheap, but reasonable for what you get (at current exchange rates $220 for one session, or $330 for two), and not having to go a special testing facility (like a university lab) for the assessment but just your ordinary local running store certainly also helps.

Disclaimer

The RunLAB session was provided to the author free of charge by Salming Sports AB Sweden.

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.

Colin’s gait footage is interesting because he brought three radically different shoes to the clinic on filming day – a pair of Hokas, a pair of more traditional K-Swiss trainers, and a pair of ultraminimal Vivobarefoot Evos. Colin likes to mix up footwear since he feels it varies the stress applied to the body (an approach I practice myself). He did the run at Kona in the Hokas and loves them, but he still also runs a bit in the more minimal Vivos. Colin doesn’t have a significant lower extremity injury history, so we weren’t trying to fix anything. He’d simply never had his gait filmed before.

Let’s take a look at Colin’s Videos. The first shows his form in side view in the three shoes (Hoka, K-Swiss, Vivobarefoot, in that order):

What’s cool about this video is how remarkably similar his form is in shoes so drastically different as the Hokas and Vivobarefoot Evos. One is maximally cushioned, the other minimally, Colin’s contact pattern is almost identical across the board:

My suspicion is that some people are more sensitive to changes in footwear than others, and Colin has a pretty consistent gait pattern. He also has a decent amount of knee bend at contact and a fairly vertical shin (not much overstride), so he may be running with a stride that doesn’t exhibit a great deal of impact (if he were a significant overstrider in the Hokas I‘d guess his form would look more different in the Evos). He also tends to scuff with his heel at contact rather than coming straight down, and this may allow him to run in the Evos with a mild heel strike. His posture is nice and upright with a slight forward lean. Very nice overall in the side view.

Just for fun, here’s a closeup video of a Hoka footstrike:

The next video is a sequence of the same shoes from behind, focusing in on the feet:

Once again, not a huge amount of difference between the shoes. If anything, the Hokas maybe look a bit more stable than the other two (possibly a consequence of the bucket sole design and wide sole base).

Finally, here are wider shots from the front and back allowing full body visualization:

One of the challenges with gait analysis is that it’s easy to pick out things that look different, but you also have to recognize that everyone moves a little bit differently. Additionally, you need to consider whether the runner is currently injured or not, since sometimes gait patterns you observe are compensations for injury and not necessarily a contributor to an injury. In Colin’s case we have someone who is not injured, and who does not have a significant lower extremity injury history. He’s also performing at a very high level. As such, I’d be very hesitant to suggest any changes to his form, and I try to resist the temptation to overanalyze.

For the most part, I’d say Colin’s form looks great. If there is one thing that gives me a slight bit of concern it’s the fact that he has a lot of thigh adduction during stance. Translated from anatomy-speak into English, this simply means that his thigh angles inward and he has very little space between his knees during swing through. That being said, his shoulders stay pretty level in front and rear views, and I don’t detect a lot of hip drop (should have had him tuck in his shirt). This is a situation where I would leave things alone as I’ve seen cases a lot worse and he doesn’t have a history of injury. However, if problems ever developed at the knee or medial shin this is one thing to possibly have a deeper look at.

It’s always interesting to see how different people move, and Colin is an example of someone who I’d say has very nice form. If you have anything to add, feel free to fire away in the comments!

My buddy Brett Coapland is a chiropractor who specializes in manual therapy and treating athletic injuries, and he also happens to be a pretty competent ultrarunner (11th place overall at the VT 50K this year!). I’d helped Brett out from time to time with gait analyses, and he happened to be looking to expand his practice. He was moving into a new office, and there would be room for me to work out of the clinic if I wanted to, and I jumped at the chance. I’m now working 3 days a week at Performance Health Spine and Sport Therapy doing gait analysis and a bit of coaching, and it’s been a blast so far.

Last week a fellow shoe geek and running blogger stopped by for a visit and a run. I’ve known Sam Winebaum for a long time as a fellow blogger (he writes Sam’s Running, People, Places, and Things), and he often sends me reports from the Outdoor Retailer shows since he spends a lot of time doing consulting work in Utah. I offered to film Sam for fun while he was in town, so we hit the parking lot and shot a bit of video (I do my filming outdoors whenever possible).

Sam is not injured, so this wasn’t a clinical visit. In fact, he just recently finished the St. George Marathon in a time of 3:33. His marathon PR is 2:28 (“many moons ago” as he puts it), and he’s finished in the top 15 at the Mount Washington Road Race on 3 occasions in his life (he was second junior in the race one year!).

We thought it might be fun to share his videos and let you critique them. As I mentioned, he’s not suffering from an injury, but he does feel like his stride has lost a bit of its pop as he’s gotten older. It’s also worth pointing out that he is well aware of his right foot turning out, it stems from a childhood injury that never quite healed properly. He currently is running in Hokas, the adidas Adios Boost, and the adidas Energy Boost.

If you have any form suggestions to help him find his pop, fire away! (I shared my thoughts with him already, but wanted to keep out of it here). Have fun!

Note – these videos are shot at 120fps in HD – you can turn on the HD quality version by adjusting the settings under the little gear icon on the bottom right in the YouTube windows.

Side View

Foot Strike Close-up

Rear View – Whole Body

Rear View – Close-up of Feet

Front View

So what do you think?

For example, last week when I was at the Spaulding Running Center they told me about an iOS app called Level Belt Pro that can measure the alignment of the hips in multiple planes and provide feedback to a runner when they tilt the pelvis excessively in the frontal or sagittal planes (just ordered the belt so I can start playing with it).

As another example, the Garmin Forerunner 620 (should be out in a few weeks at Clever Training) comes with a heart rate monitor containing an accelerometer that claims to measure vertical oscillation of the body, as well as ground contact time (accuracy will be the big question, and there is the issue that the center of mass of the human body is not located near the chest).

Earlier today I received an email from a friend (thanks Bob!) alerting me to an article that DC Rainmaker posted a few days ago about a new foot pod coming from ScribeLabs that is packed with sensors that can measure the position of the foot throughout the gait cycle.

ScribeLabs Motion Sensor – Photo From DC Rainmaker

In particular, the ScribeLabs sensor can measure pitch and roll, with pitch being a measure of foot position in the sagittal plane and roll being a measure of foot position in the frontal plane (an iPhone would presumably be able to do this as well as it’s basically what the Level Belt Pro App does, but it would be tough to attach an iPhone to your shoe!). From a practical standpoint, pitch can tell you the inclination of the foot at contact, which can tell you if you are a heel, midfoot, or forefoot striker. Roll can give you an indication of inversion and eversion during stance, which might help identify movement issues at the ankle. Of possibly even greater interest, the ScribeLabs sensor can provide a measure of peak G-Forces and how those relate to things like stride rate, and also presumably how things change with changes in form and footwear (much like a force treadmill, though again accuracy will be the big question). For someone like me who does gait analyses on a regular basis, tech like this is very intriguing!

I’m very interested in getting my hands on one of these sensors to play around a bit, but looks like we’ll have to wait until next Spring before they are available. Nothing out on price yet, so I may contact the company for more info. In the meantime, head over to DC Rainmaker’s site for a thorough preview of the ScribeLabs Motion Sensor!

As part of the visit, I was able to run on the force treadmill that is a centerpiece of the clinic (they also have a long runway with embedded force plates). I’ve run on force treadmills a few times before, but the nice thing about the Spaulding lab is that it’s set up to provide a simple report for patients that come to the clinic. I thought I’d share my results here.

Just to give a quick overview of what was done, I ran at a relatively easy pace (>10:00/mile) in both shoes (New Balance 1400 v2) and barefoot. While I ran I was able to see my vertical ground reaction force profile on the screen in front of me, which was very cool. It was fun to make the impact peak appear and disappear by forcing a pronounced heel strike. I tried my best to run with my natural gait, which tends to hover around a midfoot strike, though may move backward or forward depending on the shoes on my feet.

Here are the videos and results:

Video – New Balance 1400 v2 Side View

Video – New Balance 1400 v2 Posterior View

Right Foot Results – New Balance 1400 v2

Left Foot Results – New Balance 1400 v2

Video – Barefoot Side View

Video – Barefoot Posterior View

Right Foot Results – Barefoot

Left Foot Results – Barefoot

Some Thoughts

One of the big debates in the running form world lately is whether or not impact peaks or loading rates are a major cause of running injury. The impact peak (see image below) is a rapid initial spike in the vertical ground reaction force (Fz) plot that occurs when the foot initially touches down. It is largely a function of the foot and lower leg making contact and does not reflect the weight of the entire body bearing down yet.

What you’ll notice in my plots (left box in each image) is that the impact peak is small to non-existent in most of them, especially in my left foot barefoot plot. The other three plots typically show a small impact bump. This is typical for a non-heel striking, non-overstriding gait. In the videos you can see that my shin is roughly vertical at contact, and I tend to land midfoot or forefoot most of the time (based on my wear patterns, I’m pretty sure I do heel strike a bit when I run, but not in these videos). In addition to the lack of an impact peak, my vertical loading rates are lower than average. Vertical load rate is essentially the speed at which force is applied to the body at contact. My values range from 38-48 Bw/sec, with the lab average being 75 Bw/sec. Interestingly, the vertical loading rate on my left leg dropped about 8 Bw/s when I took off my shoes, right leg stayed pretty much the same. Not sure why there was a difference.

A couple of other things to note:

1. My cadence computed from my stance and swing times comes out to around 165-170 steps/min. My normal running cadence at a comfortable pace outdoors is around 182-185 steps/min, and since I was running on the treadmill at >10:00/mile pace this seems about right for a pace about 2:00/mile slower than what I typically run (cadence changes with speed).

2. My swing time on the right was consistently shorter than the left, again not sure why or if it matters.

3. My leg stiffness was pretty consistent across the board at 16-17 kN/m, and this is higher than average. Leg stiffness is the ratio of the maximal vertical force to maximal leg compression during stance. So, either my max vertical force is higher than average, or my leg doesn’t compress as much as for other people (I guess I’m not springy). I tend to have a fairly flexed knee at contact, and my guess is that I tend to bend it a bit less after initial contact than average. I’m wondering if my tendency toward higher leg stiffness might explain why I tend to prefer softer shoes?

4. I really have no idea how to interpret medio-lateral or antero-posterior force plots, so if you do I’m happy to hear your thoughts!

So there you have it. I wish the videos captured my waist and trunk movement as I see a lot of people with hip drop issues, and Irene indicated that excessive thigh adduction/hip adduction is one of the biggest risk factors for injury that they deal with and is one of their main targets for gait retraining (along with reducing loading rates). Excessive thigh adduction is typically manifested by the thigh angling inward to a greater degree during stance and minimal space between the knees during swing through.

I’ll end with a brief plug for the Spaulding National Running Center – they are looking for barefoot and minimalist runners (with minimalist meaning most miles in shoes with zero to minimal cushion) to analyze in the lab. If you are in the Boston area and meet these criteria, you might qualify for a run on the force treadmill. They also treat running injuries, so contact them if you are in need!

We’ve all been waiting for data to trickle out regarding actual outcomes from studies that have employed gait modification for the treatment of specific running injuries. Those data are now starting to appear.

A group led by Major Angela Diebal from Keller Army Community Hospital in West Point, NY just released a on-line version of a forthcoming 2012 article in the American Journal of Sports Medicine. The article is titled “Forefoot Running Improves Pain and Disability Associated With Chronic Exertional Compartment Syndrome.”

Chronic exertional compartment syndrome (CECS) is a condition that primarily affects active people (about 69% of those diagnosed are runners), and is characterized by swelling of affected tissues. There are four separate muscle compartments in the lower limb, of which the anterior compartment is most frequently affected in compartment syndrome. The connective tissues that encapsulate these muscle compartments do not stretch much, and thus excessive swelling in these compartments can lead to diminished blood flow to the affected tissues, as well as compression of nerves leading to pain.

Diebal et al. indicate that accepted belief as to the cause of compartment syndrome is “that exercise increases intramuscular pressure, which in turn compromises circulation, prohibits muscular function, and causes pain and disability in the lower leg.” They go on to state that “As the problematic exertional activity (typically running) continues, compartment pressures incrementally increase, which presumably causes increasing lower leg pain, sensory abnormalities, and muscle weakness, eventually resulting in a premature cessation of the activity.”

The Mayo Clinic website reports that “Conservative treatments typically don’t help with chronic exertional compartment syndrome. However, surgery is usually successful, allowing you — whether you’re a recreational or serious athlete — to return to your sport.” The surgery mentioned is known as a fasciotomy, and involves cutting the connective tissue sheaths surrounding the swollen compartment to reduce intracompartmental pressure (fair warning – if you have a strong stomach, you can see gruesome photos of this surgery here). Surgery can successfully treat the condition, but side effects are possible, recovery time can be extensive, and lets face it, if you can avoid having your leg sliced open that’s probably not a bad thing.

Thus, the goal of this study was to determine whether an alteration in running gait could serve as an effective, and more conservative, alternative to surgery for the treatment of CECS. Previous research suggests that ankle position can influence intracompartmental pressure (ICP) in the anterior compartment (e.g., forefoot running decreases anterior compartment pressure, and ankle dorsiflexion increases ICP in the anterior compartment). Furthermore, the authors report that forefoot running has been shown to reduce eccentric activity in the tibialis anterior muscle (eccentric contraction is that which occurs while the muscle is lengthening, such as during the post heel-strike foot slap).

The tibialis anterior, shown in red in the image to the left (image via Gray’s Anatomy and Wikipedia), is the major dorsiflexor of the ankle and is found on the front, outer portion of your shin (it is the largest muscle of the anterior compartment; other muscles in the compartment include those that extend your toes upward). The idea is that by having patients with CECS adopt a forefoot striking running style, they would reduce pressure in the anterior compartment where this muscle is located, reduce eccentric activity in this muscle, and thereby reduce pain and disability associated with the condition.

The researchers recruited ten patients with CECS who were candidates for surgical intervention (as determined by an orthopaedic surgeon) – all were physically fit members of the military, and all had experienced symptoms for at least six months. Furthermore, all were confirmed as heel strikers, and pain onset occurred with less than five minutes of running.

After taking a battery of pre-intervention measurements {e.g., ICP, ground reaction forces, step length and rate, 2-mile run time, run distance before severe pain onset (up to 5km) etc.}, the subjects went through a training program to instruct them to forefoot strike with an increased cadence (3 steps per second, 180 steps/min). They also performed a variety of drills taught by the POSE method of running, and did some barefoot running and were cued to “run quietly.” Training sessions occurred 3 times per week for 6 weeks (45 minutes each session).

After the six week training period, the subjects went through a repeat battery of tests to determine the effect of the change in running gait. More interestingly, the researchers also did a minimum one-year follow-up with each patient to determine if the intervention had lasting success. Here’s what they found:

1. Intracompartmenal pressure (ICP) increased significantly from resting levels after a running bout prior to the intervention. After the gait retraining, ICP did not increase from resting after a running bout (see graph below from Diebal et al., 2012, American Journal of Sports Medicine).

2. Running distance prior to severe pain onset (up to 5km) increased significantly post-intervention, and pain reported on a visual analog scale while running decreased significantly post-intervention (see graph below from Diebal et al., 2012, American Journal of Sports Medicine):

3. Step length, contact time, peak vertical ground reaction force, impulse, and weight acceptance rate all decreased significantly post-intervention. Step rate increased significantly.

4. At the one-year follow-up, 8 of the 10 patients reported that they were running a minimum of 5 km two to three times per week. The two exceptions were due to a torn ACL suffered while playing soccer, and a sprained ankle – neither of these individuals reported running limitations prior to the subsequent injuries. Mean 2-mile run times were significantly faster at the one-year follow-up.

5. All patients reported that they were able to participate in sports without limitation following the intervention.

6. Perhaps most importantly, none of the patients required a fasciotomy.

The results of this study are striking in that they are so uniformly positive, which somewhat overcomes the limitation of a small sample size and lack of a control group. For a condition that typically requires surgical intervention, to have ten individuals who were candidates for surgical intervention avoid surgery and return to normal activity levels as a result of modifying their gait is a very encouraging result. In fact, all but one of the ten individuals were able to complete the entire 5km run test with virtually no pain after the six-week intervention period, and follow-up after a year indicated that any changes that occurred during the intervention were retained long-term. I’m always hesitant to call anything a “cure,” but it’s hard to argue with these results.

The strength of these results suggests that gait modification could become a first-line treatment in the management of anterior compartment syndrome, and suggests that surgery need not be the fate to which sufferers of this painful condition must succumb.

It is also encouraging that these patients appear not to have experienced negative outcomes from the gait modification – altering foot strike and other aspects of stride can have unintended consequences, and it’s important to keep this in mind when applying an intervention such as this. For example, another study that looked at the effects of forefoot striking (via POSE technique) found increased power absorption and eccentric work at the ankle in POSE runners, but that study stipulated that runners not let the heel touch the ground (almost all runners I have observed let the heel touch down after initial forefoot contact). Given the mix of methods employed in the current study (cadence training, POSE drills, barefoot running), it’s hard to know exactly what the resulting form changes looked like. Nonetheless, we don’t want to simply trade compartment syndrome for Achilles tendinopathy or a metatarsal stress fracture, and it is encouraging that this appears not to have happened.

One of the reasons why this study is so gratifying is that it shows that applying biomechanical knowledge of the running gait to a particular injury can lead to a promising new therapeutic intervention. We know that heel striking increases pressure in the anterior compartment and probably works the tibialis anterior harder relative to forefoot striking. Thus, it makes logical sense that avoiding a heel strike might reduce symptoms associated with CECS and possibly “cure” the condition – it would appear that this is exactly what happened. What we don’t know for certain is whether a similar intervention might work for other conditions where the link between biomechanics and pathology is less clear. We also don’t know for certain which aspect of the running form change is responsible for these positive outcomes – was it the forefoot strike, or perhaps the reduced stride length or increased cadence that had the biggest effect. Hopefully future studies will attempt to tease this apart.

To end, I’ll note that a few months ago I listened to a British Journal of Sports Medicine podcast interview with Dr. Andrew Franklyn-Miller – he also reports success of gait retraining for the treatment of compartment syndrome, so we may really be onto something here…

The second clip shows Bolt jogging along a track during what appears to be a post-sprint cool-down. Gait is quite different, and he appears to now bring the heel down after landing on his forefoot, and in some cases he may be landing flat. However, he’s clearly not overstriding and mashing his heels into the ground just because he’s running slowly!

Typically, the results of the wet test are interpreted as follows. If no distinct arch is visible, you have flat feet, probably overpronate, and thus need motion control. If there is a distinct dry area under the inner side of the arch region of your foot with a complete wet band adjacent to it on the outer side, you have normal arches, normal pronation, and would do fine with a mild stability or perhaps a neutral shoe. If the outer wet band is separated in the middle by a dry area, or if the wet band is very narrow, you have high arches, underpronate, and need a neutral cushioned shoe. This 2004 article from Runner’s World website provides a typical example (with diagrams) of how to interpret your “wet test” results.

Unfortunately, there’s a big, big problem with the wet test, and it’s due to the fact that the test is done when you are standing still. This is what’s known as a static measure of arch height/deformation/collapse, meaning we take it while we are not moving. Though we all might feel like we are standing still sometimes when we run, I can assure you that running involves movement of your legs and feet, and we don’t need a scientific study to prove that! When we run, forces generated are very different than when standing still, and the arch of the foot behaves differently. Why? Because the arch is not simply a passive structure. There are muscles that help to support the arch, such as the tibialis posterior and the flexor hallucis brevis, and it’s quite likely that they are going to be more active when you are running than when you are standing still.

Several scientific studies have shown that static measures of arch height yield significantly different results than those measured while walking or running (dynamic activities). In a study published in Clinical Biomechanics in 1989, Dr. Joseph Hamill and colleagues from the University of Massachusetts compared static and dynamic (walking) footprints using a measure called arch index. To determine arch index, they applied ink to the feet of their subjects, had them walk over sheets of paper, and compared the size of the ink imprint in the region of the midfoot relative to the overall area of the foot imprint (excluding the toes – the shaded region in the picture at left shows the midfoot area compared by Hamill et al., 1989).

Hamill and colleagues found that arch index (size of the shaded area) increased in seven subjects, decreased in 15 subjects, and did not change in two when they compared the walking footprints to the standing footprints. Though static and dynamic measures were strongly correlated in this case, they were found to be significantly different, with the arch tending to be higher when walking than when standing. They suggest that differing orientations of the lower leg, increased weight bearing, or increased activity of foot musculature could explain the differences observed. They also found little correlation between observed arch index and other dynamic aspects of gait, writing that “the lack of significant findings between the dynamic aspects of gait and arch index may discount the use of this measure in functional lower extremity evaluation.” Furthermore, they write that “Although a large contact area may be present, very little force may be exerted over much of the contact area. A person who has a very large arch index may actually demonstrate a pressure distribution pattern more closely resembling a person with a very high arched foot (small arch index).” Finally, the authors do indicate that “first ray mobility was particularly effective in predicting dynamic function, supporting its continued use as a measurement in lower extremity evaluation.” So, the take home message seems to be that footprint type isn’t all that useful when it comes to predicting walking gait, but mobility of the first metatarsal and big toe are very important.

Jay Dicharry and colleagues from the University of Virginia published a paper in 2009 in the Journal of Orthopaedic and Sports Physical Therapy in which they did a bit more elaborate assessment of static arch deformation vs. dynamic  arch deformation during walking and running. They did this by comparing values obtained from a static functional navicular drop test (see image below for navicular location), a static subtalar navicular drop test, and measures obtained by 3-D video analysis of arch height during gait (using markers placed on the foot).

Bony structure of the medial longitudinal arch of the foot – navicular bone is located near the apex of the arch – Photo from Gray’s Anatomy via Wikipedia

The functional navicular drop test sounds complex, but in reality is quite simple. The navicular is a bone in the midfoot near the apex of the medial arch, and the functional navicular drop test compares the height of the navicular during relaxed seated (non-weight bearing) vs. relaxed standing (weight bearing) positions. Higher values for functional navicular drop would thus indicate a greater degree of arch deformation/collapse, and thus a floppier, more mobile foot. Lower values for functional navicular drop indicate a more rigid arch that does not compress much. The second static test – the static subtalar navicular drop test – compares navicular height when the foot is placed in “neutral” position to when the foot is allowed to relax and compress the arch.

Results of Dicharry’s study (see below) showed that despite significant differences in arch collapse between the groups during static testing, arch collapse was identical in all three groups during walking, and the only difference observed during running was a small but significant difference between the hypermobile and hypomobile groups, neither of which were significantly different from people categorized as neutral (i.e., only the extremes were different, and the magnitude of the difference was far smaller than would be found using the static measures). Furthermore, despite increase in force magnitude during running, only the hypermobile group exhibited greater arch compression during running as compared to walking. They suggest that neuromuscular control during dynamic movement could explain these differences – basically, the brain activates appropriate musculature in the foot and legs to manage the forces and maintain the arch during walking and running, and this is not captured by measuring the arch when we stand still. The basic message is that even if you have flat feet and your arches collapse when you stand still, your arch may behave very much like the foot of a normal arched person when you are walking or running, likely due to muscular control.

This brings us to paper number three, which was just published on-line in Gait & Posture. The authors, led by Jesper Bencke from Copenhagen University Hospital in Denmark, compared measures of static navicular drop to both 2-D and 3-D measures of arch deformation during walking. They found only a moderate correlation between static measures of the arch and those obtained during walking (r² = 0.31 for you stats oriented folks), and conclude the following:

“Assuming the foot as a two-segment structure in the sagittal plane with a hinge joint placed at the navicular bone between the forefoot and the hindfoot, the increased plantarflexor moment during push-off would correlate to an external moment attempting to dorsiflex the forefoot with respect to the hindfoot. The lack of good correlation between static and dynamic measures could thus be a result of this extra load being counteracted differently between participants. This would further imply that a static test measuring the ND (navicular drop) might only have limited validity as predictor of MLAD (medial longitudinal arch deformation) during gait.”

And these are not the only three papers that have shown this – if you’d like to read the full text of one you can take a look at Deng et al., 2010, who found no relationship between navicular drop measurements and arch deformation measured during walking.

So what does all of this mean? Basically, it tells us that what the arch looks like and how it deforms when we are standing or sitting probably doesn’t tell us much about what the arch does when we are actually moving. Thus, applying the “wet footprint” test as a basis for determining foot type, and thus as a basis for choosing a running shoe makes very little sense. If you are in a shoe store and they suggest that you try this test or if they take a look at your arch while you are stationary, be very wary of any advice that you get (this probably applies to those fancy foot scanning machines as well). As Dicharry showed, only the extreme floppy and rigid feet differed in degree of arch deformation during running, and the difference was very small and of unknown clinical significance (and neither differed from so-called “neutral” feet). What’s more, we have several studies showing that assigning shoes based upon arch height provides no benefit in terms of injury outcomes when compared to simply assigning everybody a stability shoe regardless of foot type (see here and here for examples).

All of this does not mean that some individuals with extremely rigid or mobile feet might not benefit from some tailored shoe advice, as studies do suggest that individuals with extremely flat or rigid arches do seem to suffer different types of injuries. However, it does suggest that the wet-footprint test as a general tool for assigning shoes should be put to rest. At the very least, methods that provide clinically relevant measures of arch deformation dynamically and simply and without a requirement for expensive gait analysis equipment that is rarely found in a shoe store should be investigated (e.g., the 2-D method described by Bencke et al.).

Having run in the Go Runs myself, albeit not Meb’s custom version, I was curious to see if Meb’s stride had indeed changed. Luckily, elvin314 on YouTube captured a clip of Meb in slow motion from last Sunday, so I was able to take a look. Below are videos, in the following order, of Meb from NYC 2011, NYC 2010, and Boston 2010.

Below are some stills showing Meb at the moment of foot contact in the three races, once again in order from NYC 2011, NYC 2010, and Boston 2010.:

It’s hard to know for sure exactly if any differences observed might be due to his new footwear, but it does appear that although he is heel striking in all three, his 2011 heel strike does look a tad less pronounced. It should be noted that these videos provide nothing even close to a controlled comparison. I have no idea if he was running the same speed in all three videos, where on the course the NYC videos were taken, and the Boston video is from an area of the course with a slight downhill grade. 

Just for kicks, I tallied up some stride timing data from the three videos for you to take a look at (most values below are averages from 2 consecutive steps). Again, not a controlled comparison at all, but interesting to ponder:

What do you think, has Meb’s shoe change made a difference, or are the data above just variation about his mean due to the individual circumstances where each video was taken?

Note – he kind of does a stop and start thing here as he’s egged on by big brother – the last bit provides the best view. Enjoy!

One of the points I consistently try to make here on Runblogger is that runners are highly variable. Even among elites, form is variable, as I attempted to point out in a post on gait variability in elites at the 2011 Boston Marathon (and also in this post on the 2010 Boston Marathon). As such, I don’t believe there is a one-size fits all “ideal” running form, nor do I think there will ever be one footwear option that will be best for all runners. I do believe that we evolved to run barefoot, and that barefoot is the human default, but some of us are so far removed from ancestral anatomy and physiology that running barefoot or in a barefoot-style shoe might not be a good solution. Genetics, history of past footwear use, dietary habits, and history of past physical activity (most of us didn’t grow up running 10k barefoot to school each day!) all conspire to make us the variable species that we are.

I’m constantly reminded of variability when I write shoe reviews. A shoe that I find too firm might be a favorite of a friend, and a shoe that I find plenty wide might be too tight for someone else. Any shoe review that I write is from my perspective, and should be considered with this in mind. What works for me may not work for you, and vice versa.

Another reminder about human variability comes when I read the scientific literature on running biomechanics. Non-systematic results are commonplace, meaning that different people respond in different ways to a given intervention (whether it be footwear type, a stride change, etc.). For the remainder of this post I want to give an example of variability that I think really emphasizes this point quite well.

Yesterday I was reading an article by Clarke et al. from a 1983 issue of the International Journal of Sports Medicine. The title of the article is “Effects of Shoe Cushioning Upon Ground Reaction Forces in Running.”

In a nutshell, the authors were attempting to determine the effects that running shoes of varying midsole hardness have on the forces that the body has to deal with during the stance phase of running. They had 10 runners run across a force plate a number of times in shoes with very firm and very soft midsoles (pace was 6 min/mile), and then compared the results between the two types of shoe – the goal was to compare extremes along the spectrum from firm to soft shoes since that would be expected to result in the maximum difference between the two conditions.

Before we dig into the results, here’s a quick reminder of what a vertical ground reaction force plot looks like for a heel-toe runner:

On the vertical (Y) axis is the value of the vertical ground reaction force as a function of body weight. You can think of this as how much force the ground is applying vertically through your foot as you run. The horizontal (X) axis shows time in milliseconds. The curve depicted on the graph shows how vertical GRF changes from the point of initial contact of the foot with the ground (time 0) to the point where the foot leaves the ground on toe-off (about 300 ms in this example). What you’ll notice in this graph is that there are two distinct force peaks. First, the impact peak is the initial force applied to the foot by the ground at initial heel contact (remember, this graph is for a heel-toe runner). Full body weight is not being applied at this point, so the impact peak is basically a function of the weight of the foot and lower leg hitting the ground. The active peak represents the force applied by the foot and supported body weight during roughly mid-stance. Notice that it is larger than the impact peak – this is the typical pattern.

Clarke et. al (1983) measured the height of the vertical impact peak, the time it took to reach the vertical impact peak (which gives info about how fast the impact force was applied), the height of the active peak, as well as a few other gait variables. Keeping in mind that the shoes being compared were at opposite extremes of the firmness spectrum, the results were quite interesting. First, and somewhat surprisingly, they found no significant difference in the height of the impact peak between the two shoes. In other words, the magnitude of the impact force was the same on average whether a runner was wearing a soft shoe or a firm shoe. The time it took to reach the impact peak was found to differ, with the softer shoe delaying the impact peak by about 4 milliseconds on average (this means that the softer shoe tended to slow the application of the impact force, which is probably a good thing). Third, they found that the active peak (they refer to it as the propulsive peak) was significantly higher on average in the softer shoe.

In summary, just looking at the average results, softer, cushier shoes do not appear to reduce the impact force, but they do slow down the rate at which the force is applied to the body (much as a boxing glove would slow the rate at which impact is applied to your hand if you punched a brick wall). Softer shoes also result in higher forces at mid-stance – the authors suspect this might be related to greater heel penetration into the midsole during stance, allowing the calf muscles to exert greater propulsive force under the forefoot on pushoff (if the heel sinks into the misdole under pressure, it is effectively decreasing the heel-forefoot drop).

These results, particularly regarding impact force, seem somewhat counterintuitive – runners generally believe that greater cushioning will reduce the magnitude of the impact force, and heavy runners are often directed to maximally cushioned shoes for this very reason. But, this ignores the fact that our body is pretty darned intelligent, and our legs adapt their stiffness to the conditions underfoot (read this post for more on leg stiffness in running). Thus, when running in a firm shoe, our knees tend to flex more than they do when we run in a soft shoe – by changing properties of the midsole all we do is shift cushioning from one place to another (underfoot to say the knee joint), and the magnitude of the impact force stays the same.

What’s really interesting about this study is when you look at the individual results, which are quite variable. Two individuals exhibited no impact peak at all, and their results thus were not included in the impact comparisons (the authors speculated that they were midfoot strikers). Here are the results the individuals (forces are measured in units of body weight):

When you look at these results at the level of the individual, it becomes clear that responses are somewhat variable. In particular, if you look at the results for impact force peak in subjects 4 and 5, they exhibit completely opposite responses to the two shoes. Subject 4 impacts considerable harder in the hard shoe, but subject 5 impacts considerably harder in the soft shoe. So, although the mean impact response between the two shoes was not significantly different, suggesting that midsole hardness need not be a consideration when it comes to managing impact force, for these two individuals it matters a great deal. What’s more, if we assume that lessening impact force is a good thing (this point is debatable as impact can stimulate bone growth, and we have no idea what threshold limits for impact might be problematic for any given individual), these two runners would require completely different types of shoes! Going even further along this line of reasoning, if our goal was to provide a shoe for these runners to reduce impact, the conventional wisdom is that more cushioning is the way to go – but, that would be the wrong answer for 50% of the runners examined here who had higher impact peaks in the softer shoes. This is what gets lost when looking at mean responses – they don’t tell you what is best on an individual level.

You can see the same type of thing when you scan the other columns. Soft shoes generally do seem to delay impact peak, but not in 100% of cases, and in some individuals the difference is very small between the two shoes. Soft shoes seem to result in a higher active peak, but again, sometimes the difference is quite small.

The point I’m trying to really emphasize here is that runners are variable, and we each have different needs on an individual level. This is why I have such a problem with the traditional approach to running shoe design. Why in the world should we expect that every individual will do best in a shoe with a 10-12mm heel-forefoot offset??? Until recently, this is the only type of shoe that has been available to most runners (and don’t say flats have always been around – they have, but generally in specialty stores and were typically not recommended for long distances and only for “efficient” runners). As recently as January of this year, I went into my local Dick’s Sporting Goods and counted 90+ running shoes on the wall – all of them – every single one – had a traditional offset. No a single racing flat or more minimalist shoe was to be found. That has changed in the past six months, but we are still a long way from really understanding how best to assign the best shoe to an individual runner. Same goes for assigning shoes based on arch height, pronation, etc. We have no strong evidence that this approach works, and in fact there is evidence that assigning shoes based on foot type is no better than assigning a stability shoe to everybody. This doesn’t mean that the approach doesn’t work for some individuals, just perhaps that it shouldn’t form the primary basis upon which we assign shoes.

We need a lot more research on how to do a better job at all of this – how to tinker with form when needed or to leave things alone, how to determine who needs lots of cushion and who doesn’t, who needs a more stable platform and who doesn’t, who’s better off ditching shoes altogether? It’s a difficult task to be sure, and right now the best approach I can suggest is a willingness to self-experiment. I do believe form and shoes play a big role in healthy running, and I don’t think that runners need fear trying different types of shoes if they do it carefully. My hope is that as more people tell their individual stories, and as more research comes to light, better advice will come with time.