TRUNK ISOKINETIC STRENGTH AND ENDURANCE IN TWO GROUPS OF PEOPLE WITH CHRONIC LOW BACK PAIN: A LONGITUDINAL RETROSPECTIVE STUDY

M. Coleman¹, J. Linères¹, C. Théry¹, G. Adrien¹, C. Daste², F. Rannou², C. Nguyen², M.-M. Lefèvre-Colau², A. Rören³

¹AP-HP, Hôpital Cochin, Rehabilitation Department, Paris, France, ²Université Paris Cité, Faculty of Medicine, Paris, France, ³Hôpital Cochin, Rehabilitation Department, Paris, France

Background: Chronic low back pain (CLBP) has been associated with physical and psychosocial deconditioning factors. Physical deconditioning is characterized by decreased strength and endurance of the trunk muscles, particularly affecting the extensor muscles. Multidisciplinary functional restoration programs (FRPs) aimed to improve physical, psychological and social flaws associated with CLBP and to facilitate the return to work. Different types of FRPs have been proposed that vary in intensity and content.

Purpose: To assess the variation of trunk isokinetic muscle strength and endurance after 2 different multidisciplinary functional restoration programs: intensive (IFRP) (175 hours including 125h of physical activity), and the semi-intensive program (SIFRP) (40 hours including 32h of physical activity) in people with CLBP.

Methods: Longitudinal single-center retrospective study. Isokinetic tests were performed to assess trunk flexors and extensors muscular strength (60° s^-1) and endurance (120°.s^-1) using the Humac NORM isokinetic dynamometer. The primary outcome was the variation of isokinetic scores (peak, total work and flexors/extensors ratio) after the program assessed by paired t-test (p<0.05). The secondary outcomes were the variation of clinical scores. The association between demographic characteristics (sex, age) and the variation of isokinetic (peak torque and total work) and clinical scores of interest (low back pain, activity limitation, scores of anxiety and depression and fear and avoidance beliefs regarding work and physical activity) was assessed using Pearson’s rho and multiple linear regression (dependent factor: variation in isokinetic extensors endurance).

Results: The participants were 64 [women 73.5%; 45.3 (11.2) years, 24.3 (4.5) kg.m^-2] in the SIFRP and 61 [women 52.5%; 41.7(9) years; 25.9 (5.1) kg.m^-2]. Trunk extensors peak torque (+13.8%, and +11%), total work for extensors (+13.2% and +26.3%) and flexors (+7.1% and +14.6%) and peak flexors/extensors ratio (-13.5% and -8.1%) significantly improved in the SIFRP and IFRP group respectively, p<0.001. The greater significant variations were for trunk extensors endurance in the IFRP group. Activity limitation, anxiety and depression significantly improved in both groups. Correlations between variations in isokinetic and clinical parameters were low to moderate in the SIFRP and low in the IFRP group. None of the selected variable significantly predicted improvement in extensors total work in any group.

Conclusions: Our study shows significant short-term improvements for trunk extensors strength and flexors and extensors endurance in both groups. The higher amount of variation was for trunk extensors endurance for participants that participated in the more intensive program. In both groups, the variation of isokinetic and clinical parameters seemed independent highlighting the need for multidisciplinary rehabilitation.

Implications: The remaining pain and fear and avoidance beliefs regarding work require longer participants’ management and follow-up, supported by a stronger interaction with the work environment, especially for people disengaged from professional activity. We need to investigate the dose effect of FRPs according to the patient’s phenotype in order to propose more personalized rehabilitation programs.

Funding acknowledgements: No funding

Keywords:
Isokinetic
Functional restoration program
Chronic low back pain

Topics:
Musculoskeletal: spine
Pain & pain management
Rheumatology

Did this work require ethics approval? No

Reason: The study was conducted in accordance with the principles of the Helsinki Declaration and the rules of good clinical practice. All patients were informed by our institution that their personal data, routinely collected as part of administrative and healthcare management processes, could be used for research purposes in the field of health, and provided written informed consent. Because patients' data were retrospectively retrieved from medical charts, formal approval by an institutional review board was not required according to the French Law of March 5, 2012 and its application decree (No. 2016-1537) for research involving humans in France.