title: Age-related changes in trunk neuromuscular activation patterns during a controlled functional transfer task include amplitude and temporal synergies.
abstract: While healthy aging is associated with physiological changes that can impair control of trunk motion, few studies examine how spinal muscle responses change with increasing age. This study examined whether older (over 65 years) compared to younger (20-45 years) adults had higher overall amplitude and altered temporal recruitment patterns of trunk musculature when performing a functional transfer task. Surface electromyograms from twelve bilateral trunk muscle (24) sites were analyzed using principal component analysis, extracting amplitude and temporal features (PCs) from electromyographic waveforms. Two PCs explained 96% of the waveform variance. Three factor ANOVA models tested main effects (group, muscle and reach) and interactions for PC scores. Significant (p<.0125) group interactions were found for all PC scores. Post hoc analysis revealed that relative to younger adults, older adults recruited higher agonist and antagonistic activity, demonstrated continuous activation levels in specific muscle sites despite changing external moments, and had altered temporal synergies within abdominal and back musculature. In summary both older and younger adults recruit highly organized activation patterns in response to changing external moments. Differences in temporal trunk musculature recruitment patterns suggest that older adults experience different dynamic spinal stiffness and loading compared to younger adults during a functional lifting task.
authors.affiliation: School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada; School of Health and Human Performance, Dalhousie University, Halifax, NS, Canada.
authors.forename: D Adam
authors.initials: DA
authors.lastname: Quirk
authors.affiliation: School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada; School of Health and Human Performance, Dalhousie University, Halifax, NS, Canada; School of Physiotherapy, Dalhousie University, Halifax, NS, Canada. Electronic address: cheryl.kozey@dal.ca.
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Hubley-Kozey
mesh_terms: D000009:Abdominal Muscles / Q000503:physiopathology; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D000886:Anthropometry; D004576:Electromyography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017116:Low Back Pain / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009068:Movement; D018482:Muscle, Skeletal / Q000502:physiology*; D025341:Principal Component Analysis; D013997:Time Factors; D014741:Video Recording; D055815:Young Adult
keywords: Aging differences; Bidirectional moment; Electromyography; Muscle synergies; Temporal patterns; Trunk musculature