Cause, consequence and therapeutic exercise for lower-back issues.
Myths and controversies regarding spine function and injury mechanisms are widespread. Consider the “cause” of back troubles, specifically the common perception that injuries occur during an “event.” Generally, statistics are compiled from epidemiological approaches, which ignore the large role of cumulative trauma. Despite a reporting system that tends to associate injuries with specific events, very few back injuries actually occur this way.
Evidence of the process of disk herniation (bulging or extrusion) provides a proof of principle. For example, the damaging mechanism leading to herniation, or prolapse, is repeated lumbar flexion requiring very modest concomitant compressive loads (Callaghan & McGill 2001). This trauma accumulates with little indication to the future client. With repeated flexion cycles, the annulus (rings of collagen that form the disk’s periphery) breaches layer by layer with progressive delamination (separation of the collagen rings) of the layers (Tampier et al. 2007), which allows nucleus material to accumulate gradually between the delaminated layers. The location of the annulus breaches can be predicted by the direction of the bend. For example, a left posterior-lateral disk bulge will result if the spine is flexed with some additional right lateral bend (Aultman, Scannell & McGill 2005). Subsequent twisting can lead to circumferential rents in the annulus.
This is critical information for the trainer, in terms of both prevention and postrehab. Avoiding a specific directional cause such as this will lead to optimal therapeutic exercise design, including the elimination of activities that replicate the cause.
Effective spine stabilization approaches must begin with a solid understanding of stability. From a spine perspective, this has little to do with the ability to balance on a gym ball, which is simply the ability to maintain the body in balance. In many instances a spine that is unstable is also flexion intolerant, with an associated intolerance of compression. Sitting on an exercise ball performing movement exercises increases spine compression to a flexed spine.
True spine stability is achieved with a balanced stiffening (co-contraction) of the entire musculature, including the rectus abdominis and abdominal wall, the quadratus lumborum, the latissimus dorsi and the back extensors (longissimus, iliocostalis and multifidus). Instability results in unwanted motion that leads to pain and/or tissue damage. Focusing on a single muscle generally results in less stability. It is impossible to train or activate muscles such as the transversus abdominis or multifidus in isolation. Interestingly, abdominal hollowing techniques reduce the potential energy of the column, causing it to fail at lower applied loads (McGill 2009). There are some provocative tests (tests that use motions, postures and loads to provoke pain or discomfort)—among them the shear test—that will help reveal which classification of client is best suited for a stabilization approach (Hicks et al. 2005).
Many therapy and postrehab approaches have the objectives of strengthening muscle and increasing range of motion in the spine. This is problematic (Parks et al. 2003), since those who have more motion in their backs are at greater risk for future back troubles. The benefits of strength training depend on the amount of control and endurance used by the exerciser. Interestingly, the differences between those with chronic, recurring back issues and matched asymptomatic controls 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 should therefore be targets for therapeutic and postrehab exercise.
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 yet less endurance than matched asymptomatic controls (McGill et al. 2003). Those with back issues also 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 commonly be both a consequence and a cause of back troubles. This gluteal amnesia occurs in people who do not engage the gluteal muscles because of a history of pain during hip extension tasks. Obviously, for this category of client, exercises to enhance the integration of the gluteal muscles will help their backs (and knees). Optimal back exercise therapy results from identification of perturbed patterns, followed by specific corrective exercise.
The first step in any exercise progression is to remove the cause of the pain, namely the perturbed motion and motor patterns. For example, flexion-intolerant backs are very common. Stretches such as pulling the knees to the chest may give the perception of relief (via stimulation of the erector spinae muscle stretch receptors), but this approach only guarantees more pain and stiffness as the underlying tissues sustain more cumulative damage. Eliminating spinal flexion, particularly in the morning when the disks are swollen after bed rest, has proven very effective with this type of client. Realize that the spinal disks can bend only so often before damage ensues. Reserve the bends for essential tasks, such as tying shoes, rather than abdominal training.
Preventing the cause (i.e., a flawed movement pattern) is far more effective and less complicated than you might think. Consider the client who stands slouched, with back muscles contracted to the point of chronic muscle pain. Rather than relying on muscle relaxants, you can address the postural cause, design an appropriate exercise program and remove the associated crushing load from the spine.
Determining the tolerance and capacity of each individual is paramount in ensuring that a given exercise dosage is properly assigned. Each individual has a loading tolerance, and when that is exceeded, pain and ultimately tissue damage will result. For example, a client may tolerate a bird-dog 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 can perform before pain or troubles begin. Someone who can walk only about 65 feet (20 meters) before pain sets in has a low capacity. Performing therapeutic exercise three times per week won’t benefit this person; she has a better chance with three sessions per day. This is an alternate approach to building capacity. Typically, clients will progress to one session per day as their pain-free capacity grows.
Any assessment should incorporate a strong biomechanical foundation. At the first meeting, form impressions regarding sitting posture, how the client rises from a chair, initial gait pattern, etc. (see Figure 1). Then take a history, looking for injury mechanisms and perceived pain exacerbators and relievers. Observe basic motion patterns, and delve further into the mechanics and nature of the symptoms. Then perform provocative and functional tests to identify motion and motor patterns that are tolerated. Include ranges of motion, postures and loads. Use all this information to formulate a corrective exercise plan that specifies the starting dosage of tolerable therapeutic exercise.
Figure 1: Poor standing posture (A) leads to constant spine load and chronic contracture of the erector spinae muscles, causing muscular pain. With improved posture (B), pain can be relieved.
Provocative testing is a potent tool in the assessment of back problems, and is easily performed. A posture-modulated tolerance test (see Figure 2) provides powerful information and can serve as a guide to avoid damaging/exacerbating activity; it also helps in designing appropriate therapy.
Figure 2: Provocative testing can determine the client’s compressive load tolerance. The client compresses the spine by grabbing the side edges of the seat and pulling down. When this is done with an upright back (A), the torso is stiffened with muscle activity. The client then repeats the test with slouched posture (B). Discomfort in this position compared with the upright-back version shows a lower tolerance when the spine is flexed (a flexion-intolerant client). This reveals where the spine tolerance is highest, indicating a suitable starting posture for therapeutic exercise.
More practical information can be gleaned from simply asking whether a client has better or worse days. 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, avoiding 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, especially as you add specific exercises designed to combat the cumulative stresses of sitting.
First of all, you must remove the movement flaws that cause clients back pain throughout the day. The controversial recommendation to “bend the knees and keep the back straight when lifting” rarely addresses the real issue, despite being popular. Few clients are able to use this strategy in their jobs, and furthermore this is often not the best strategy. The “golfer’s lift” (a move used to extract a ball from the cup—one leg extended backward as a counterweight to forward flexion, with the motion occurring at the hips, not the spine) is much more joint conserving for repeated lifting of light loads from the floor. Also, a client who transitions to lying down using a deep squat is overloading the back. Squatting is appropriate for getting off a toilet or chair, but not for dropping to the floor. A lunge that does not bend the spinal disks is a much more appropriate choice and builds capacity.
A standard and popular approach to abdominal training is to perform sit-ups or curl-ups over a gym ball. But consider the rectus abdominis, where the contractile components are interrupted with transverse tendons, giving the “six-pack” look. The rectus abdominis muscle is not designed for optimal length change, but rather for functioning as a spring. Why have transverse tendons in the rectus abdominis? The reason is that when the abdominals contract, “hoop stresses” are formed by the oblique muscles. These stresses can split the rectus apart. In addition to the springlike architecture of the rectus abdominis muscle, consider how it is used. People rarely flex the rib cage to the pelvis (i.e., shorten the rectus) in sport or everyday activity. Rather, they stiffen the abdominal wall and load the hips or shoulders. If this is performed rapidly (e.g., during a throw or movement direction change), the rectus functions as an elastic storage and recovery device.
In weight lifting, the rectus stiffens to efficiently transmit the power generated at the hips through the torso. Those who do actively flex the torso (think of cricket bowlers and gymnasts) are the ones who suffer with high rates of disk damage and pain.
Now revisit the curls and sit-ups over the ball. Can you see that this is a rather poor choice of exercise for most situations, as it replicates the injury mechanics yet doesn’t create the athleticism that enhances performance? Keep the ball, but change the exercise 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 far superior exercise for most people (see Figure 3).
Figure 3: Curl-up over a gym ball stresses the disks and unwisely uses capacity, while the “stir the pot” exercise (shown above) avoids motion in the painful disks and builds abdominal athleticism.
There are six stages of therapeutic exercise for postrehabilitation:
1. Corrective Exercise: Identify Any Perturbed Motion and Motor Patterns. The first time any exercise is performed, it is considered a provocation test. If it is tolerated, you proceed. If it is not tolerated, the technique is re-examined and adjusted. For example, gluteal muscle activation retraining cannot be accomplished with traditional squat training. People with chronic back pain tend to use the hamstrings for hip extension, and subsequently the spine extensors for back extension, creating unnecessary crushing loads. Gluteal muscle reintegration helps to unload the back (see Figure 4). Another critical concept in this stage of exercise design is that technique matters. It is not enough simply to perform an exercise; for improvement it must be performed with perfection.
Figure 4: Chronic back pain tends to cause people to use the hamstring muscles instead of the gluteals to extend the hip. Performing the back bridge, squeezing the gluteal muscles and eliminating the hamstrings helps to establish gluteal dominance during hip extension. (Clinical cues are presented in McGill 2009).
2. Groove Appropriate and Perfect Motion and Motor Patterns. The next stage in the progressive algorithm is to groove patterns to ensure stability. An example of this would be the “shortstop slide,” in which the client slides the hands down the thighs, moving the pelvis posteriorly. This action should be repeated daily so that the client encodes it as a “spine- sparing” movement pattern.
3. Build Whole-Body and Joint Stability. Stability is considered at two levels: joint (in this case spine stability) and whole-body stability. Quantification of stability proves that these two objectives are fundamentally different and need two different exercise approaches. Variations of the “big three” stabilization exercises (curl-up, side bridge and bird-dog) have been quantified and selected for their ability to ensure sufficient spine stability and optimal motor patterns. They spare the spine many injury mechanisms and pain exacerbators and are designed to build muscle endurance (see Figures 5 and 6).
Figure 5: The “big three” stabilization exercises are curl-up (A), side bridge (B) and bird-dog (C). While many variations and progressions have been quantified, there are several cues for correct form. For example, during the curl-up, cue clients to try and remove any motion from the lumbar and cervical segments of the spine. Progressions can include prebracing the abdominal wall and elevating the elbows off the floor, among others. For the side bridge, have beginners do sets of 10-second contractions before attempting more challenging progressions. With the bird-dog, have clients make a fist and co- contract the arm and shoulder; this progression enhances the contraction levels in the upper erector spinae. >>
Figure 6: There are many progressions, from low joint-load stabilization exercises to beginners’ variations that stiffen and balance the anterior (A) and posterior (B) chain.
4. Increase Endurance. After building stability, the next step is to enhance specific muscle group endurance. Spine stability requires that the musculature be co-contracted for substantial durations but at relatively low levels of contraction. This is an endurance and motor control challenge, not a strength challenge. For clients wanting to accomplish daily living activities without pain, this is sufficient. Although strength may improve, it is not specifically trained, since this requires overload and elevated risk, which should be reserved for performance training.
Keep in mind that you need knowledge of spinal loading and associated muscle activation levels when planning optimal exercise progressions (see Axler & McGill 1997; Callaghan, Gunning & McGill 1998; Kavcic, Grenier & McGill 2004a; and Kavcic, Grenier & McGill 2004b for examples of evidence-based exercise progression decisions).
TRAINING FOR PERFORMANCE
Whether they have athletic objectives (such as wanting to play golf) or demanding occupations, many clients will fall into the category of training for performance. However, many confuse health objectives (minimizing pain, developing joint-sparing strategies) with performance objectives (which require risk) and compromise their progress by engaging too early in specific strength training. But for those who do wish to enhance performance or athletic ability, the final two stages are recommended.
5. Build Strength and
6. Develop Speed, Power and Agility. Training the back for performance (athletic or occupational) requires different approaches and objectives than training to fulfill postrehabilitation objectives. A note is needed here: power development in the spine is usually very risky. Instead, power is developed about the shoulders and hips, both to increase performance and to minimize risk to the spine and related tissues.
Consider speed training. Many train by using resistance exercise to gain strength. But speed usually requires superior relaxation. The golf swing exemplifies this apparent paradox. Initiation of the down swing involves some muscle contraction, yet too much contraction actually slows the swing. At the instant just before ball contact, good golfers undergo a full-body contraction, which creates a superstiffness throughout the entire linkage. Then, just as quickly, the stiffening contraction is released to allow compliance and speed in the swing follow-through. This same cyclic interplay between relaxation for speed and contraction for stiffness is measured in the best sprinters in the world, the best lifters and so on. Techniques of superstiffness are important to understand, especially if you have clients who may be able to grasp some of these concepts and, for the first time perhaps, rise from the toilet or chair unassisted.
Finally, consider exercises such as the squat. Interestingly, neither world-class strongmen (who carry heavy loads) nor professional football and soccer players who run, plant the foot and cut are trained with the squat, as it does not emphasize the quadratus lumborum or the abdominal obliques (which these athletes use). Have clients spend less time doing squats, and redirect them to asymmetric carries, such as the farmer’s walk or bottoms-up kettlebell carry (see Figure 7), which build the needed athleticism in a much more “spine-friendly” way. In great athletes, power is generated in the hips and transmitted through the stiffened core. They use the torso muscles as antimotion controllers, rarely as motion generators (throwers are an exception to this).
Increasing your knowledge of issues related to pain in the lumbar spine will help you become an elite corrective-exercise and training specialist. Invest the effort to enhance your knowledge and techniques, and you and your clients will have success.
Figure 7: The asymmetric carry—such as the bottoms-up kettlebell carry (A) or farmer’s walk (B)— challenges the lateral musculature (quadratus lumborum and oblique abdominal wall) in a way never possible with a squat.