Functional Testing: myths, benefits and relevance for sports performance

Functional test in sports are a group of tests which are regularly used by physiotherapists in trying to assess one’s readiness to participate in a given sport modality or to establish a baseline measurement, such as in a pre-season screening or at the start of a rehabilitation program. Consequently, it allows the physiotherapist to track one’s progress and / or assist in return to play decisions. It can also serve the purpose of identifying specific movement faults, muscle weakness, imbalances, all of which can form a diagnosis based on functional performance rather than structural pathology.

Dynamic Valgus Mechanism ‘step down test’

For instance, the dynamic valgus mechanism during ‘step down test’ has been highlighted as a predictive factor to knee injuries. Good trunk, pelvis and hip stability seem to be necessary for good knee kinematics. It is a myth, however, to assume all dynamic valgus movement patterns are a solely resultant of gluteal weakness. Even though gluteal strength is of ultimate importance for functional performance, motor control impairments, foot control and others can also be causative factors behind a dynamic valgus mechanism of movement.

Furthermore, it is important to mention that the literature points out dynamic valgus to be more prevalent in female than male soccer players, which places the females at a greater risk of having and ACL injury than their counterpart males. When considering the chances of a second ACL tear following the first reconstruction, both males and females are equally at risk if a dynamic valgus is present.

Other examples of functional tests routinely used by physiotherapists in order to identify a dynamic valgus mechanism are single leg squat, single leg hop, Star Excursion Balance Test (SEBT) and more.

Star Excursion Balance Test

Another good example of functional testing is the use of the Star Excursion Balance Test or the Y-balance test to assess those with Chronic Ankle Instability (CAI).  In many research papers related to chronic ankle instability, these tests are used as benchmark, or outcome measures, in determining the effects of a given intervention. Others have used them as part of the neuromuscular training program targeting this population.

As per common characteristic, functional tests involve complex moments which often require participation of multiple joints and muscles simultaneously, just like in real life scenarios. For instance, in the SEBT, participants are required to balance on one foot whilst reaching with the other foot in 8 different directions. Kicking a ball during soccer, pivoting on one foot playing basketball or reaching out in order to get to a long tennis ball are all examples of complex movements in sports. Those movements will require good postural dynamic control and that is what a SEBT or Y-balance test try to measure, one’s ability to control his body in space whilst balancing in one foot.  It is important to mention that there are other factors that could affect one’s ability to balance, such as neurological or vestibular problems. There are specific tests developed for that purpose which are beyond the scope of this blog. Moreover, to assume that a functional performance test such as SEBT can be used to asses balance disorders from vestibular or neurological origin is a myth. There is no ‘one size fits all’ when it comes down to physical performance.

For instance, subjects with chronic ankle instability may present with joint laxity and / or functional deficit in using their muscles and joints together to achieve functional dynamic control of their body. Research tells us that this group may show reaching deficits for the posteromedial direction whilst performing a Y-balance test. Also from the literature, certain differences between limbs in dynamic control can put one at higher risk of developing chronic ankle instability or have and ACL injury. Therefore, those tests can also be used to assess and identify people that would benefit from a program to prevent or minimise the risk of injuries. It is paramount to highlight that 6 weeks of neuromuscular training seems to be effective in reducing the risk of a second ankle sprain in those who present an acute lateral ankle sprain.

Closed Kinetic Chain Upper Extremity Stability Test

Lastly, an example from the upper body: the Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST), certainly a big name for a simple, reliable and functional test for the upper limb.  CKCUEST main goal is to assess one’s shoulder stability through movement whilst shifting weight from one hand to the other in a full push up position. It is expected that healthy or at low injury risk individuals would be able to shift their weight from side to side at a given pace within a specific time. So the assessor will look for any signs of fatigue which would show as poor form whilst executing the test, inability to sustain a certain pace, symptoms such as pain etc. Scapular or shoulder girdle stability is crucial for several sports, to name a few: tennis, cricket, volleyball, surfing, swimming etc. Interestingly, upper body strength also plays a part in running performance and should be considered accordingly in the context of running performance.

One of the most common non-traumatic injury mechanisms in the shoulder is related to poor scapula control and rotator cuff strength/flexibility is subacromial impingement syndrome. This is where the muscles around the shoulder blade and shoulder joint fail to support and stabilise the shoulder complex through range whilst the hand moves across the space, such as when someone is serving a ball in tennis. As a consequence of poor mechanics, the orientation of the shoulder joint as well as the positioning of the head of the humerus (arm bone) is affected leading to a dysfunctional movement pattern and causing the impingement of local tissue. Several muscles are involved in that movement and a thorough assessment is required in order to identify those at risk or presenting with dysfunctional movement.  Another great example comes from swimmers, which require good scapula control and shoulder internal rotation in order to develop a strong catch and efficient high elbow during early stages of the recovery phase.

In summary, the take home message here is: functional testing are simple, reliable and effective in the clinical setting in helping physios and clients alike to identify potential problems that are or could be interfering with one’s physical performance. It can be applied for a multitude for purposes, from elite performance individuals to those that just want to rehab their injuries, be pain-free and carrying on with their lives. Nevertheless, it is crucial to stress that those tests must be used within the proper context. To approach them with a ‘one size fits all’ mentality when applying, or interpreting results, is likely to lead to the wrong conclusions.

Bruno Rebello (APAM)

Physiotherapist

References

1. Brophy RH, Chiaia TA, Maschi R, Dodson CC, Oh LS, Lyman S, et al. The Core and Hip in Soccer Athletes Compared by Gender. International Journal of Sports Medicine Int J Sports Med. 2009Jul;30(09):663–7.
2. Cruz-Diaz D, Lomas-Vega R, Osuna-Pérez M, Contreras F, Martínez-Amat A. Effects of 6 Weeks of Balance Training on Chronic Ankle Instability in Athletes: A Randomized Controlled Trial. International Journal of Sports Medicine Int J Sports Med. 2015;36(09):754–60.
3. Hall E, Docherty C, Simon J, Kingma J, Klossner J. Strength-Training Protocols to Improve Deficits in Participants With Chronic Ankle Instability: A Randomized Controlled Trial. Journal of Athletic Training. 2015;50(1):36-44.
4. Tucci H, Martins J, Sposito G, Camarini P, de Oliveira A. Closed Kinetic Chain Upper Extremity Stability test (CKCUES test): a reliability study in persons with and without shoulder impingement syndrome. BMC Musculoskeletal Disorders. 2014;15(1):1.
5. Nakagawa T, Serrão F, Maciel C, Powers C. Hip and Knee Kinematics are Associated with Pain and Self-reported Functional Status in Males and Females with Patellofemoral Pain. International Journal of Sports Medicine. 2013;34(11):997-1002.
6. Paterno M, Schmitt L, Ford K, Rauh M, Myer G, Huang B et al. Biomechanical Measures During Landing and Postural Stability Predict Second Anterior Cruciate Ligament Injury After Anterior Cruciate Ligament Reconstruction and Return to Sport. The American Journal of Sports Medicine. 2010;38(10):1968-1978.
7. Powers C. The Influence of Abnormal Hip Mechanics on Knee Injury: A Biomechanical Perspective. J Orthop Sports Phys Ther. 2010;40(2):42-51.
8. Teng HPowers C. Sagittal Plane Trunk Posture Influences Patellofemoral Joint Stress During Running. J Orthop Sports Phys Ther. 2014;44(10):785-792.
9. Webster K., Gribble P. Functional Rehabilitation Interventions for Chronic Ankle Instability: A Systematic Review. J. Sports Rehab. 2010, 19, 98-114

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