Exploring the clinical utility of myotonometry to identify neuromuscular impairments in individuals with low back pain.

Low back pain (LBP) is one of the most reported musculoskeletal disorders amongst adults. Identifying LBP-related impairments with reliable and valid clinical measures is recommended to improve clinical decisions and rehabilitation outcomes. Myotonometry is an objective method to reliably quantify the property of muscle stiffness through portable, handheld devices. Individuals with LBP have demonstrated increased stiffness in lumbar musculature, but this has only been determined under limited conditions (prone and/or relaxed). The aim of these studies was to determine the test-retest reliability of myotonometry in lumbar (lumbar multifidus [LM], longissimus thoracis [LT]) and thigh (vastus lateralis [VL], biceps femoris [BF]) musculature with participants in standing and deadlifting postures. Secondly, a cross-sectional design was used to compare stiffness of the LM, LT, VL, and BF muscles of individuals with and without LBP across standing and deadlifting postures. Intraclass correlation coefficients (ICC3,2) of the stiffness measures were good to excellent in all muscles across the standing position ( ICCs: VL = 0.94 [0.87-0.97], BF = 0.97 [0.93-0.98], LM = 0.96 [0.91-0.98], LT = 0.81 [0.59-0.91], and were excellent in all muscles across the deadlifting position (ICCs: VL = 0.95 [0.89-0.98], BF = 0.94 [0.87-0.97], LM = 0.96 [0.92-0.98], LT = 0.93 [0.86-0.97]). Within the deadlift condition there was a significantly greater increase in the percent-muscle stiffness change that occurred in the VL (p = .029, 21.9%) and BF (p = .024, 11.2%) muscles for the control group. There were no differences in percent-muscle stiffness changes for the standing condition nor were there any absolute muscle stiffness differences between the two groups for the standing or deadlifting conditions. These results may expand the research and clinical applications of myotonometry to identify muscular deficits and track intervention effectiveness. Future studies should seek to expand on these findings by using myotonometry to further investigate the relationships between muscle stiffness and deadlift performance in LBP populations of varying degrees of pain and disability.