Low back pain (LBP) is a widespread phenomena that is estimated to effect roughly 85% of individuals at some point in their life (1). In fact, globally LBP is the leading cause of disability (2). Considering the prevalence of LBP it’s important to gain a better understanding of the complex mechanisms and potential avenues for successful treatment and prevention. This article is neither diagnostic or a recommendation for treatment protocol. It’s simply here to inform you on the various intricacies of the subject so when you seek out professional help from a qualified physical therapist (which is the course of action I recommend) you are better equipped to be an active participant in your own treatment.
Chronic low back pain (CLBP) is defined as pain persisting for twelve weeks or longer (3). CLBP accounts for roughly 20% of LBP instances, but in up to 90% of these cases clinicians are unable to identify the cause, so CLBP is labeled as non-specific CLBP (4). A review conducted by Bart W. Koes and colleagues on the clinical guidelines for the management of non-specific low back pain in primary care found the primary treatment modalities were education, medication, exercise, manipulation, bed rest, and referral to a specialist (5).
Treatment protocols were categorized based on country, and as the results demonstrate, prescriptions were rather varied (See Reference Table Here). LBP appears to be more prevalent in woman than men, with a heightened sensitivity to pain documented in women due to biological, psychological and environmental factors (6)(7). CLBP is also influenced by genetics and age, with increased risk of LBP being associated with advanced age (8).
Mechanisms Of Low Back Injury:
The mechanisms of low back injury/pain are complex, as such we need to establish distinctions between injury and pain along with operational definitions for both. Injury is biological, such as disc herniations, fractures, muscle tears etc. Pain is a complex interaction of biophysical, psychocognitive, and sociocultural processes (9). However pain and injury are not mutually inclusive, but we will explore this in greater detail later.
Injury can be defined as a tissue being taken beyond its functional loading capacity (10). It’s estimated that 95% of all disc herniations occur in the lumbar spine with the significant preponderance occurring posterior or posterolateral as depicted in the image below (11).
However, the placement of the anterior longitudinal ligament mitigates anterior displacement making anterior herniations quite rare.
Rapid increases in compressive force (such as jumping or axial loading), high or low load flexion/extension motions, and flexion-rotation are all associated with disc herniations (12). However the relationship between LBP and disc herniation is scant. Estimated to be just 2-5% (13). Researchers have demonstrated sheering and compressive forces act on the discs during flexion, extension and rotation based movements potentially increasing your risk of injury (12).
However, one paper found “19-27% of people without symptoms have disc herniation on imaging” (11). A meta-analysis titled “Incidence of Spontaneous Resorption of Lumbar Disc Herniation” found “The overall incidence of spontaneous resorption after LDH was 66.66% (95% CI 51% – 69%)” (16). Yet another paper found “many people without back pain have disk bulges or protrusions but not extrusions. Given the high prevalence of these findings and of back pain, the discovery by MRI of bulges or protrusions in people with low back pain may frequently be coincidental.” (17)
There is also a clear generic component to herniations. This was observed in one paper using an in-vitro model to determine the number of flexion-extension cycles required to cause disc herniation. The number of cycles ranged from 4,400 – 86,400 which demonstrates considerable variation in structural resiliency (18). So although we know that biological factors influence LBP, the presence of tissue damage does not assure the existence of pain. Nor does the existence of pain mean conclusively that tissue damage exists.
Spondylolysis is a defect or stress fracture in the pars interarticularis and is most commonly observed in the low back. Spondylolisthesis is when one of the lower vertebrae slips forward onto the bone directly beneath it. One paper estimates a prevalence of lumbar spondylolysis of 11.5%, of which roughly 25% will experience significant back pain at some point in their lifetime (19). Both conditions are generally classified as being a mechanism for LBP. However, when we review the data including the figures presented above there doesn’t seem to be a significant association to LBP (19).
A common treatment practice for spondylolysis and spondylolisthesis is therapeutic injections of the defect or nerve root. Unfortunately, this approach is used in the absence of any evidence showing it’s utility (19). This is not a stand alone incident either, there are several treatment protocols that have not demonstrated any efficacy and yet they are routinely used by medical practitioners.
Bodyweight is also associated with LBP, with increased BMI and waist to hip ratio correlating with increase risk of LBP (20). However, the association of bodyweight and LBP is unclear and rather weak. One proposed scenario is that excessive bodyweight applies additional stress on the joints and lumbar spine which can lead to CLBP. However, this hypothesis is incongruent with common treatment protocols for obesity which involve the inclusion of resistance training (21). Applying external loads (such as dumbbells) would significantly increase both compressive and sheer forces acting on the joints beyond the individuals bodyweight. However physical exercise has one of the highest success rates for the treatment of LBP (4).
Yet another study found that “both obesity and low level of physical activity are independent risk factors of radiating low back pain…… Moderate level of physical activity is recommended for the prevention of low back pain, especially in obese individuals” (22).
Adipokines are signalling proteins secreted by adipose tissue (23). It’s been observed that obesity increases pro-inflammatory adipokines which can contribute to chronic low grade inflammation (23). Thus, some researchers have associated the pro-inflammatory response to excess adiposity with LBP. Caloric restriction and resistance exercise reduces adiposity and therefore can reduce low grade chronic inflammation. However, if chronic low grade inflammation presented a significant relationship we would see a more homogenous appearance of LBP in overweight and obese subjects which at this point just isn’t reflected in the data.
The Biopsychosocial Pain Model:
Research has demonstrated that biological factors are only one part of a more complex matrix that drives the experience of pain, and as such we can not simply look at pain from a reductionist standpoint. By that I mean, reducing injury down to what is often referred to as a mechanistic view. A succinct description of the biopsychosocial model is “pain is a subjective perception that results from the transduction, transmission, and modulation of sensory input filtered through a person’s genetic composition and prior learning history and modulated further by the person’s current physiological status, current mood state, and sociocultural environment” (24).
This model emphasizes understanding the patients individual situation because their pain is inexplicably linked to their psychology and environment and not just their biology. the model is not new per se but has recently gained more traction as evidence and support from the scientific community begins to grow. The model is complex and contrary to the name pain can not simply be trichotomized (segregated into three distinct groups). All facets of the model are interrelated and it is inappropriate to disassociate one aspect from another.
Lets refer back to lumbar disc herniation as an example. This injury only presents pain symptoms 2-5% of the time; but why is that? In the instances where it incites pain, the common explanation is that the rupture is irritating nerves and is often identified as the pain generator. But if this is the case, why does pain only present itself 2-5% of the time? I’m not saying the biological aspect is untrue, rather it’s a dissociation of biology from the psychocognitive and sociocultural environment aspects of pain.
To further elucidate the psychosocial aspect of pain, we need to discuss the placebo effect. A placebo is essentially anything that appears to be a legitimate medical treatment but isn’t. Often seen as pills, injections, physical therapies and even sham surgeries. A 2019 paper found a 78% reduction in low back pain when given placebo injections (25). This was a randomized, double-blinded, controlled trial and the methods were of high standard suggesting the outcomes are not anomalous.
Participants were advised in advance that they would either be receiving a placebo or a local anesthetic injection. An interesting finding about this intervention was that even the individuals who correctly guessed they were receiving a placebo still experienced a significant reduction in pain. Although larger responses were observed in patients who expected to get the real treatment, this highlights the important roles of expectancy and environment in pain treatment. The environmental factors in this case are numerous, from being involved in a study, receiving an injection and even being educated and monitored by an authority figure (ie. medical professional).
A 2017 systematic review aimed to determine the comparative effect of sham surgeries to actual surgeries in orthopaedics (26). A sham surgery is essentially where a surgeon makes an incision then sutures it without performing any surgical intervention. The paper found “sham surgery has shown to be just as effective as actual surgery in reducing pain and disability” (26). Once again this is due to several interrelated factors and it’s inappropriate to attempt to distil it down to a single mechanism. This should not be interpreted to mean that the biological aspect of pain is “just in your head”. As I mentioned previously, the biological, psychocognitive and social aspects are interrelated and the aim should not be to disassociate them in order to reduce it down to a single causal factor.
Fear avoidance refers to the conscious avoidance of physical activities that are expected to induce pain. A 2009 paper looking at fear avoidance beliefs as a predictor of low back pain found “fear-avoidance beliefs are present before the initiation of LBP and that fear-avoidance beliefs are developed in a reciprocal process with the LBP pain experience” (27). Essentially individuals who deem certain movements or activities as dangerous are more likely to experience pain when performing those movements or activities. Another study looking at occupational health guidelines found “low back pain is a self limiting condition and…… remaining at work or an early (gradual) return to work, if necessary with modified duties, should be encouraged and supported” (28). This guideline is also applicable to the return to sports, lifting weights etc. In fact several studies on the subject of fear avoidance emphasizes the continuation of daily activities to prevent it’s occurrence and significance (29)
Decreased activity due to fear avoidance beliefs is also associated with transition of acute LBP to chronic LBP and prolonged disability (30). Vlaeyen and colleagues have developed a treatment approach for fear avoidance similar to cognitive behavioural treatment for phobias (31). This approach develops a hierarchical model of feared behaviours which the participant proceeds to voluntarily expose themselves to as they move up the hierarchy. This process allows the individual to challenge their beliefs on the dangers of specific movements or activities. For example, if an individual is afraid to carry their groceries from the car to their front door, a clinician may suggest they perform that activity repeatedly. Through pain free exposure they are able to overcome their perception of danger and pain associated with that particular task (31).
Obstacles To Effective Treatment Of Pain:
There are significant obstacles to effective treatment of pain, one of which is the patients perspective and buy in to the cause and treatment being espoused. This is in part due to the practitioners inability to correctly educate or disseminate information in a method that is easily understood and accepted by the patient (which by the way is no easy task). The spread of misinformation through various channels presents even more obstacles. In 2018 researchers conducted a study to observe the proliferation of true and false news online. The researchers found “the top 1% of false news cascades diffused to between 1000 and 100,000 people, whereas the truth rarely diffused to more than 1000 people. Falsehood also diffused faster than the truth. The degree of novelty and the emotional reactions of recipients may be responsible for the differences observed” (32).
Research lead by Adrien Friggeri discovered 45% of rumours on Facebook were determined to be false (33). In an attempt to discover factors related to a patients rejection of medical advice from qualified licensed professionals, researchers found “One significant cause of suboptimal utilization of our prodigious tool chest is medical misinformation hyped through the internet, television, chat rooms, and social media. In many instances, celebrities, activists, and politicians convey false information; not uncommonly, authors with purely venal motives participate” (34)
This highlights the importance of an individuals perspective on pain and effective treatment approaches. This comes back to the psychocognitive and sociocultural aspects of pain. Therefore it is important to re-educate individuals to gain patient buy in. The types of conversations that ensue are also critical, since effective communication is predicated on understanding and not necessarily on how accurately you articulate a concept. What you communicate is important, but the purpose of communication is the successful transmission of information. Although clear and concise speaking is closely tied to accurate transmission of information it does not guarantee it. As the expression goes seek first to understand (the patient), then to be understood (the patients situation and potential solution).
The deeply rooted biomedical culture amongst physicians is also an obstacle to pain management. Some practitioners simply have outdated information, and still others who are aware of the biopsychosocial model are reluctant to adopt the shift in scientific understanding. This is often the case with significant paradigm shifts, but as more information emerges I’m confident a more comprehensive and inclusive biopsychosocial model will become the predominant approach to pain.
Exercise As A Treatment Method For Low Back Pain:
Research has demonstrated that physical activity improves all aspects of quality of life (35). Since quality of life is subjective it means the benefits of physical activity are multi-dimensional and contextualized based on individual settings. As one study found “There appears to be a graded linear relation between the volume of physical activity and health status, such that the most physically active people are at the lowest risk” (36).
A systematic review and meta-analysis published in 2014 found strength training led to a reduction in injuries by over 66% and overuse injuries were reduced by almost 50% (37). This is due to increased proprioceptive awareness and resiliency of the tissue. We may now refer back to the clinical definition of injury by which a tissue is taken beyond it’s functional loading capacity. By increasing strength, we simultaneously increase the tissues functional loading threshold. One 2018 systematic review found a dose response relationship between volume/intensity and injury prevention with higher volumes and intensities resulting in a stronger protective effect (38).
This effectiveness of this relationship assumes appropriate prescription of volume and intensity within the program design, thus allowing for sufficient recovery. Some of the protective features of strength training are thought to be related to improved motor control and stabilization, improved trunk stability and a refined ability to identify high-risk situations and select an appropriate course of action (38).
A network meta-analysis is a study “in which multiple treatments (that is, three or more) are being compared using both direct comparisons of interventions within randomized controlled trials and indirect comparisons across trials based on a common comparator” (39). This allows researchers to gain a unique perspective on the comparative performance of various treatment outcomes.
One network meta-analysis set out to determine which specific exercise protocols were most effective in treating low back pain. Although it’s unlikely that one particular exercise intervention is the single best prescription for pain management, research indicates that physically active therapies tend to be the most efficacious (4).
This paper found that specifically “pilates, resistance, stabilization/motor control and aerobic exercise training….. are the most effective” at reducing pain (4). This is likely due to several overlapping factors including but not limited to increased muscular strength, resiliency, coordination, stabilization, confidence and an altered perspective resulting from exposure to physical activity to reduce catastrophizing and fear avoidance. In improving physical function, pilates, water based and aerobic exercise had a significant impact (4). The diversity of exercise protocols demonstrates the variability in potential treatments for CLBP, and suggests inter-individual differences need to be considered when selecting the appropriate intervention.
With regard to improving mental health aerobic and resistance training were identified as most likely to generate improvement (4). As one paper found, mental health issues were observed to affect up to 36% of individuals with CLBP (40). This is unsurprising considering the reciprocal relationship between depression, anxiety and chronic pain in general (40). When looking at pain through the scope of self determination theory, autonomy and competency may also influence the pain experience. If an individual does not feel in control or capable of improving their situation this can make pain management far more challenging. This is also why I recommend seeking help from a qualified professional which on its own may help alleviate feelings of helplessness.
Trunk musculature plays a role in the management and reduction of CLBP symptoms, however the extent is not fully understood. What is known however is that trunk strength and endurance seem to play a role in reduction of perceived pain (41)(42)(43). A deconditioning of the spinal extensors is observed in individuals with LBP. Therefore, exercise interventions that involve some form of trunk strengthening along with stabilization and motor control activities are beneficial in pain management.
In summary, based on the available research exercise in general appears to be a highly effective approach to pain management and reduction. Pilates, resistance training and stabilization/motor control exercises appear to be the most efficacious. It’s unlikely that one single exercise approach will be the best solution for every individual. As such exercise prescription should consider inter-individual differences and preferences, with the aim of progression in volume and intensity at a rate appropriate for the individual.
Although exercise has a high performance rate in the treatment of pain, I want to reiterate that disassociation between biological, psychological and social aspects of the pain experience should be avoided. Rather, all factors should be regarded as an interconnected network that feed into one another to create the pain experience. For instance, the mere fact of participation in a rehabilitative program may be enough to meaningly reduce pain symptoms for some individuals. The aim should be to understand the patients pain through the psychocognitive, biophysical and sociological lens simultaneously.
If you would like help from a qualified professional I would recommend visiting https://www.clinicalathlete.com/clinicians. Clinical Athlete was founded by Dr. Quinn Henoch (a doctor of physical therapy) to help individuals find licensed practitioners of various disciplines who have an integrated understanding of pain, health, fitness and athletic performance. Good luck!