C. MOVEMENTS VS. MUSCLES

As discussed above there is a plethora of variables, which effect FMD. There are numerous current literature sources emphasising that the capability required for efficient movement is done so through integration of numerous muscles working in combination over a number of joints, rather than isolated muscle strength (7, 13, 17, 21).

Cook (17) explained simply that when analysing movement our brain does not recognise individual muscle activity, instead the brain recognises movement patterns and creates coordination between all the muscles needed, a process that is referred to as a ‘motor program’. Boyle (7) also emphasised the philosophy of FMD by stating, “experts emphasise that functional training trains movements, not muscles”. Boyle (7) noted that research and development demonstrates that exercise prescription should not follow anatomical descriptions for movements based on patterns such as extension / flexion / adduction only to produce force, but rather follow patterns of kinetic chains, which is how the body moves in actual locomotion. This concept describes groups of muscles and joints working together to perform movements.

Epley (21) concurred with this philosophy and noted that for an exercise to improve athletic performance multiple joint actions must be timed in the proper neuromuscular recruitment patterns. The training of multiple joints in one exercise will aid in the development of coordination and improve the ability to generate force for sports movements. He also stated that single joint exercises such as bicep curls, leg curls, and leg extensions contribute little to improve performance and are only used broadly to enhance an aesthetic quality, where multi-joint actions are a much better option for providing a transfer from training to performance. He concluded by stating, “sports skills require multiple joint actions timed in the proper neuromuscular patterns, otherwise you have no coordination or ability to generate explosive force”.

Chek (13) discussed generalised motor program compatibility, when referring to the concept that the brain stores “generalised motor programs”. He discussed that each motor program can be used for groups of movements that have the same relative timing. He gave an example when discussing a squat movement pattern, where he noted research demonstrated that when performing isolation exercises such as a leg curl / leg extension, there is a very poor transferal effect to improving vertical jump (VJ) performance. However there was a significant improvement in VJ performance when training the resisted squat pattern. This VJ performance concept was furthered when Dalen et al. (19) provided evidence of single joint (SJ) vs. multi joint (MJ) training with VJ performance. Their study was performed analysing proximal to distal coordination between the knee and ankle upon VJ performance. The study looked at two separate groups, where group ‘A’ completed MJ ballistic squat training with plantar-flexion in one complete movement, and group ‘B’ completed SJ plantar-flexion and ballistic squat resistance movement training on separate days. The study found that only the group ‘A’ MJ training group had a significant increase in their maximal VJ performance.

Boyle (6) described SJ or isolation exercises as non-functional for injury prevention and sports performance.  He gave alternative exercise prescriptions such as instead of leg extensions the use of split squats or other single leg variations, instead of leg curls using a single-leg-straight-leg deadlift prescription. He noted that over recent decades training prescription has progressed from training by body part to a more intelligent approach to training via movement pattern.

Gentil et al. (27) studied the effect of additional SJ exercises to a MJ resistance program, where the goal was to enhance muscular hypertrophy and muscle strength. The study randomly divided untrained men into a group ‘A’ training MJ exercises only with bench press / lat. pull down, and group ‘B’ training MJ and SJ exercises together with bench press / lat. Pull down / elbow flexion / elbow extension. The study concluded no additional muscular size or strength benefit was seen with the inclusion of SJ exercises, when elbow flexion was measured with isokinetic strength testing, and hypertrophy was measured with ultrasound.

The approach taken by the strength and conditioning professional should follow the literature which now overwhelmingly demonstrates that exercise prescriptions for sports performance should follow a method of enhancing motor development via movement based exercise prescription models.  The enhanced complexity of sports performance can only be further improved by incorporating an integrated functional approach to training prescription.

G. KINETIC LINK PRINCIPLE

The kinetic link principle (KLP) refers to the method in which the body produces momentous force. A summation of forces is produced through the body via a  ‘linking’ process of a number of segments together (37). Diagram 5 produced by Kreighbaum et al. (37) describes a sequential process by which a force is produced. It describes force starting from the proximal segments of the body and progressively transferring momentum to the distal segments. This is possible via the proximal segments being larger in mass and having a greater inertia. An upper body throwing action may be used as an example. The initial segments (i.e. trunk rotators) accelerate eliciting a force, where the next body segment (i.e. shoulder horizontal adductors / internal rotators) then initiates an accelerating force, which then refers on to the upper arm (i.e. elbow extensors), and the end point (wrist and finger flexors). The key to this process is that each segment is smaller than the previous and contains less inertia. As one segment accelerates it allows the following segment to initiate movement at its top speed as it passes on momentum to the next segment before it decelerates.  The speed of the consecutive segments gradually increases, with the result allowing the end point velocity of the final segment to be much greater than the initial. This biomechanical process occurs through the “serape / functional line effect” as mentioned previously, and can be applicable to not only a throwing action, but a range of different functional skills.

Subijana et al. (57) performed a biomechanical study on kinetic energy transfer during the tennis serve. They analysed two tennis player’s service actions via a system referred to as 3D photogrammetry, where a proximal to distal segment kinetic energy transfer was discovered by a mean correlation analysis. The analysis found that for one of the players it could successfully predict the quality of the serve with 100% accuracy and the other player 76%, based on the kinetic transfer properties seen during the action.   

Roetert et al. (52) referred to a tennis serving action. He reported the following findings in the literature:

• The largest portions of kinetic energy or force generated in the serving stroke are developed in the legs and trunk, where 51% of the kinetic energy and 54-60% of the total force are produced.

• As seen in diagram 5 and 6, each segment has a cocking or stabilization phase, and an acceleration phase.

• Segment ‘drop out’ or kinetic chain breakage decreases the ultimate force and energy available to produce a forceful movement, and also puts excessive unnecessary strain on the surrounding segments. 

• A 10% reduction in energy transferal from the hip or trunk requires a 14% increase in shoulder rotation velocity or a 22% increase in shoulder mass to create the same amount of kinetic energy for the movement.

The KLP is a very trainable aspect of functional development where analysis of the process one uses to efficiently accelerate at different joints can be identified, and exercise prescription can be applied to enhance the method of force transferal through the body. This process is common in a number of sports such as baseball, golf and tennis (32, 57), where biomechanical feedback is given to the individual athlete so alterations can be made to decrease the potential for injury occurrence and improve the power profile through one or more specific sporting actions.

Diagram 5. The Kinetic Link Principle. Kreighbaum et al. (37)

Diagram 6. The Kinetic Link Principle In Action. www.timhartwig.com

(Transferal of momentum / summation of forces from proximal to distal)

H. IMPORTANCE OF POSTURAL SCREENING

Prior to initiating an exercise prescription a great deal of importance must be placed on an appropriate initial screening and assessment (36, 38). Over recent years, a larger degree of emphasis has been placed on this where ‘screening’ systems are now becoming a recognised part of the exercise prescription process for particularly athletic and also other populations (17, 18, 26, 30, 38, 58). An approach adopted by numerous authors demonstrates the use of initial postural screening, and subsequent movement screening to identify potential compensatory patterns an individual may use to complete a movement skill (29, 31). These compensatory patterns are then considered with the exercise prescription and rate of progression of individual prescription.

Postural analysis has been noted as an important factor to consider as an initial step to identifying potential movement asymmetry and discrepancy (36, 38). Kendall et al. (36) noted that in the standard posture the body is in the “ideal alignment for weight bearing”, where the body is in position that favors optimal function. Kritz (38) noted that a definition of optimal static standing posture is “when the least amount of physical activity is required to maintain body position in space and that which minimises gravity stresses on body tissues”. A postural screening identifies the degree of effort or most appropriate position the body uses to maintain a static standing (or seated) position. If an athlete has faulty static posture, this will relate to additional energy being required prior to producing a movement to get into the initial most appropriate position (38). Kritz (38) states that anticipatory strategies that contribute to faulty movement patterns are less efficient, causing the athlete to expend additional energy to perform a proficient movement, where anticipatory strategies have been seen to negatively influence power production. Kritz (38) noted that a range of authors stated that postural assessment indicates the presence of muscle impairments, which are also indirectly associated with movement impairments. Cook (17) when discussing posture noted that the way the body is held has a lot to do with the way that it moves, where the starting position influences the movement that is to follow. When the body begins in a sub-optimal position, receptor influence attempts to make up for the problem by unnecessarily altering the biomechanics in an attempt to catch up or correct the movement.

The observer must identify differences compared to the norm where variations in body type, shape, size, and proportion must also be considered for each individual. An example of optimal posture is demonstrated below, with an explanation of ideal position for larger joints of the body.

Table 3. Adaptation of Ideal Postural Criteria in a Lateral Position. Kritz (38)

Diagram 7. Ideal Posture in Lateral Position. Kendall et al. (36)

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).