title: Effect of acute noxious stimulation to the leg or back on muscle synergies during walking.
abstract: This study aimed to examine how acute muscle pain affects muscle coordination during gait with consideration of muscle synergies (i.e., group of muscles activated in synchrony), amplitude of muscle activity and kinematics. A secondary aim was to determine whether any adaptation was specific to pain location. Sixteen participants walked on a treadmill during 5 conditions [control, low back pain (LBP), washout LBP, calf pain (CalfP), and washout CalfP]. Five muscle synergies were identified for all of the conditions. Cross-validation analysis showed that muscle synergy vectors extracted for the control condition accounted for >81% of variance accounted for from the other conditions. Muscle synergies were altered very little in some participants (n = 7 for LBP; n = 10 for CalfP), but were more affected in the others (n = 9 for LBP; n = 6 for CalfP). No systematic differences between pain locations were observed. Considering all participants, synergies related to propulsion and weight acceptance were largely unaffected by pain, whereas synergies related to other functions (trunk control and leg deceleration) were more affected. Gastrocnemii activity was less during both CalfP and LBP than control. Soleus activity was further reduced during CalfP, and this was associated with reduced plantar flexion. Some lower leg muscles exhibited adaptations depending on pain location (e.g., greater vastus lateralis and rectus femoris activity during CalfP than LBP). Overall, these changes in muscle coordination involve a participant-specific strategy that is important to further explore, as it may explain why some people are more likely to develop persistence of a painful condition.
authors.affiliation: The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitations Sciences, St. Lucia, Brisbane, Queensland, Australia; w.vandenhoorn@uq.edu.au.
authors.forename: Wolbert
authors.identifier: http://orcid.org/0000-0002-9658-2388
authors.initials: W
authors.lastname: van den Hoorn
authors.affiliation: The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitations Sciences, St. Lucia, Brisbane, Queensland, Australia;
authors.forename: Paul W
authors.initials: PW
authors.lastname: Hodges
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia;
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
authors.affiliation: The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitations Sciences, St. Lucia, Brisbane, Queensland, Australia; University of Nantes, Laboratory "Motricité, Interactions, Performance" (EA 4334), Nantes, France.
authors.forename: François
authors.identifier: http://orcid.org/0000-0002-6432-558X
authors.initials: F
authors.lastname: Hug
mesh_terms: D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D007866:Leg / Q000503:physiopathology*; D017116:Low Back Pain / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology*; D063806:Myalgia / Q000503:physiopathology*; D010812:Physical Stimulation; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: experimental pain; gait; motor modules; muscle coordination; nonnegative matrix factorization