Thursday, 2 July 2015

E. FUNCTIONAL MOVEMENT ASYMMETRIES & DISCREPANCIES

The identification of functional movement asymmetries and discrepancies has been noted by numerous authors to be of major importance in the correct exercise prescription for athlete movement development (6, 10, 17, 24, 25, 26, 34, 35, 38). To establish a minimum benchmark of movement competence across a number of base movement skill qualities has been noted to be of high significance amongst initial training prescription for athletes (6, 7, 17). Where there is an asymmetry or discrepancy in the development of force, the athlete is contributing to a decrease in the amount of correct utilisation of momentum and energy, an increased potential of injury through improper biomechanics, and a potentially early onset of fatigue through physiological structures (6, 7, 17, 59).

Movement asymmetries and discrepancies can be classified as a process of poor biomechanics (17). This refers to movement ‘mistakes’ in which the body compensates and uses a process of sub-optimal joint alignment, postures, and coordinative applications (17). Tompsett et al. (58) discussed the common previous trend in assessment noting that coaches often focused on performance indicators such as speed and distance, where current trends are leading more towards the pre-season analysis of movements, identifying which athletes possess or lack the movement capability to perform essential movements required for sports performance. Progression of sports specific skills may be restricted by the poor initial development of basic movement competencies, where individuals will progress to a point and then plateau in performance where they are then limited by their own movement inabilities.

Burton et al. (10) discussed the use of functional movement testing, which is to identify abnormal movement patterns, where when identified exercise interventions can be applied to normalise the dysfunctional pattern. Cook et al. (18) discussed the importance of injury prevention through the use of a screening tool. Cook et al. (18) noted an important factor in prevention is to quickly identify deficits in mobility, stability and symmetry because of their potential influences on creating altered motor programs throughout the kinetic chain. Keisel et al. (34) studied injury prediction following asymmetries into fundamental movement patterns. They tested American professional football players using the “Functional Movement Screen” (FMS) prior to starting the training camp. They stated that players who demonstrated a combination of asymmetry in 1 or more out of 7 tests and who had a score below the established safe “cut-off” were at a much higher risk for musculoskeletal injury. Zahalka et al. (61) studied strength asymmetry of soccer goalkeepers. Zahalka et al. (61) used three different VJ testing methods. They used the counter movement jump / counter movement jump with no arms / squat jump. Their results demonstrated that countermovement jumps produced the best VJ score, however also elicited the largest unilateral force asymmetry between legs. They stated that monitoring of power level and strength asymmetries in the preparatory phase of training enables identification of possible strength imbalances in elite soccer goalkeepers. Zahalka et al. (61) concluded that their screening was a useful tool for both future performance enhancement and injury prevention.

Cook et al. (18) explained the term “regional interdependence”, which is used to describe the relationship between regions of the body and how dysfunction in one region may contribute to dysfunction in another. Boyle (6) furthered this concept when he discussed the “joint–by–joint” approach when discussing the potential ramifications of asymmetry and discrepancy for the athlete. This theory involved conceiving the body as a stack of joints, where each joint has a specific function and is prone to predictable levels of dysfunction. A key feature to be noted is that the main purpose of each consecutive joint alternates between mobility and stability (see table / diagram 2). The concept states that injuries relate very closely to proper joint function, where a problem (discrepancy) at one joint usually presents as pain or altered function through compensation at the joint above or below. The theory suggests that if a mobile joint becomes immobile, the stable joint above or below is forced to move with compensation, becoming less stable and potentially painful. An initial example was provided in the case of the lumbar spine, where if there is loss of function of the joint below (i.e. poor hip mobility), the lumbar spine has to take over and provide increased mobility as compensatory function causing undue stress to the associated structures. The key process of this concept is to consider the state of function in the above and below joints to an area reported as having pain or discomfort. The exercise prescription is focused around incorporating increased mobility or stability of the nearby joint, which in turn restores appropriate function to the associated joint. The result effect being that each joint functions based only on its primary purpose. Boyle (6) uses a secondary example explaining the prolific nature of knee pain associated with ankle mobility issues. Many sports involve standing and running where an immobile ankle causes the stress of landing to be transferred to the joint above. The knee has to take on an increased role of mobility, where over time this causes increased stress to the structures of the knee.

Table 2. Adaptation of Joint-by-Joint Approach. Boyle (6)
Diagram 1. Anatomical Man. www.medindia.net

The literature demonstrates that appropriate FMD is associated with the identification process of asymmetry and discrepancy. Correct identification and subsequent individual exercise prescription is of importance early in the learning period for effective movement development (10, 18, 34, 58).  

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