Abstract
BackgroundAgeing may cause impairments in executing bilateral movement control. This study investigated age-related changes in interlimb force coordination across multiple trials by quantifying bilateral motor synergies based on the uncontrolled manifold hypothesis. Participants completed the trials with and without visual feedback.MethodsTwenty healthy individuals (10 older adults and 10 young adults) performed 12 isometric force control trials for the two vision conditions at 5% of maximal voluntary contraction. All dependent variables were analyzed in two-way mixed model (Group × Vision Condition; 2 × 2) ANOVAs with repeated measures on the last factor.ResultsThe analyses revealed that older adults had greater mean force produced by two hands in both vision conditions (i.e., yes and no visual feedback). Across both vision conditions, the older adult group showed greater asymmetrical force variability (i.e., standard deviation of non-dominant hand > standard deviation of dominant hand) and revealed more positive correlation coefficients between forces produced by two hands as compared with the young adult group. Finally, an index of bilateral motor synergies was significantly greater in young adults than older adults when visual feedback was available.ConclusionThe current findings indicate that deficits in interlimb force coordination across multiple trials appeared in older adults.
Highlights
Ageing may cause impairments in executing bilateral movement control
Mean force, force variability, and asymmetry between hands The two-way mixed ANOVA on mean force produced by two hands revealed a significant Group × Vision Condition (2 × 2) interaction [F (1,18) = 10.75; P = 0.004; partial η2 = 0.37; Table 1]
Post hoc analysis indicated that mean force in the older adult group was significantly higher in the no vision condition than the vision condition (P = 0.003) whereas no significant changes in mean force appeared in the young adult group (P = 0.25)
Summary
Ageing may cause impairments in executing bilateral movement control. Ageing typically causes deficits in executing and controlling various movements of the upper extremities because of physiological alterations in the neuromuscular system [1, 2]. Upper limb dysfunction in older adults interferes with activities of daily living and may be an index for motor and cognitive impairments [3,4,5]. Interlimb coordination, executing cooperative actions between two hands, is one of the critical functions of the upper extremities for older adults contributing to successfully performing their fundamental movements of daily living [6, 7]. Older adults frequently revealed significant impairment in motor coordination between hands [6], and these deficits were correlated with the appearance of age-related cognitive diseases [5, 8].
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