TITLE: Lumbar Kinematic Pattern Variability during Gait and the Effects of Isolated Lumbar Extension Exercise in Chronic Low Back Pain

Chronic low back pain (CLBP) is a multifactorial condition with a variety of symptoms; one being gait variability. The lumbar spine and its musculature are important in controlling gait and in CLBP the lumbar extensors are often deconditioned. Because of this specific exercise for the lumbar extensors is often recommended. It was therefore of interest to examine relationships between lumbar kinematic variability during gait, with pain, disability and isolated lumbar extension (ILEX) strength in CLBP participants in addition to the effects of a 12 week intervention of ILEX exercise upon these variables. Twenty four CLBP participants were assessed for lumbar kinematics during gait, ILEX strength, pain (VAS), and disability (ODI) pre and post a 12 week intervention. Kinematic variability has been previously examined using Winter’s coefficient of variation (CV). We utilised novel methods of differentiating waveform pattern (CVp) and offset (CVo) variability for comparison. Participants were randomised to either a training group undergoing 12 weeks of ILEX exercise 1x/week or a non-training control. Examination of Winters CV, CVp and CVo showed they incorporate largely different sources of variability and that CVp best represents motor repeatability. Baseline comparisons also showed kinematic variables differed across movement planes; displacement and Winter’s CV highest and similar in frontal and transverse planes, and CVp and CVo higher in the sagittal plane compared to frontal and transverse planes which were similar. Spearman’s correlations of baseline data showed significant correlations between transverse plane CVp and ILEX strength (r = -.411) and ODI (r = .401). However, VAS was not correlated with CVp in any plane. These findings contrast with earlier studies utilising Winter’s CV. CVp instead suggests that highest variability occurs in sagittal plane movement during gait in CLBP. After the ILEX intervention the training group showed a significant reduction in sagittal plane CVp (-20.90+43.53%) indicating improved motor pattern replication. Considering the role of the lumbar extensors in gait, the relationship between both ILEX strength and ODI with transverse plane CVp suggests gait variability may result in consequence of lumbar extensor deconditioning or disability accompanying CLBP. The ILEX intervention however appeared to specifically improve sagittal plane variability perhaps due to the plane of movement utilised during the exercise.