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Many authors now cite muscle imbalance and lax or hypermobile movement as sig- nificant factors in predicting injury risk (25-27). There is mounting evidence that poor flexibility is not a significant injury risk predictor as was once universally accepted (28,29). This then suggests that the uncontrolled movement (not the restriction) is the critical component of muscle imbalance to identify in screening and the priority for retraining in risk man- agement strategies.

Figure 2: Flexion dissociation test

used as retraining exercises to improve recruitment thresholds and increase reflex mediated stiffness of the back stability muscles. The back extensor muscles are trained to become more efficient at stabilising the spine against flexion stress and strain.

The process of dissociating movement at one joint from movement at another joint has potential benefits for retraining the stability muscles to enhance their recruit- ment efficiency to control direction specific stress and strain. The stability muscles can be trained to recruit in co- activation patterns to prevent movement in a specific direction at a vulnerable (or unstable) joint while an adjacent joint is loaded in that direction (24). This dissociation testing and retraining can be performed under low threshold (slow, non-fatiguing low load) or under high threshold (fast or fatiguing high load) conditions. In this way the stability system can be trained to control a specific uncontrolled movement ‘weak link’ (site and direction) while correcting either motor control (low threshold) or strength (high threshold) deficits. If there is good motor control and strength of excessive (hypermobile) range then this could be considered to be hypermobility with good functional stability.

LOW LOAD TESTING CATEGORIES 1 Standing small knee bend control 3 Standing arm control

5 Hands and knees limb control 7 Modified push-up 9 Lunge loading

Table 2: The five low and high load testing categories www.sportex.net

The ‘Performance Matrix’ With increasing evidence supporting the need to identify uncontrolled motion as part of screening processes, an innovative new screening tool has been developed. It has been designed to identify altered con- trol strategies in terms of the site and direction of uncontrolled movement. It has also been designed to assess the threshold of deficit. This tool, the Performance Matrix, has also been designed to assess multiple muscle inter- actions acting on multiple joints in func- tionally orientated tasks (30).

The ‘Performance Matrix’ is a 3 dimen- sional assessment system to iden- tify performance-related weak links in the movement sys- tem. It is represented by a cube made up of smaller blocks (Figure 3).

D I

The Performance Matrix tests for:

1. The site of the weak link - where the performance deficit is: ■ upper neck (UN) ■ lower neck (LN) ■ upper back (UB) ■ shoulder blade (SB) ■ shoulder joint (SJ) ■ low back/pelvis (LB/P) ■ hip (H) ■ lower leg (LL)

HIGH LOAD TESTING CATEGORIES 2 Sitting spinal dissociation 4 Crook lying limb control 6 Crook lying - limb loading 8 Standing shoulder loading 10 Explosive propulsion

R E C T I

O N

2. The direction of uncontrolled movement at the weak link: - which direction (3 cardinal planes) of loading is poorly dissociated (that is, the direction that is difficult to prevent or resist movement into: ■ Axial plane ■ rotation, winging

■ Sagittal plane ■ flexion, extension, posterior tilt, anterior tilt, hitched, forward tilt, for- ward glide

■ Coronal plane: ■ sidebend, lateral tilt, abduction, adduction, dropped, retraction

3. The threshold of loading failure: - whether the weak link is related to a motor control deficit or to a strength deficit: ■ low threshold motor control failure (low load and slow)

■ high threshold weakness (high load or fast)

The Performance Matrix uses 10 testing categories to identify any weak link in the

Low High

Flexion Extension Rotation Sidebend Abduction Adduction

UN LN SB SJ LB/P H LL Figure 3: The Performance Matrix

chain within multi-joint function. It iden- tifies the ‘weak link’ in terms of site, direction and threshold of uncontrolled movement. There are 5 low threshold motor control testing categories and 5 high threshold strength testing cate- gories. The testing categories are based on multi-joint functional tasks (Table 2).

Each testing category has several sub- tests that are functionally related to each other. An example of a low threshold test

23 THRESHOLD