When, as a sports support professional, you set about improving a patient or client’s core stability, what do you consider to be more important: perfect performance or specific recruitment patterns?
Your opinion on this question will probably vary depending on your own background, professional discipline, type of clients and rehab or training objectives. It will influence your approach to programme design, testing and evaluation of your patient’s core stability.
Rather than provide a single definitive ‘answer’ to the question, I want to take one practical exercise-based test as a way of thinking about this issue. The exercise test is the forward lunge. In the training repertoire, the lunge is a ‘meat and potatoes’ strength exercise for the quadriceps and gluteals, but it doubles up very well as a ‘functional’ test of movement quality and postural control, because the basic movement pattern is commonly executed in a range of everyday activities and has very broad applicability. Broken down, the exercise is complex and hard to perform perfectly, which makes it a good test and analytical tool.
The key underlying philosophical questions here are:
I will return to some of these questions, but first let’s look more closely at the exercise.
Gray Cook (1) uses the lunge as part of a ‘functional movement screen’: a series of eight movements with specific performance criteria. Together the movements are designed to test a range of athletic skills and human coordination.
Based on this concept, I describe the exercise in Table 1 below in terms of a test with movement and performance criteria. In the righthand column I have added in the relevant muscle function to facilitate the observer’s analysis and assessment. The fact that there are so many detailed performance criteria tells us how complex the movement is, particularly in requiring the coordination of many stabilising muscles and good balance between opposing muscle groups.
The patient should be dressed in shorts and T-shirt (tucked in) or bra top so that you can fully observe all relevant body parts. Ask the patient to perform three lunges on each lead leg, and observe each of the three from the three different positions.
A perfect performance will involve six faultless repetitions of the lunge. If the patient falls short on one of the movement or performance criteria, make a note, for instance by placing a cross or tick against each criterion as you observe it. Refer to the muscle function column to help you identify the specific strength, flexibility or balance problem. You will be able to repeat the test at a future point, to assess your client’s improvement.
||Restricted range of movement may show insufficient flexibility in hip flexor, quadriceps and calf group|
||Tense upper body and poor breathing control or breath-holding indicate that the large superficial muscles (eg, rectus abdominis, upper trapezius, pectoralis major) may be overactive in helping to stabilise the trunk|
|Performance criteria (side view)||
||Deviation suggests poor or unbalanced muscle recruitment of trunk extensors|
||Weak gluteals and/or poor coordination will lead to the use of back extension to assist hip extension on the upwards phase|
||Unstable pelvis shows poor muscular control and balance. Specifically, recruitment of deep abdominals and gluteus maximus may be weak or non-existent, and flexibility in hip flexor and lumbar extensors may be inadequate|
|Performance criteria (front view)||
||Wobbles and sideways leaning reveal poor balance|
||Deviations suggest muscular imbalance between lateral hip muscles, specifically weak recruitment of abductors and possibly poor flexibility in ITB and adductors|
|Performance criteria (rear view)||
||Inability to hold level pelvis indicates poor muscle recruitment of gluteals medius and minimus|
You will of course need to use your skills and knowledge of your client to make an accurate diagnosis of their weaknesses and target areas for improvement. For example, if the client cannot retain a neutral lumbar spine and goes into excessive lordosis during the lunge, this suggests poor muscle balance across the pelvis. If you already know that your client has good flexibility in hip flexors and erector spinae, you can deduce that it is the recruitment of the deep abdominals and/or gluteus maximus that is the culprit.
This test relies on observation and interpretation, which some will see as a drawback. There is bound to be subjective variation in the diagnosis, as different practitioners focus on different aspects of the movement. This is why it is important to analyse all the movement and performance criteria, to try and minimise the scope for error by taking into account all aspects of coordination, muscle recruitment, flexibility and muscle balance.
To return to the questions I posed earlier: how valid is the lunge test in measuring your patient’s core stability? In my opinion the test’s credibility rests on the assumption that if the patient can achieve perfect posture, alignment and an efficient coordination of the movement then the correct muscles will be working at the right time. This is not an uneducated assumption, but one that is difficult to back up with research.
Does that matter? One viewpoint says not: as long as perfect form occurs, it does not matter which muscles are recruited to do the job. Practitioners agreeing with this philosophy would find a test such as the lunge very useful, satisfying the objective of developing movement skills to achieve increased core stability.
One advocate is FM Alexander, who considers the lunge a fundamental movement skill that needs to be perfected in order to achieve perfect posture in daily life. Teaching this movement is a key part of Alexander Technique, because the lunge movement occurs all the time in everyday activity. A walking step can be seen as a mini lunge; balancing forward on your front foot to reach for something from a cupboard involves a lungetype movement.
The US core stability specialist Paul Chek also sees the lunge as a ‘primal’ movement pattern. Achieving perfect form and stability during the lunge movement will, he argues, transfer across to achieving good posture and core stability in daily life and athletic movements. Indeed, both Chek and Cook discuss the idea of a few fundamental movements that can be tested and worked on to gain better functional core stability. This philosophy of achieving perfect form of key movements supports the use of the lunge as a test of core stability.
The contrary view is based on the research that shows the small deep core stabilising muscles – transverse abdominis and multifidus – are recruited at low levels during all movements. The omnipresence of the TvA and MF recruitment is then interpreted as proving that these muscles must be trained in isolation to ensure good core control. This philosophy is implicit in, for instance, the Pilates approach to core stability, and has been extensively written about in SIB and elsewhere.
Every movement task that we perform involves a specific muscle recruitment pattern to achieve the task. While transversus and multifidus may be constantly active at some proportion of their maximum capacity, each movement will also require many other muscles to be engaged, depending on the movement and the loads involved.
While there certainly is variation between individuals’ muscle recruitment given the same movement, the extent of the variation is limited if you impose specific performance criteria, as described above with the lunge. Most important, I feel, will be the ability to perform a movement such as the lunge with good relaxation and natural breathing. If the performance is relaxed, then the attainment of perfect form can be considered to involve good recruitment of the correct muscles.