Kinematic continuum or conundrum? The need for threshold sensitive, multi-task testing
A recent study (Marshall et al., 2015) goes some way to highlight both the benefits and potential pitfalls of reliance on video analysis to identify risk in athletes’ movement. The paper presented what could be considered as a kinematic continuum, revealing the biomechanical similarities and differences existent between a single leg squat (SLS), a 30cm depth drop and a cutting manoeuvre. Predictably, kinematic data varied most markedly between the slow, sagittal plane biased SLS and the tri-planar, high velocity cut. As landing and cutting actions often fall under the ‘high risk movement patterns’ classification, the authors conclude the SLS is highly suspect in its ability to reveal injury risk. This interpretation of the outcomes of the study could be seen to support the need to employ movement control testing at both low and high threshold, at multiple regions and in multiple planes. Certainly, The Performance Matrix would whole heartedly support an approach demanding a finer resolution of movement quality to be revealed rather than a reliance upon one solitary test. However, a closer look is warranted to both this study and video analysis.
Pain, performance, control; what are we testing?
As the study’s athletes were already in pain, the omission of pain free athletes raises unasked questions of comparison to a non-symptomatic group. As pain can change movement characteristics (Hodges & Tucker, 2011), an inter-group comparison may have revealed even greater distinctions in performance. As for cognitive control differences between groups, just like Beckham, we will never know. If this quality had been checked and a control group included the study may well have further informed on how pain free does not always equate to good control (Mottram et al., 2009).
Points of view; take a cautious perspective
A word of caution is also required for the reader seeking to make sense of the data often presented following video analysis. The Marshall et al, (2015) study’s data is representative of biomechanical vectors and moments as measured from the location of a camera and should not be perceived as measures of the degree of hip rotation with reference to the athlete’s pelvis. This point highlights one of the concerns with interpretation of data originating from this method. Looking at the forces and vectors of ordinary movement patterns allows delineation of their specific biomechanical ‘footprint’, yet assessment of cognitive control requires something more. Comerford underlines the point; ’within The Performance Matrix tests we consider the ability to control certain components of movement (e.g. control or limit as much as possible tibial external rotation or hip medial rotation). The requirement to control a specific component whilst staying within a particular trajectory of motion is a more sensitive way to evaluate if hip internal rotation or knee valgus is controlled.
It didn’t change; no, it already has
Video observation of a SLS may not demonstrate any change in alignment if the test is initiated with the hip already internally rotated and remains there during hip and knee flexion. This could be mistakenly seen as the athlete possessing desired dynamic alignment of the hip in this plane.
Additionally, due to its interactive nature, The Performance Matrix testing process offers individuals the chance to correct the suspected impairment; is this poor control of just a lack of clarity in testing? If the athlete merely switches to another uncontrolled pattern both deficits are revealed allowing further analysis and mediation. Video, without this interactive process, cannot offer such information or rigour.
Beware ‘literal specificity’
The Marshall paper may raise concerns over what any one single test may reveal. Certainly cutting actions and a SLS are clearly very different yet, dismissal of the latter’s risk profiling utility raises issues. Taken to its ‘nth’ degree, literal specificity would state, ‘as injury often happens during cutting, landing and change of direction, there is only the need to test these movements.’ Such a stance would be reminiscent of the ‘functional’ versus ‘non-functional’, dead-end conversations that have plagued and hindered movement control retraining over the past decade. Cognitive testing and retraining of the movement system is not quite such a blatant process as joining the dots between kinematic markers of mechanism and any one test. One point to upset the specificity applecart is how poor movement quality at a low intensity has also been seen to carry injury risk at high (Roussel et al., 2008). A broader, interactive and integrated consideration of the factors involved is to be championed for managing movement and risk. The SLS provides such an example.
The value of single tests
Poor control of hip flexion, as often seen in a SLS, typically represents deficits in the ability to efficiently employ the gluteals, a pattern associated with excessive contributions from the hamstrings. If the hamstrings are to be employed for high velocity, phasic decelerations and time sensitive translation control of the tibia (ala ACL protection) their increased involvement at low threshold is neuro-physiologically and architecturally unwelcome. Therefore, the SLS may be informative of injury mechanisms during drop landing and cutting actions.
In contrast to a video analysis methodology, Botha et al, (2014) considered small knee bend (SKB) performance in junior, field based sport athletes with unilateral hip pain and femoro-acetabular impingement. Their investigation revealed deficits in low threshold, cognitive movement control on both the pain affected and asymptomatic side. As a result the authors propose the presence of pain may have a bilateral effect on movement quality and/or that movement quality itself predisposes the athlete to injury occurrence. Additionally, the paper identifies alterations in movement are not regionalised to the locality of pain.
What a single test can’t show
If both the neurophysiology and biomechanical properties of movement control are to be fully questioned, both must be represented across a spectrum of tests. Recently, inter & intra tester reliability has been shown for such a multi-test tool (Mischiati et al., 2015). During this process (The Performance Matrix) participants will sometimes display good control at high intensity but poor control at low. Of note, no matter how ‘strong’ or ‘enduring’ the individual, testing can often prove cognitively exhausting as the athlete is asked to perform what they can’t, as their movement blind spots are revealed. If we adopted the ‘literal specificity’ approach, performance of only high velocity landing or change of direction tasks would leave those risks apparent in low threshold environments unchecked.
High risk strategy or high risk ability?
Comerford expands on the deficits of one test screening, identifying the need for a battery of tests, ‘we consider the athlete’s risk as low if hip internal rotation only presents in one type of challenge situation. The risk is considered higher if the same movement fault presents in multiple loading planes. This is one excellent reason why we use low and high threshold testing. Also, during both low and high threshold tests we us sagittal, coronal (lateral landing or lateral hop -like cutting) and axial loading (rotate during the landing or hopping action) with the instruction to cognitively control the alignment and displacement of multiple joints. One test cannot do this, no matter whether it is biomechanically similar to injury mechanisms or not.
Fast forward; strategy change?
Rather than passive observation of ‘high risk movement strategies’ perhaps there is the need for the literature to increasingly migrate towards discussion of ‘high/low risk movement ability’. This provision would further support testing of movement quality as opposed to simple observation of purported risk related movement. Video analysis is an excellent tool. For one, it comes into its own when revealing the evolution of a high velocity injury event, as pause, rewind, etc… furnish the viewer with almost unlimited options on what happened and when. If preventing the injury is the goal, and mitigation of risk is a key purpose of movement analysis kinematic data alone will fail reveal the control component. If we do not ask the question we will struggle to see the answer no matter how many tests we perform or how expensive the technology employed.
- Botha, N., Warner, M., Gimpel, M., Mottram, S., Comerford, M., & Stokes, M. (2014). Movement Patterns during a Small Knee Bend Test in Academy Footballers with Femoroacetabular Impingement (FAI). Working Papers in the Health Sciences 1:10 Winter 2014 ISSN 2051-6266 / 20140056. http://www.southampton.ac.uk/assets/centresresearch/documents/wphs/NBMovement%20Patterns%20during%20a%20Small%20Knee.pdf
- Hodges, P. W. & Tucker, K. (2011). Moving Differently In Pain: A New Theory To Explain The Adaptation To Pain. Pain. 152, 90-8. doi: 10.1016/j.pain.2010.10.020. http://www.ncbi.nlm.nih.gov/pubmed/21087823
- Marshall, B., Franklyn-Miller, A., Mealey, E., Strike, S., Gore, S., Shoenfeld, J., Moran, K., & Falvey, E. (2015). Can A Single Leg Squat Screen Provide An Insight Into Neuromuscular Control During A Single Leg Drop Landing And A Running Cut. ISBS- Conference Proceedings Archive. https://ojs.ub.uni-konstanz.de/cpa/article/view/5957
- Mischiati, C. R., Comerford, M., Gosford, E., Swart, J., Ewings, S., Botha, N., & Mottram, S. L. (2015). Intra and Inter-Rater Reliability of Screening for Movement Impairments: Movement Control Tests from The Foundation Matrix. Journal of Sports Science & Medicine, 14(2), 427–440. http://www.jssm.org/research.php?id=jssm-14-427.xml
- Mottram, S., Warner, M., Chappell, P., Morrissey, D., & Stokes, M. (2009). Impaired Control Of Scapular Rotation During A Clinical Dissociation Test In People With A History Of Shoulder Pain. 3rd International Conference on Movement Dysfunction Edinburgh, UK, 30 October – 1 November.
- Roussel, N. A., Nijs, J., Mottram, S., Van Moorsel, A., Truijen, S., Stassijns, G. (2008). Altered Lumbopelvic Movement Control But Not Generalised Joint Hypermobility Is Associated With Increased Injury In Dancers. A Prospective Study. Manual Therapy. doi:10.1016/j. math.2008 http://www.manualtherapyjournal.com/article/S1356-689X(08)00197-5/abstract