Sarah Mottram outlines an assessment approach to help identify a client’s weak links
In recent years the importance of stability training has been recognised but it remains more art than science: to date there is a lack of specificity in stability assessment and retraining. Over the last 10 years much evidence has emerged to demonstrate the link between movement faults and musculoskeletal pain. Faulty movement patterns develop over time through the normal stresses of life, training or sporting activities. Chronic states and recurrences of musculoskeletal pain have been linked with changes in strategies for motor control. In particular, individuals in such states of pain, according to the literature, change their motor control strategies for their ‘low-load function.
Low-load functional activities include:
maintenance and adjustments of postural positions
normal functional movements of the unloaded limbs or trunk.
People with faulty movement control tend to use high-load strategies for low-load contro. The particular movement faults can only be identified on low-load testing. Further research studies have shown that correcting these faults leads to a decrease in pain, increases in ranges of motion and improvement in function.
Equally important in the sporting environment is the assessment of high-load stability, which has been more widely described. It is essential that athletes undergo assessment of their high-load stability control. Therapists and coaches therefore should ensure their athletes undergo detailed assessment designed to identify movement faults and to find areas of uncontrolled movement (stability faults) under low and high load.
It is only possible to identify deficits related to inefficiency of low-threshold recruitment by using specific low-load tests, based on the accepted and extensive research on muscles such as transversus abdominis. Some lowload dysfunctions develop prior to the onset of symptoms and injury and appear to be precursors or contributing factors to the development of injury and symptoms(9,10). Muscle strength is measured as the ability to pass a test of resisting or supporting a high load. For the athlete, the objective of being strong is to maintain or improve performance.
But strength training does not resolve problems of pain and pathology or poor low-threshold motor control function.
From these principles it is possible to devise a protocol for assessment testing, to pinpoint stability dysfunction.
The stability dysfunction or ‘weak link’ is defined by the presence of inefficient or uncontrolled movement.
Based on the evidence to date:
*high-threshold retraining (strengthening) does not appear to correct motor control dysfunction in local stability systems *specific low-threshold training does appear to correct local and global motor control stability dysfunction(11,6)
*Low-load training does not appear to correct high-threshold dysfunction or atrophy.
Different mechanisms are used to control movement under low-load and high-load situations. When low and high load exercises are integrated together into a training programme, it is usually assumed that there is a linear progression from low to high load. However, there is no real evidence to support the concept of motor control training being a prerequisite for strength training. Specific testing can determine the appropriate retraining strategy to manage symptoms and improve performance.
Many strength training programmes are predominately designed to train strength at one joint and muscle at a time. Although sportspeople using such approaches pass strength tests in sporting situations, they often get injured under load. Their training fails to appreciate the difference between single-joint strength and multi-joint movement control (ie using two or more strong muscles together in a coordinated way under load). And two strong muscles working badly puts more intrinsic strain on the body than one weak muscle working badly.
In effect, athletes need two distinct types of training: strength work that targets the muscles of range and force potential; and motor control training for the deeper (force inefficient) muscles.
Towards an assessment system
The Performance Matrix is an assessment system developed from the latest academic and clinical research to determine the ‘weak links’ in the stability and performance chain. These weak links are identified in terms of: i. the site ii. the direction of musculoskeletal risk iii. the threshold (low or high) of potential performance failure.
The Performance Matrix can be used as a rehab tool, but will also help coaches and trainers to identify movement faults before symptoms become apparent.
The system has 10 tests (5 low load, 5 high load). To test for uncontrolled movement, the subject is asked actively to control the ‘weak link’ and move independently at the adjacent joint in the direction of testing. The ability to control the weak link can be assessed under both low-threshold (low load and slow) and high-threshold (high load OR fast) conditions.
The ability to prevent movement at the site of the weak link is rated as a ‘pass’ (able to demonstrate good active control) or ‘fail’ (unable to prevent uncontrolled movement). Where the athlete is able actively to control ranges of movement or to make compensations under both low- and high-load directionspecific testing, that aspect is not classified as a significant stability dysfunction. However, if movement cannot be controlled, the pattern is defined as a ‘weak link’.
This assessment tool makes it much easier for the support professional to design and implement a prescriptive retraining programme, including strategies to regain control of the site and direction of performance failure at the appropriate threshold of loading.
Case study illustration
In the following example, assessment results are shown for two tests on a footballer. He complained of a recurrent right hamstring ‘strain’, which had been affecting his performance. He’d had three severe episodes with a break in training and play. He had also complained of vague backache, which he had tended to ignore.
Previous management included some core stability training. The treatment regime had always cleared the symptoms in his hamstring and improved his strength but never prevented a gradual recurrence of symptoms two to three months after resuming training.
Performance Matrix testing identified some weak links. Two tests are described here in detail, along with the results achieved by the footballer.
Test A: Leg rotation under a neutral pelvis (low load)Start position
*Stand with the heels 5-7cm away from a wall and the back resting on the wall Stand feet under hips (10-15cm apart)
*Inside edges of the feet parallel
*Keeping heels down, bend the knees and slide down the wall
*Keep the kneecap out over the second toe
*The back should be straight and vertical as if sliding down a wall
*Position the shoulders midway between hitched up and dropped down.
Test movement: Swing the knees fully to the left and right without any movement of the pelvis and upper trunk
*As the knees swing side to side allow the feet to roll from inside to outside edge
*Move the feet one step away from the wall so the back is off the wall
*Repeat the movement without the wall support.
*The tester notes how far the knees move side to side.
Notes on protocol
First practise the test movement with the pelvis and trunk supported against a wall. If the client can’t reach the same range off the wall (unsupported) as they could on the wall, try turning one leg at a time. If the range moving one leg at a time is now the same, there is no restriction. If the range is still less, then there is a restriction of the foot or the knee that needs mobilising. The hip is unlikely to be the cause of restriction.
Test B: Elbow push-up plus single-leg lift (high load) Start position Lie face down propped on elbows with forearms and hands pointing to opposite elbow
*Knees and feet together
*Shoulders midway between hitched and dropped
*Taking weight through the arms, lift hips and knees off floor, pushing off the toes
*Make a straight line with legs, trunk and head.
*Test movement Keeping the pelvis neutral and in a straight line with the legs and trunk, lift one leg to horizontal.
The results demonstrate that this footballer has a low-load motor control rotation dysfunction of the low back and a high-load strength dysfunction controlling extension. This weak link into extension is often associated with recurrent hamstring problems.
This is linked with inefficiencies in the stability muscles (obliques and gluteals) from controlling lumbar extension and rotation (under both low and high load). The gluteals also contribute to active hip extension and, if inefficient, the hamstrings dominate the pattern of movement.
Although the footballer’s symptoms had always been cleared with previous treatments and rehab, the weak link was contributing to gluteal inefficiency and concurrent dominance of the hamstring (the synergist for the inefficient gluteals), which contributed to overstrain and recurrence of symptoms. From this assessment a specific retraining strategy can be implemented to correct the faults.
In this case, the footballer retrained control of lumbar rotation with a low-load strategy. This included retraining hip rotation (as described in the test) but with wall support and kinaesthetic feedback from his hands in his iliac crests. This was progressed away from the wall, to walk and then lunge. He performed repetitions of the movement, stopping when he could no longer control it. When he passed the test he could perform the movement for four minutes, demonstrating good low threshold lumbopelvic control.
The lumbar extension weak link was retrained with high-load strategies. The test position was modified to start with more thorax support (hip extension with the thoracic spine on gym ball). The importance of retraining this high-load weak link is to train under high load and not modify to low load (if he’d had a concurrent weak link under low load it may have been necessary to start retraining under low load). High-load retraining strategies must include load, speed or an unstable surface. Again he only performed the exercise if he could control the weak link. His goal was to work up to sustaining extension for two minutes, working always to the point of fatigue to ensure high-load training.
He passed both tests at six weeks and again six months after return to full training, and has not had a recurrence of symptoms in the hamstring or lumbar spine.