- Know who you are assessing
Far too often those that conduct movement assessments do so with a “one-approach fits all” mentality. This can be misleading and inappropriate at times. Remember that youth under the age of 16 are still maturing and the motor development process is still occurring. Conversely, a 30-year-old has fully matured physiologically and their motor development has been completed. Now on the other side of the spectrum, a 42 year old overweight, sedentary individual wanting to change their lifestyle habits is going to have a completely different need for movement.
What I am getting at here is that a young athlete will have strategies or deficits in their movements as they are still developing, whereas an adult should have their basic or fundamental movement patterns established. When you implement a squat, your intention for performing the protocol will be different on the basis of age, motor development, and demand for movement. For those working with athletes under 18 years of age, the Long-Term Athletic Development Process is a great review of the development process for motor development and physical skill acquisition.
- Know the objective of the assessment
Again, just because you were taught to identify particular things (mobility, strategies, stability, etc…), it does not mean that is where the assessment stops. Keep in mind that many of the movement protocols you will have your athlete/client put through, are new, challenging, and unlearned. One of the biggest mistakes with movement assessments is that it is assumed that the athlete knows exactly what it is that you expect of them in the protocol; it is also assumed that the instruction on how to perform the protocol is sufficient enough for the athlete to remember and then mimic what it is you want them to do. The objective initially, should be to demonstrate the ability to apply the instruction of a protocol by the athlete and then assess the movement. This is called fast learning where changes or adaptations in an unfamiliar movement are produced to give a reasonable movement the athlete feels confident with for you to assess. True learning of a movement, particularly a new or unfamiliar one, requires nearly 3 weeks before it becomes automatic. It can take longer for others. Therefore, if you do not account for the stage of development and the familiarity of the movement, what are you assessing?
- Consistency, consistency, consistency
For those healthcare practitioners, you understand from your medical or physical evaluations that in order for a response (positive or negative finding) to be relatively true or valid, the response should be evident on other tests of different variations. Many orthopaedic tests algorithms are now showing support for multiple tests to confirm pathology over a single isolated test. Movement assessments are no different. If you identify a problem (strategy, lack of mobility, lack of control, etc…) then it should be evident in other protocols that are assessing similar things. For example, if a 2-legged squat identifies knee valgus that may be attributed to lack of motor control of the medial hamstring complex in the first 30 degrees of descent, then a 1-legged squat should also elicit the same findings in order to conclude that the knee valgus in the first 30 degrees of a squat is in part attributed to the poor motor control of the medial hamstring complex.
Avoid using single protocols or tests to assess a region. Use 2-3 if you can to ensure consistency of your findings, otherwise bias sets in and you could be correcting or neglecting an issue inappropriately.
- Stability 101
If you speak to a biomechanist and seek the definition of stability you will probably get something along the lines of “in the presence of a perturbation a characteristic behavioural response occurs”. Therefore, in order to assess the stability system, in this case the human body, it must be challenged either by gravity with body weight based protocols or through the application of an external load (barbell, resistance bands). There is a spectrum of stability that needs to be discussed. First is structure stability – this is the ability of passive elements (ligament, joint capsule) to maintain the neutral zone of the joint through motion either during an orthopaedic examination or athletic movement. Second, is static stability – this form of stability requires an interplay between the nervous system, musculoskeletal system, and osseo-ligamentous system. The expectation for static stability is that at the joint or anatomical region no movement occurs when challenged (gravity or external force). For example, the ability to hold a prone plank without moving for the duration of the test protocol. The third type is called asymptotic stability. This form of stability indicates that when the system is challenged, the change in position of the joint or anatomical region is imperceptible to the naked eye and looks stationary during a static or dynamic positioning. An example would be the patella remaining in line with the web of the first-second rays during a single legged squat. This form of stability is typically what movement assessment protocols are attempting to identify. The last form of stability is the bounding or dynamic stability. This form of stability suggests that upon a challenge (movement) there is a change in the position and motor behaviour about the joint or anatomical region which permits movement (forward, change in direction, reverse, etc.).
Static stability, asymptotic, and dynamic stability all require control to produce stability. This is highly contextual, meaning that it depends on the demand of the movement and competence of the athlete performing the movement. To generally state a movement looks stable is an overgeneralization that qualitatively one cannot determine. Biomechanical laboratories determine and quantify stability. The reason for this is that there is a paradox between mobility and stability. The more mobility a joint or anatomical region needs to be, the less stability that said joint or anatomical region becomes. Conversely, the more stabile a joint or anatomical region needs to be, the less mobile it has to be to produce a movement. The contribution between how mobile and stabile a movement is not a qualitative process and requires highly sophisticated instrumentation to determine.
You can make inferences about stability all you want, but the true nature of what you can assess in the movement is control of the region or joint through the identification of postural deviations, joint misalignments, and a lack of control to execute the movement competently.
As I had mentioned above in the stability 101 section, control is the more relevant component of what you assess in movement. Control is a function of the efficient interplay between the nervous system and the rest of the body (muscle, joint, ligament, etc.). There are two forms of control that need to be discussed here. The first is motor control. This control is the ability of the athlete to produce a contraction type: concentric, eccentric, and or isometric. The contraction type is contextual and based on the demand of the movement. Typically this is where isolated examination of a joint or anatomical region is conducted. The other form of control is movement control. This form of control entails the athlete’s ability to follow the instructions and the protocol to the specifications of the assessor. These specifications include tempo of movement, depth or desired end point, and sequencing of joints to produce a movement. This last form of control is influenced on the learning capability and the ability of the athlete to follow or mimic instructions.
Without control (motor and movement), stability is an irrelevant component of the movement assessment that does not have context for interpretation. Stability requires a functioning motor system first before stability can be determined. Therefore, control of a movement provides greater context to the issues at hand. Stability becomes highly relevant in the biomechanical laboratory, not when assessing athletes in the clinic.