Age-related changes in trunk neuromuscular activation patterns during a controlled functional transfer task include amplitude and temporal synergies

•Older adults did not have systematically higher activation amplitudes for all trunk muscles sites.•Older adults had less temporal adjustment in abdominal site activation to changing external loads.•Older adults had altered temporal synergies among specific abdominal and back extensor sites.•Sustained activity and altered synergies imply dynamic spinal load pattern changes with age. 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 65years) compared to younger (20–45years) 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