Contents lists available at ScienceDirect Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech The effect of extensible and non-extensible lumbar belts on trunk muscle activity and lumbar stiffness in subjects with and without low-back pain Daniel Ludvig a, ⁎ ,1 , Richard Preuss a,b , Christian Larivière a,c a Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, QC, Canada b School of Physical & Occupational Therapy, McGill University, Montréal, QC, Canada c Occupational Health and Safety Research Institute Robert-Sauvé, Montréal, QC, Canada ARTICLE INFO Keywords: Lumbar belts Spinal stability Lumbar stiffness Trunk muscle activity Low-back pain ABSTRACT Background: Lumbar belts have been shown to increase lumbar stiffness, but it is unclear if this is associated with trunk muscle co-contraction, which would increase the compression on the spine. It has been hypothesized that lumbar belts increase lumbar stiffness by increasing intra-abdominal pressure, which would increase spinal stability without increasing the compressive load on the spine. Methods: Trunk muscle activity and lumbar stiffness and damping were measured in healthy and low-back pain subjects during three conditions: no lumbar belt; wearing an extensible lumbar belt; wearing a non-extensible lumbar belt. Muscle activity was measured while subjects performed controlled forward and backward 20° trunk sways. Lumbar stiffness and damping were measured by applying random continuous perturbation to the chest. Findings: External oblique activity was decreased when wearing either lumbar belt during all phases of move- ment, while rectus abdominis and iliocostalis activity were decreased during the phase of movement where the muscles were maximally active while wearing either belt. Trunk stiffness was greatly increased by wearing either belt. There were no consistent differences in either lumbar stiffness or muscle activity between the two belts. Wearing a lumbar belt had little to no effect on damping. There were no group differences in any of the measures between healthy and low-back pain populations. Interpretation: The findings are consistent with the hypothesis that lumbar belts can increase spinal stability by increasing intra-abdominal pressure, without any increase in the compressive load on the spine. The findings can also be generalized, for the first time, to subjects with low-back pain. 1. Introduction Low-back pain (LBP) has been recognized as a leading cause of disability worldwide (Hoy et al., 2012). One common therapy used in the treatment of LBP is lumbar belts (LBs). Though reviews of numerous studies have found no evidence of LBs preventing a first occurrence of LBP (Jellema et al., 2001; van Duijvenbode et al., 2008; Verbeek et al., 2011), the contribution of LBs in reducing the pain and disability of patients with LBP remains unclear (Jellema et al., 2001; van Duijvenbode et al., 2008). One potential mechanism for the action of LBs in the prevention or reduction of LBP is an increase in lumbar stability. Insufficient lumbar stability has been shown to be a major contributor to LBP (Panjabi, 2003). Biomechanical models have shown that insufficient lumbar stiffness, a surrogate measure of lumbar stability, can lead to injury and LBP (Cholewicki and McGill, 1996). Experimentally, it has been seen that patients with LBP display increased lumbar stiffness (Hodges et al., 2009; Miller et al., 2013), which is likely due to different muscle acti- vation strategies to enhance lumbar stability (van Dieën et al., 2003). LBs have been shown to increase lumbar stiffness as well (Cholewicki et al., 1999b; Ivancic et al., 2002; Lavender et al., 2000; McGill et al., 1994), though recent studies show conflicting results with regard to the efficiency of different flexible LBs (extensible vs non-extensible) (Cholewicki et al., 2010; Larivière et al., 2014). It is hypothesized that LBs increase lumbar stiffness by increasing intra-abdominal pressure (van Poppel et al., 2000). Normally, intra- abdominal pressure can be increased by co-contraction of the abdom- inal and back muscles (Cholewicki et al., 1999a). Increased abdominal pressure helps to extend the trunk, which in turn reduces the activation of the back muscles and lumbar compression (Stokes et al., 2010). https://doi.org/10.1016/j.clinbiomech.2019.04.019 Received 21 January 2019; Accepted 28 April 2019 ⁎ Corresponding author at: Department of Biomedical Engineering, Northwestern University, 2145 N Sheridan Road, Evanston, IL 60208, USA. E-mail address: daniel.ludvig@mail.mcgill.ca (D. Ludvig). 1 Present affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA; Shirley Ryan AbilityLab, Chicago IL, USA. Clinical Biomechanics 67 (2019) 45–51 0268-0033/ © 2019 Elsevier Ltd. All rights reserved. T