Designing Back Exercise: from Rehabilitation to Enhancing Performance (2012)

Designing Back Exercise: from Rehabilitation to Enhancing Performance
Stuart McGill, Ph.D. Professor of Spine Biomechanics,
Faculty of Applied Health Sciences, Department of Kinesiology, University of Waterloo
(Download PDF, 260Kb)

Many have asked me to write a short overview to assist increasing the competency of clinicians. But after writing two textbooks based on our hundreds of scientific publications, I feel as though I have already said what is necessary and important in a cohesive story. Here are few thoughts for exercise professionals who deal with issues related to the assessment and design of therapeutic exercise for the back, to assist them in becoming elite professionals. Many clinicians follow a “recipe” for assessment, treatment or performance training. Using this generic approach ensures “average” results – some patients/clients will improve and get better, but many will fail simply because the approach was above or below the optimum level necessary to address the deficit. The program and approach introduced here will help you to become an elite corrective exercise and training specialist. Invest the effort to enhance your knowledge and techniques and you will have success where others have failed. Many times, we have had a breakthrough with an influential client – be they a pro athlete or business person. Subsequently they become your best referral service.

The cause (and elimination of it) 

The first step in any exercise progression is to remove the cause of the pain, namely the perturbed motion and motor patterns. For example, the flexion intolerant back is very common in todays society. Giving this type of client stretches such as pulling the knees to the chest may give the perception of relief (via the stimulation of erector spinae muscle stretch receptors) but this approach only guarantees more pain and stiffness the following day as the underlying tissues sustain more cumulative damage. Eliminating spine flexion, particularly in the morning when the discs are swollen from the osmotic superhydration of the disc that occurs with bedrest, has been proven very effective with this type of patient. Realize that the spine discs only have so many numbers of bends before they damage. Keep the bends for essential tasks such as tying shoes rather than using them up in abdominal training. Many lifestyle and occupational examples are provided in the textbook “Low back disorders: Evidence based prevention and rehabilitation” to guide the elimination of the cause of a clients back troubles – the clinician will find that half of Resources: McGill, S.M. (2007) Low back disorders: Evidence based prevention and rehabilitation, Second Edition, Human Kinetics Publishers, Champaign, IL, U.S.A. McGill, S.M. (2007) (DVD) The Ultimate Back: Assessment and therapeutic execise, McGill, S.M. (2009) Ultimate back fitness and performance – Fourth Edition, Backfitpro Inc. Waterloo, Canada ( 2 their initial effectiveness will be due to preventing the cause (ie, a flawed movement pattern)! This need not be so complicated. Consider the client who stands slouched where the back muscles are chronically contracted to the point of chronic muscle pain. The family doc typically prescribes muscle relaxants which fail to work. The clinician addresses the postural cause and corrects standing to shut the muscles off and remove the associated crushing load from the spine. The client exclaims, “You’re magical – you just took the ache out of my back”.

Building the scientific foundation: 

Myths and controversies regarding spine function and injury mechanisms are common. Consider “the cause” of back troubles, specifically the common perception regarding common injury pathways in which the back is hurt in an “event”. Generally statistics are compiled from epidemiological approaches which ignore the large role of cumulative trauma. Compensation board data is often used however, and they ask clinicians to fill out reports and name the “event” that caused the “injury”. For example, “Mr X lifted and twisted” at the time that the injury occurred. Kinesiologists and clinicians know that twisting is different from generating twisting torque, but very few of the individuals filling out the reports will know. So, was it twisting torque? Or, was it being twisted, that caused the injury? Further, despite the injury reporting system geared to the reporting of the “event” associated with the “injury”, very few back injuries occur this way. Evidence of the process of disc herniation provides a proof of principle. For example the damaging mechanism leading to herniation, or prolapse, is repeated lumbar flexion requiring only very modest concomitant compressive loads (Callaghan and McGill, 2001). This trauma accumulates with little indication to the future patient. With repeated flexion cycles the annulus breaches layer by layer with progressive delamination of the layers (Tampier et al 2007). This allows gradual accumulation of nucleus material between the delaminated layers. The location of the annulus breaches can be predicted by the direction of the bend. Specifically, a left posterior-lateral disc bulge will result if the spine is flexed with some additional right lateral bend (Aultman et al, 2004). Subsequent twisting leads circumferential rents in the annulus that tends to make McKenzie extension approaches for these clients useless, or even exacerbating (Marshall and McGill, 2010). This is critical information for the clinician, both in terms of prevention and in treatment. Avoiding this specific directional cause will lead to optimal therapeutic exercise design together with elimination of activities in the patient’s daily routine identified as replicating the cause.

Many therapy approaches have the objectives of strengthening muscle and increasing spine range of motion. This is problematic (Parks et al, 2003) since those who have more motion in their backs have a greater risk of having future back troubles. Strength may, or may not, help a particular individual as strength without control and endurance to repeatedly execute perfect form increases risk. Interestingly, the differences between many “troubled backs” (the chronic back with recurrent episodes) and matched asymptomatic controls performing the same jobs have been shown to be variables other than strength or mobility. Rather deficits in motion and motor patterns have been documented as being more critical and thus should be targets for therapeutic exercise. For example, people with troubled backs use their backs more. Generally, they walk, sit, stand and lift using mechanics that increase back loads. Many of them have stronger backs but are less endurable than matched asymptomatic controls (McGill et al, 2003). They tend to have more motion in their backs and less motion and load in their hips. A common aberrant motor pattern is known as “gluteal amnesia” (McGill, 2007) which may be both a 3 common consequence of back troubles and probably a cause of them as well. Obviously for this category of client, exercises to enhance the integration of the gluteal muscles will help their backs, and also their knees. Optimal back exercise therapy results from the identification of these patients with perturbed patterns followed by specific corrective exercise – this precedes all other exercise therapy.

The science of spine stability: Effective spine stabilization approaches must begin with a solid understanding of what stability is. From a spine perspective it has little to do with the ability to balance on a gym ball. This is simply the ability to maintain the body in balance which is important but does not address the unstable spine. In fact, in many instances the unstable spine is also flexion intolerant and with associated intolerance to compression. Sitting on an exercise ball performing movement exercises increases spine compression to a flexed spine. This retards progress – it is generally a poor choice of back pain exercise until quite late in a therapeutic progression. True spine stability is achieved with a “balanced” stiffening from the entire musculature including the rectus abdominis and the abdominal wall, quadratus lumborum, latissimus dorsi and the back extensors of longissimus, ilioicostalis and multifidus. Focusing on a single muscle generally does not enhance stability but creates patterns that when quantified result in less stability. It is impossible to train muscles such as transverse abdominis or multifidus in isolation – people cannot activate just these muscles. Do not perform abdominal hollowing techniques as it reduces the potential energy of the column causing it to fail at lower applied loads (McGill, 2009). Interestingly a recent clinical trial (Koumantakis et al, 2005) compared the efficacy of many of the exercises that I quantified and published in Physical Therapy (McGill 1998), with the same exercises combined with specific transverse abdominis isolation (hollowing etc.). Adding the specific transverse abdominis training reduced efficacy! Instead, the abdominal brace (contracting all abdominal muscles) enhances stability. Target contraction levels for bracing and training techniques are described in McGill (2006). Finally, some provocative tests, such as a shear test, will help reveal which classification of patient is best suited for a stabilization approach (Hicks et al, 2005).

Tolerance and Capacity: Determining the tolerance and capacity of each individual is paramount to ensure that a given exercise dosage is matched to the client. Each individual has a loading tolerance which, when exceeded, will cause pain and ultimately tissue damage. For example, a patient may tolerate a birddog extension posture but not a superman extension over a gym ball which imposes twice the compressive load on the lumbar spine. A person’s capacity is the cumulative work that he or she can perform before pain or troubles begin. An example, someone who can only walk 20 meters before pain sets in has a low capacity. This kind of person won’t benefit from therapeutic exercise that’s performed 3 times per week; instead, he or she has a better chance with 3 sessions per day. Corrected walking in 3 short sessions per day, never exceeding the current tolerance and capacity, is an alternate approach to building capacity. Typically, patients will progress to 1 session per day as their pain-free capacity grows and then be tolerant of a good session with their clinicians.

Interpreting client presentation: Our approach to client assessment incorporates a strong biomechanical foundation, and blends expertise from various disciplines. First, an impression is formed from the first meeting of the client – their sitting posture, how they rise from the chair, their initial gait pattern etc (see figure 1). Then a history is taken looking for possible candidate injury mechanisms, and perceived pain exacerbators and relievers. Observation continues during some basic motion patterns as the evaluation process proceeds delving further into the mechanics and nature of the symptoms. Then provocative tests are performed to identify motion and motor patterns that are tolerated. Specifically we include a range of motions, postures, and loads. All information is used to formulate the plan for corrective exercise and the starting dosage of tolerable therapeutic exercise. The process concludes with functional screens and tests that were chosen based on information obtained in the preceding process (the assessment process is well documented in McGill, 2007). These results are used to substantiate some speculation as to the existence of perturbed motion and motor patterns and for considering exercise choice and rates of subsequent exercise progression.

Figure 1: Poor standing posture causes constant spine load and chronic contracture of the erector spinae muscles causing muscular pain (A). Rising from a chair with dominant hamstrings because of pain inhibiting the gluteal muscles causes higher back loads (B).

Example of some provocative tests that are helpful

Provocative testing is a potent tool in the assessment of back problems, and is easily performed. I have tried to illustrate a wide variety of these, together with some corrective techniques in a DVD (see McGill, 2007). See Figure 2 for an example of provocative testing for compressive load tolerance. This posture-modulated tolerance test provides powerful information and can serve as a guide to avoid damaging/exacerbating activity, and it also helps to design appropriate therapy.

Figure 2: An example of provocative testing. The patient compresses the spine by grabbing the side edges of the seat and pulling down. When doing this with an upright back (a), the torso is stiffened with muscle activity. The test is then repeated in a slouched posture (b); discomfort in this position as compared to an upright back shows a lower tolerance when the spine is flexed (and a flexion intolerant patient). This reveals where the spine tolerance is highest, and therefore a posture to begin therapeutic exercise.

More practical information can be gleaned from simply asking whether a client has better and worse days. Even though it seems straightforward, it can’t be stressed enough that if there are indeed better and worse days, it means that some activities help and others hurt. Find out what they are and eliminate the exacerbating elements. For example, if sitting isn’t tolerated, avoidance of flexion by using a lumbar support will help, together with organizing tasks to eliminate prolonged sitting. This is known as “spine hygiene” and will build more capacity for the client to work with you. Your efforts here will be well rewarded with more success. Specific exercises designed to combat the cumulative stresses of sitting are then prescribed.

Reducing the risk of injury:

No exercise professional can be fully successful without removing the movement flaws that cause of back troubles in patients throughout the day. Controversial recommendations such as “when lifting, bend the knees and keep the back straight” rarely address the real issue, despite their popularity. Few patients are able to use this strategy in their jobs and furthermore, this is often not the best strategy. For example, the “golfers lift” is much more joint conserving for repeated lifting of light loads from the floor. Another example illustrates the poor choice of movement strategies for a particular task. For example observe the client who transitions to laying on the floor by using a deep squat – this overloads their back. Squatting is appropriate for getting off a toilet or chair but not for dropping to the floor. Instead a lunge that does not bend the spinal discs is a much more appropriate choice. Again, this builds capacity for them to accomplish more in their training session with you (see McGill, 2007 for full explanation and evidence for spine sparing guidelines).

Linking Anatomy with Function:

Consider the usual and popular approach to train the abdominal wall muscles by performing situps or curl-ups over a gym ball for example. But consider the rectus abdominis where the contractile components are interrupted with transverse tendons giving the “six pack” look. The muscle is not designed for optimal length change but rather to function as a spring. Why have these transverse tendons in rectus abdominis? The reason is that when the abdominals contract, “hoop stresses” are formed by the oblique muscles that would split the rectus apart. In addition to Figure 2: An example of provocative testing. The patient compresses the spine by grabbing the side edges of the seat and pulling down. When doing this with an upright back (a), the torso is stiffened with muscle activity. The test is then repeated in a slouched posture (b); discomfort in this position as compared to an upright back shows a lower tolerance when the spine is flexed (and a flexion intolerant patient). This reveals where the spine tolerance is highest, and therefore a posture to begin therapeutic exercise. 6 the spring-like architecture of the muscle consider how it is used. People rarely flex the rib cage to the pelvis shortening the rectus in sport or everyday activity. Rather they stiffen the wall and load the hips or shoulders – if this is performed rapidly such as in a throw or movement direction change, the rectus functions as an elastic storage and recovery device. When lifting weights it stiffens to efficiently transmit the power generated at the hips through the torso. Those individuals who do actively flex the torso (think of cricket bowlers and gymnasts) are the ones who suffer with high rates of disc damage and pain. Now revisit the common training approach of curling the torso over a gym ball that replicates the injury mechanics while not creating the athleticism that enhances performance. This is a rather poor choice of exercise for most situations. Yet many clients will expect that a gymball be used. Play a trick on these clients and retain the gymball but change the exercise from a spine breaking curlup to a plank where the elbows are placed on the ball. Now “stir the pot” to enhance the spring and spare the spine – this is a much superior exercise for most people. (See figure 3).

Figure 3: Curlup over a gymball motions stresses the discs and unwisely uses capacity (a) while the `Stir the pot` exercise spares the painful discs of motion and builds abdominal athleticism (b).



To read the rest of this article please download PDF