title: Are regions of the lumbar multifidus differentially activated during walking at varied speed and inclination?
abstract: OBJECTIVE
  Lumbar multifidus is a complex muscle with multi-fascicular morphology shown to be differentially controlled in healthy individuals during sagittal-plane motion. The normal behaviour of multifidus muscle regions during walking has only received modest attention in the literature. This study aimed to determine activation patterns for deep and superficial multifidus in young adults during walking at different speeds and inclination.
  
  
  METHODS
  This observational cohort study evaluated ten healthy volunteers in their twenties (three women, seven men) as they walked on a treadmill in eight conditions; at 2km/h and 4km/h, each at 0, 1, 5, and 10% inclination. Intramuscular EMG was recorded from the deep and superficial multifidus unilaterally at L5. Activity was characterized by: amplitude of the peak of activation, position of peak within the gait cycle (0-100%), and duration relative to the full gait cycle.
  
  
  RESULTS
  Across all conditions superficial multifidus showed higher normalised EMG amplitude (p<0.01); superficial multifidus peak amplitude was 232±115% higher when walking at 4km/h/10%, versus only 172±77% higher for deeper region (p<0.01). The percentage of the gait cycle where peak EMG amplitude was detected did not differ between regions (49±13%). Deep multifidus duration of activation was longer when walking at the faster vs slower speed at all inclinations (p<0.01), which was not evident for superficial multifidus (p<0.05). Thus, a significantly longer activation of deep multifidus was observed compared to superficial multifidus when walking at 4km/h (p<0.05).
  
  
  CONCLUSIONS
  Differential activation within lumbar multifidus was shown in young adults during walking. The prolonged, more tonic activation of deep relative to superficial regions of multifidus during gait supports a postural function of deeper fibres.
authors.affiliation: Institute for Health Sciences, Zürich University of Applied Sciences, Technikumstrasse 71, Winterthur 8401, Switzerland; Faculty of Health Professions, Curtin University, Kent Street, Perth 6102, Australia. Electronic address: rebecca.crawford@zhaw.ch.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Crawford
authors.affiliation: Institute of Neurorehabilitation Systems, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany. Electronic address: leonardo.gizzi@bccn.uni-goettingen.de.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Gizzi
authors.affiliation: Institute for Health Sciences, Zürich University of Applied Sciences, Technikumstrasse 71, Winterthur 8401, Switzerland. Electronic address: aine.nimhuiris@zhaw.ch.
authors.forename: Áine Ni
authors.initials: ÁN
authors.lastname: Mhuiris
authors.affiliation: School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, UK. Electronic address: d.falla@bham.ac.uk.
authors.forename: Deborah
authors.initials: D
authors.lastname: Falla
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008161:Lumbosacral Region / Q000502:physiology*; D008297:Male; D064170:Paraspinal Muscles / Q000294:innervation / Q000502:physiology*; D000072797:Walking Speed
keywords: Function; Gait; Intramuscular electromyography; Lumbar spine; Multifidus