Proceedings of The Physiological Society
King's College London (2009) Proc Physiol Soc 14, C7
Changes in upper limb reaching synergies with human ageing
M. Mayston1, S. F. Farmer3, C. Hopkins2
1. Neuroscience, Physiology, Pharmacology, University College London, London, United Kingdom. 2. Physiotherapy, Royal Hospital for Neurodisability, London, United Kingdom. 3. Neurology, University College London, London, United Kingdom.
Not much is known about the effects of ageing on the important upper limb functions of manipulation and movement of objects. Furthermore, it is important to understand the effects of normal ageing on upper limb movement synergies in order to improve the understanding of the pathophysiology and management of neurological conditions e.g. stroke. The aim of this study was to investigate the effects of hand-dominance and age on upper limb reaching functions. With ethical approval we studied 16 participants (age range 22-82 years, 55.1 ± 20.4: mean + SD: 4 male, 2 left-handed). Participants were excluded if they had previous neurological and/or musculoskeletal problems. Participants performed a reaching task involving movement of the shoulder, elbow and wrist in 3-D space. These movements were measured using the Cartesian Optoelectronic Dynamic Anthropometer (CODA;Charnwood Dynamics, UK) motion analysis system. Participants picked up and moved a cup across a table, released it, and then brought their arm back to the starting position. The task was carried out five times and data from all the trials were used in the analyses. Both left and right upper limbs were tested. Quaternion angles (angular motion) were calculated from the kinematic data using Matlab (Mathworks Inc, USA) routines developed for this study. Hand dominance did not significantly affect this task (Paired t-test: P>0.05), therefore data from left and right sides were pooled prior to age comparison. For the purposes of comparison subjects were divided into younger and older age groups (age 22-54 years, n=9 vs 64-82 years, n=7). Significant changes in angular motion were found with increasing age. There were increases in angular motion of the wrist at object pick up (Unpaired t-test: P < 0.05) and a significant decrease in total elbow movement (Unpaired t-test: P < 0.05). These data are displayed in Figure 1. Linear regression between angular motion at shoulder, elbow and wrist and age showed that wrist angular motion at object pick up, but not object release increased (F(1,158)=5.2) whilst shoulder and elbow angular motion decreased (F(1,158)=7.7; F(1,158)=17.8; ANOVA; P < 0.05 for shoulder, elbow and wrist pick-up).These results suggest that there are changes in movement synergies with ageing. The total angular movement at the shoulder and elbow decreases whilst total angular movement at the wrist increases. We do know yet whether the increase in wrist movement is compensatory for the decreases in shoulder and elbow movement.
Where applicable, experiments conform with Society ethical requirements