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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