It is important to increase our understanding of the mechanisms underlying the transition from acute to chronic non-specific low back pain (NSLBP) to improve treatments for NSLBP and individual treatment decisions in an early phase of low back pain and ultimately to prevent the development of chronic NSLBP. Dutch physiotherapy guidelines for NSLBP (Staal et al., 2017) recommend different treatments depending on the course of the lower back pain and the presence or absence of psychosocial risk factors (e.g. pain-related fear, somatization, depressive complaints and psychological distress). Education and/or exercise therapy are recommended when psychosocial risk factors are absent. When psychosocial risk factors are present a more cognitive-behavioural approach is recommended with the application of ‘graded activity’ or ‘graded exposure’ approaches. A widely used screening tool for patients with acute NSLBP is the STarT back tool (Hill et al., 2008; Hill et al., 2011). The STarT allocates patients with acute NLSBP in three groups, according to the estimated risk to develop chronic NSLBP (e.g. low, medium, and high risk). Scores on the STarT immediately give potentially modifiable treatment indicators. For example, patients classified at low risk would receive only advice and education (i.e. standard best-practice). Patients classified at medium risk would be suitable for physiotherapy, and patients classified at high risk would be suitable for a combination of physiotherapy and cognitive-behavioural approaches (Hill et al., 2008; Hill et al., 2011).
Both the Dutch guideline for physiotherapists (Staal et al., 2017) and the STarT (Hill et al., 2008; Hill et al., 2011) are partly based on assumptions made in the fear-avoidance model. In the ‘avoidance’ pathway, individuals have negative appraisals about pain and its potential consequences. This induces prioritization of behaviour aimed at controlling pain, leading to pain-related fear and avoidance of activities that are expected to be painful (Vlaeyen et al., 2016). Although adaptive in the acute phase, exaggerated or persistent avoidance of feared activities may paradoxically lead to functional disability. Exaggerated avoidance can lead to physical inactivity (e.g. disuse) and mental problems (e.g. mood disturbances, irritability, depression). However, fear avoidance is not the only behavioural pathway leading to chronic pain. The avoidance-endurance model (AEM) of pain postulates an additional pathway through ‘endurance responses’ in which overuse and overload of physical structures eventually lead to chronic pain (Hasenbring, 2000). The AEM distinguishes 2 types of ‘endurers’, namely: distress-endurers (DE), who tend to have more pessimistic thoughts and feel more negative, and eustress-endurers (EER), characterized by positive mood and distraction despite having pain. The avoidance-endurance questionnaire (AEQ) is a reliable and valid measure to assess the pattern of response: fear-avoidance response (FAR) or endurance response (ER) (Hasenbring, Hallner and Rusu, 2009). Hasenbring et al. (2012) used the AEQ to classify a group of 177 subacute NSLBP patients and classified 19.2% of the patients with distress-endurance responses, 16.4% with eustress-endurance responses, and 9.6% with fear avoidance responses. The remaining 54.8% showed an adaptive response to subacute pain characterized by a healthy balance between avoidance and endurance responses. This finding highlights the importance of endurance responses, because the majority of maladaptive responses are characterized by endurance instead of fear avoidance (i.e. 35.6% vs 9.6%).
To select the best (physiotherapeutic) treatment strategy for (sub)acute NSLBP it is important to know whether fear avoidance and endurance responses have differential effects on physical structures in the lower back (and adjacent regions). In a comprehensive review, Hasenbring (2020) explains the differential neuromuscular effects between FAR and ER. According to Hasenbring (2020), inactive, avoidant behaviour would drive disuse-related muscle weakness, deconditioning, and metabolic changes in the musculoskeletal structures and the central nervous system, leading to peripheral and central sensitization and increased pain perception. In contrast, in overactive behaviour, inadequate muscle forces might expose mainly passive structures (vertebral joints, ligaments, connective tissue) to increased stress and repetitive strain, causing microdamage, laxity, and inflammation. In the long-term, this process would also lead to peripheral and central sensitization through repetitive tissue strains. To date, there are few studies comparing the behavioural patterns in response to pain (e.g. avoidance responses vs endurance responses) with respect to objective movement related outcomes. Future studies should focus on unravelling the differences in neuromuscular adaptations between the different response patterns to pain (FAR, ER, AR) to better understand which specific treatment has to be selected per individual with NSLBP. Also, it is important to raise awareness among health care professionals about the AEM when they are regularly confronted with NSLBP patients in the (sub)acute phase. They could use this framework to select individuals who are at high risk for developing persistent low back pain and adjust their treatment decisions accordingly. Further, it is of critical importance that behavioural change is stimulated already in the (sub)acute phase before acute pain turns into persistent pain.
Psychosomatic psychologist at Rughuis, Roermond, The Netherlands and PhD researcher at the Spine, Head and Pain Research Unit, Ghent University, Belgium.
2020Pain in Motion
References and further reading:
Hasenbring, M. (2000). Attentional control of pain and the process of chronification. In Progress in brain research (Vol. 129, pp. 525-534). Elsevier.
Hasenbring, M. I., Andrews, N. E., & Ebenbichler, G. (2020). Overactivity in Chronic Pain, the Role of Pain-related Endurance and Neuromuscular Activity: An Interdisciplinary, Narrative Review. The Clinical Journal of Pain, 36(3), 162-171.
Hasenbring, M. I., Hallner, D., Klasen, B., Streitlein-Böhme, I., Willburger, R., & Rusche, H. (2012). Pain-related avoidance versus endurance in primary care patients with subacute back pain: psychological characteristics and outcome at a 6-month follow-up. Pain, 153(1), 211-217.
Hasenbring, M. I., Hallner, D., & Rusu, A. C. (2009). Fear-avoidance-and endurance-related responses to pain: development and validation of the Avoidance-Endurance Questionnaire (AEQ). European Journal of Pain, 13(6), 620-628.
Hill, J. C., Dunn, K. M., Lewis, M., Mullis, R., Main, C. J., Foster, N. E., & Hay, E. M. (2008). A primary care back pain screening tool: identifying patient subgroups for initial treatment. Arthritis Care & Research: Official Journal of the American College of Rheumatology, 59(5), 632-641.
Hill, J. C., Whitehurst, D. G., Lewis, M., Bryan, S., Dunn, K. M., Foster, N. E., . . . Somerville, S. (2011). Comparison of stratified primary care management for low back pain with current best practice (STarT Back): a randomised controlled trial. The Lancet, 378(9802), 1560-1571.
Staal, J., Hendriks, E., Heijmans, M., Kiers, H., Lutgers-Boomsma, A., Rutten, G., . . . Custers, J. (2017). KNGF-richtlijn Lage rugpijn: update klinimetrie. Amersfoort: Koninklijk Nederlands Genootschap voor Fysiotherapie.
Vlaeyen, J. W., Crombez, G., & Linton, S. J. (2016). The fear-avoidance model of pain. Pain, 157(8), 1588-1589.