title: Alternating activation is related to fatigue in lumbar muscles during sustained sitting.
abstract: The aim of this study was to investigate the relation between variability in muscle activity and fatigue during a sustained low level contraction in the lumbar muscles. Twenty-five healthy participants (13 men 12 women) performed a 30min sitting task with 5 degrees inclination of the trunk. Surface electromyographic (EMG) signals were recorded bilaterally from the lumbar muscles with 2 high density surface EMG grids of 9×14 electrodes. Median frequency (MDF) decrease, amplitude (RMS) increase and the rating of perceived exertion (RPE) were used as fatigue indices. Alternating activation and spatial and temporal variability were computed and relations with the fatigue indices were explored. During sitting, the mono- and bipolar RMS slightly increased while the MDF remained unchanged indicating no systematic muscle fatigue, although the average RPE increased from 6 to 13 on a scale ranging between 6 and 20. Higher frequency of alternating activation between the left and right side was associated with increased RPE (p=0.03) and decreased MDF (p=0.05). A tendency in the same direction was seen between increased spatial and temporal variation within the grids and increased RPE and decreased MDF. Present findings provide evidence for a relationship between variability in muscle activity and fatigue.
authors.affiliation: Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway; Clinic Physical Medicine and Rehabilitation, Vestfold Hospital Trust, Stavern, Norway. Electronic address: inge.ringheim@siv.no.
authors.forename: Inge
authors.initials: I
authors.lastname: Ringheim
authors.affiliation: Clinic Physical Medicine and Rehabilitation, Vestfold Hospital Trust, Stavern, Norway.
authors.forename: Aage
authors.initials: A
authors.lastname: Indahl
authors.affiliation: Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Karin
authors.initials: K
authors.lastname: Roeleveld
mesh_terms: D000328:Adult; D064131:Back Muscles / Q000000981:diagnostic imaging / Q000502:physiology*; D001711:Biotransformation / Q000502:physiology; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008161:Lumbosacral Region / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011795:Surveys and Questionnaires; D014463:Ultrasonography
keywords: Alternating activation; HDsEMG; Low back; Muscle fatigue; Submaximal contraction