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THOUGHTS ON OUTDOOR GAIT ANALYSIS

SCIENCE

THOUGHTS ON OUTDOOR GAIT ANALYSIS

As I stand right now I firmly believe that the most valid method for assessing running form, gait and biomechanics is to perform an evaluation where the subject is running outside on their normal trails on a routine type of training workout they would normally run. Over the past 5 years I have witnessed first hand varying levels of gait analysis performed in a wide range of training centers, labs and clinics around the world and not once have I ever left the facility feeling truly satisfied. As a professional running coach who combines a rigorous scientific background and a real life experience-based pragmatic approach I am by default always striving for ways to make athletic training and testing protocols more specific and ultimately more relevant.

the most valid assessment is performed when the running is outside

I was introduced to the development of wearable technology for sports four and a half years ago when I first began testing prototype products for Garmin (then Dynastream). In the last 3 years I have supported numerous kickstarter style projects, some of which have folded, some of which have been moderately successful and some that have grown and grown. Observing all of these companies has taught me how to tell the difference between products that are too niche and frankly just unnecessary and products that add real value (in a digital world that is prone to being flooded with more and more ‘so what?’ data). It has also enabled me to monitor the progress of some companies that are being truly innovative and forging ahead into the future.

When I conduct a gait analysis I am trying to better understand two critical areas 1) what is the runner’s current risk of injury and 2) what is the runner’s current level of mechanical efficiency. Of these it is injury prediction and prevention that commonly garners the most attention and for good reason. The less injury downtime a runner has, the more consistently they can train and the better their long term athletic development. Because of this focus on assessing injury risk the gait analysis must collect enough accurate and reliable data to enable the practitioner to make a valid, evidence based judgement. However in my experience, from what I have observed, it is extremely rare that this is the case.

Some classic issues I have seen in gait analysis:

  • The practitioner does not take adequate time to learn the subjects background (medical history, injury history, line of work, habits, pressures and stresses etc)
  • The subject only runs on the treadmill at one intensity/pace
  • The subject only runs at comfortable/easy pace
  • The subject does not run for long enough to become fatigued
  • The practitioner does not test the subjects muscle strength or joint mobility
  • The practitioner does not test the subject’s neuromuscular activation and motor control, even their proprioceptive feedback systems.
  • The practitioner does not directly measure and record quantitative data

Some of these problems are a failure in the general approach to the task and others a failure in the specific execution. Both inevitably lead to an inferior analysis.

So what is it that I’m looking for in a ‘technically superior’ gait analysis?

Firstly I want the subject to run in the true environment that they use whether it be their local park, their favorite streets or a field or athletics track. I want to test them on the surfaces they commonly use with the inherent mechanical stiffness of that surface and all its smooth or uneven challenges to the subjects proprioceptive systems.

true environment

Secondly I want the runner to incorporate different paces and gradients during the workout. I have interpreted numerous runners’ biomechanics where I have observed that dysfunctions only occur when the runner specifically runs uphill, downhill or at particular paces. If this is the case with a given subject then my only hope as an evaluator of understanding this ‘hidden’ issue is to ensure the subject is challenged in a wide variety of ways.

variety of challenge

This is the reason why I have seen so many runners over the past 4 years, participate in a gait analysis session only to be sidelined by an injury later that was not predicted at all by the results of the analysis. This is also the reason why when I perform a running evaluation I include a gps heart rate monitoring device on the subject. That way I can later partition the data based on sections of heart rate (cardiac work rate), of pace, of uphill/downhill/flat or even sections of similar terrain (ie. gravel road section vs muddy single track section).

Thirdly I want to integrate complementary assessment methods that add further evidence to the running evaluation in order to build a complete and coherent picture of the subject’s movement competency. This includes testing the subjects muscle strength (force generation), muscle activation (ability to contract muscles quickly and independently), range of motion and running specific functional movement (variation on the common FMS).

changes in gradient

Some of the questions I am trying to answer with this are: what is the subjects level of independent control over specific muscles, how quick can they turn certain muscles on, what level of force can they generate from key muscle groups, what range of motion do they have across key joints, what level of postural control do they have, how effectively can they use proprioceptive feedback and so on.

During these tests just as I do with the running evaluation I record bilateral values and compare measured values from the left side and right side of the body (and in some cases between anterior and posterior muscle groups). Consistent with accepted methodology in athletic testing I categorise the left to right side differences as:

  • 0-5% green light (no immediate action required)
  • 5-10% amber light (corrective exercise program required)
  • 10+% red light (stop or limit running and corrective exercise program required)

Data measured during the running evaluation is also similarly subjected to this left to right side comparison. In this case the measured data can comprise values of:

Ground contact time, ground reaction force, bulk power, peak tibial acceleration, foot deviation angle, foot rate of deviation, leg spring stiffness, foot strike pattern, postural control and pelvic control as well as the basic metrics of cadence, pace, heart rate and elevation profile.

Finally I want the subject to be significantly challenged in some way (requires integration with the subjects training plan if they have one). This can either be with elevation changes or fast paced running. Of all the areas of gait analysis this is the one I get most animated about. At comfortable intensity runners can often hide and mask dysfunctions using learned and reinforced compensation patterns. However from experience as a former elite athlete and as a coach I know that when the subject is challenged and becomes significantly fatigued they exhibit reflexive intuitive behavior.

variety of challenge

When instinct begins to take over inside the subject there exists a short lived but fantastic opportunity to understand just how the subject intuitively responds. This is the point when we observe the first break down in form but also the first response go-to self protection and compensation method of the body. When the subject has a subtle but important in-built tendency to favor one muscle group or one side in order to get the job done, this is when we illuminate that go-to behavior. If I was to just simply have the subject run for 3-5min at easy pace on a treadmill in a clinic I would have no chance of ever getting this insight. Believe me, this is a critical point.

It is because of this inclusion of additional challenge into the assessment that I believe hand on heart, that this form of evaluation is better in predicting root cause issues and helping runners keep injuries at ‘arm’s length’ over long periods. Often when I am wearing my coaching hat and looking at data from a sustained or challenging run I will go to look at the last 5min of the data file first. It’s at this point in the data that I know I will find interesting patterns that tell me how the runner deals with challenge and fatigue. In contrast the first 5min of data will often only serve to highlight the expected effect of delayed neuromuscular ‘switch-on’ as the body gets prep’d (warmed-up).

delayed neuromuscular switch on

Before closing there is one further subject to incorporate into the discussion, that of the psycho-biological model (a term coined by Prof Sam Marcora) or more simply how perceptions in the conscious brain can affect movement performance in athletic activity. When a subject runs on an unfamiliar treadmill in a ‘benign’ indoor environment the visual cortex of the brain does not receive the signals indicating forward movement that it would when running in the natural environment outside. There are no trees, buildings or fence posts moving past the runner and hence no perception of speed.

In fact on the treadmill the runner isn’t moving through space at all, the wall ahead of them stays the same distance away throughout. Essentially the process that the runner would normally through outside of monitoring their surroundings and adjusting pace or gait in response to what they see simply does not happen.

On the subject of psychology and conscious perception and its effect on patterns of motor control one other aspect of outdoor gait analysis that I like is that once the runner begins the session they are quickly out of sight of the practitioner. And at this point we have to ask the question: how many runners can jump on a treadmill in a clinic and not consciously make minor adjustments to their form knowing that they are in the immediate presence of an ‘expert’ whose job it is to watch and monitor them?

Society teaches most of us to react in some way to this style of close quarter human interaction. On a lengthy run during an outdoor gait analysis session the subject is not watched over in any way. I often find that the runner has forgotten after 5min that they are even collecting data for future analysis. In some cases if the runner regularly performs their workouts in a group then they will also run the gait analysis session for me in that group. This again reinforces the realistic nature of the approach and again allows the runner to forget that they are taking part in an analysis.

realistic nature of the approach

So summarised here are some key points relating to why I believe so much in outdoor based running gait analysis with wearable sensors. I believe that assessment of the runner’s gait has an opportunity to move away from the clinic or lab and into the space between coaching and medical assessment in way that will deliver results that are more practical, applied and ultimately more realistic. Because of this I feel this type of assessment will be performed better by practitioners who have a deep understanding not just in natural science, physiology and biomechanics but also in coaching runners on a regular basis as well as in the development and testing of wearable technology.

M.Sc, MSci, B.Sc, CSCS, NSCA-CPT, XPS, CGS. Malc Kent is a professional coach, internationally respected applied scientist and former world class athlete. His services include sports coaching and mentoring, workplace coaching and biomechanics coaching.

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