What are you really assessing with a biomechanical assessment?

Biomechanical assessments are everywhere. We can get them for back pain, foot pain, our running gait. The list is endless.

The question we have to ask is what are we assessing when we look at someone’s biomechanics?


For a start biomechanical analysis is often performed on people already in pain to find out what ‘dysfunctions’ or ‘anomalies ‘ they have that could be causing the pain to occur. How do we know that the increased or decreased kinematics that arises after analysis is not the result of pain rather than the cause of it? The assumption is often it is the cause, one that relies on a Cartesian tissue stress/nociceptive/bottom up driven model of pain.

Protective motor responses may mean that biomechanical changes are a defense of the nervous system rather than a defect of the anatomy. Over time this may form a behaviour that has nothing to do with structure but a learned habit to avoid what the body sees as a potential harmful situation.

We seem to have disassociated our mechanics from the desire to perform an action and all the factors that are associated with the implementation of a movement.

Our mechanics are a reflection of our intent, our fears, our previous movement experiences including our successes and failures and often our pain. They have meaning and consequence.

Why do we expect people to move freely into a position that is or has caused them pain in the recent past? How do we know they did not move differently before the pain started? An objective marker in this situation would be great but often not realistic for someone new to you. What data are we measuring them against that indicate what ‘normal’ is? With large anatomical individuality why would we see movement that is homogenous? Have a look at a bunch of people running next to each other in any health club to see the large variation in movement present.

We have some loose kinematic risk factors but no real way of working out causation to the problem at hand, especially if they are chronic in nature. We know tissue state and pain become increasingly less correlated in this circumstance. That does not mean that they cannot be associated but not in the predictable and reliable way we sometimes like to propose. What is happening on the inside in terms of bone movement or muscle activation is, outside of the lab, a (potentially informed) guess. Any attempt at certainty and prediction is simply arrogance.

As we are starting to separate pain from a solely anatomical origin we should start to separate movement solely from anatomy or anatomical potential.

Lets imagine for one second we are on the final tee of the US open or Wimbledon or my personal favourite the world cup final. The physical biomechanics of the swing, serve or kick are the same as they were in an earlier round or in training when we could execute with freedom. Suddenly under pressure our ability to implement the same mechanics becomes infinitely harder. The only thing that has changed is the context. We are not using different equipment, playing on a different surface or with a strange ball. The stress of achieving our goals, desires and fear of failure could and often does have detrimental effects on our biomechanics. Think Adam Scott a few years ago at the British open when he blew a big lead after playing a fantastic 68 out of 72 holes. Implementing our mechanics with all the stress hormones running our round our blood stream is evidently not that easy!

The same might be true of moving in a confined space. We are aware of our surrounding environment. Ever ducked when going under a height restriction in your car or squeezed in when going through width restrictions? Our peripersonal Space is the space within reach of any limb of an individual. Our pericutaneous Space is the space just outside our bodies but which might be near to touching it. Our environment might modify our movement planning before we have even realised our mechanics into movement.

The same maybe true of a skill we have never performed. This may not be a reflection of our structure or mechanics but a reflection of never having performed that particular skill before. Ever seen someone walk on a treadmill who has never done so before? It certainly does not usually look like the way they walk normally so what would we get from assessing the mechanics of this skill they have never performed? The same is true of rigid screening systems that define what good movement should look like. I never overhead squat. Why would I be any good at it? It maybe my lack of skill you are assessing not my anatomy or mechanics. Assess me after some practice or with an understanding of how to score higher at the test and I maybe a lot better. If you are going to test my movement it should be a relevant skill that I use regularly. It may not be that my muscles are tight or weak. Muscle activity like skill execution is probably context related through motor pattern implementation in a given scenario.

Changes in someone’s response to performing a movement could even give us clues to what is about to be played out. Sweating, stiffening, holding breath, flushing, hesitation and facial tension all maybe responses to the perceived threat level of a biomechanical assessment.

How do people feel about moving after we have labelled their biomechanics dysfunctional, abnormal or potentially harmful? How does that drive movement behaviour in the future? Are you assessing another practitioner’s poor choice of language with your biomechanical exam?

All this does not mean looking at movement is bad or pointless. Instead we have to think about the meaning AND the mechanics to better understand movement and the many factors that may influence it. We must also be prepared to accept that what we are seeing is not always relevant with so many factors affecting the pain experience.