Differences between Young and Older Adults in the Control of Weight Shifting within the Surface of Support (original) (raw)
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Postural control of elderly: Moving to predictable and unpredictable targets
2012
Impaired postural control with muscle weakness is an important predictor of falls within the elderly population. Particular daily activities that require weight shifting in order to be able to reach a specific target (a cup on a table) require continuous adjustments to keep the body's center of mass balanced. In the present study postural control was examined in healthy elderly and young subjects during a task in which subjects had to move the body's center of mass towards a virtual target on a screen that appeared at predictable and unpredictable locations. Postural control decreased with unpredictable targets, e.g. movement time was larger, trajectories more irregular. The results indicate that even though older individuals clearly benefitted from the early release of target location information, young individuals improved even more when target information became available. This indicates that the young were better able to use this information prospectively for executing the target directed movement quickly and accurately.
Motriz: Revista de Educação Física
To investigate postural control between active (AOA) and inactive (IOA) older adults and active young adults (YA) due to the difficulty level of the postural task. Methods: 25 active YA, 31 AOA, and 30 IOA were invited to perform postural tasks with eyes open and closed: bipedal stance on a rigid surface, bipedal stance on an unstable surface, semi-tandem stance on a rigid surface, and semi-tandem stance on an unstable surface. Results: IOA (0.74 cm) presented higher COP displacement amplitude in the mediolateral direction than AOA (0.64 cm) only in bipedal stance on an unstable surface with eyes closed condition (p ≤ 0.0001). In relation to frequency variables, IOA (0.37 Hz) presented a greater frequency band with 50% of the spectral power in the mediolateral direction than AOA (0.28 Hz) in all experimental conditions, except for semi-tandem stance on a rigid surface (p ≤ .0001). AOA (0.62 cm | 0.28 Hz) and IOA (0.67 cm | 0.37 Hz) presented an increase in time/frequency variables in both directions (anteriorposterior and mediolateral) than YA (0.52 cm | 0.17 Hz) (p ≤ 0.0001) that indicates a worse performance of postural control as the level of task difficulty increased, such as unstable base with eyes open and closed. Conclusion: Older adults tend to present greater COP sway and velocity when subjected to complex tasks compared with younger, which is more evident in older adults physically inactive. This could be considered an adaptive strategy by older adults to minimize the risk of losing balance and, consequently, falling.
The Journal of Physiology, 2002
We investigated the effects of ageing on balance corrections induced by sudden stance perturbations in different directions. Effects were examined in biomechanical and electromyographic (EMG) recordings from a total of 36 healthy subjects divided equally into three age groups (20-34, 35-55 and 60-75 years old). Perturbations consisted of six combinations of support-surface roll (laterally) and pitch (forward-backward) each with 7.5 deg amplitude (2 pure pitch, and 4 roll and pitch) delivered randomly. To reduce stimulus predictability further and to investigate scaling effects, perturbations were at either 30 or 60 deg s _1. In the legs, trunk and arms we observed age-related changes in balance corrections. The changes that appeared in the lower leg responses included smaller stretch reflexes in soleus and larger reflexes in tibialis anterior of the elderly compared with the young. For all perturbation directions, onsets of balance correcting responses in these ankle muscles were delayed by 20-30 ms and initially had smaller amplitudes (between 120-220 ms) in the elderly. This reduced early activity was compensated by increased lower leg activity after 240 ms. These EMG changes were paralleled by comparable differences in ankle torque responses, which were initially (after 160 ms) smaller in the elderly, but subsequently greater (after 280 ms). Findings in the middle-aged group were generally intermediate between the young and the elderly groups. Comparable results were obtained for the two different stimulus velocities. Stimulus-induced trunk roll, but not trunk pitch, changed dramatically with increasing age. Young subjects responded with early large roll movements of the trunk in the opposite direction to platform roll. A similarly directed but reduced amplitude of trunk roll was observed in the middle-aged. The elderly had very little initial roll modulation and also had smaller stretch reflexes in paraspinals. Balance-correcting responses (over 120-220 ms) in gluteus medius and paraspinals were equally well tuned to roll in the elderly, as in the young, but were reduced in amplitude. Onset latencies were delayed with age in gluteus medius muscles. Following the onset of trunk and hip balance corrections, trunk roll was in the same direction as support-surface motion for all age groups and resulted in overall trunk roll towards the fall side in the elderly, but not in the young. Protective arm movements also changed with age. Initial arm roll movements were largest in the young, smaller in the middle aged, and smallest in the elderly. Initial arm roll movements were in the same direction as initial trunk motion in the young and middle aged. Thus initial roll arm movements in the elderly were directed oppositely to those in the young. Initial pitch motion of the arms was similar across age groups. Subsequent arm movements were related to the amplitude of deltoid muscle responses which commenced at 100 ms in the young and 20-30 ms later in the elderly. These deltoid muscle responses preceded additional arm roll motion which left the arms directed 'downhill' (in the direction of the fall) in the elderly, but 'uphill' (to counterbalance motion of the pelvis) in the young. We conclude that increased trunk roll stiffness is a key biomechanical change with age. This interferes with early compensatory trunk movements and leads to trunk displacements in the direction of the impending fall. The reversal of protective arm movements in the elderly may reflect an adaptive strategy to cushion the fall. The uniform delay and amplitude reduction of balance-correcting responses across many segments (legs, hips and arms) suggests a neurally based alteration in processing times and response modulation with age. Interestingly, the elderly compensated for these 'early abnormalities' with enlarged later responses in the legs, but no similar adaptation was noted in the arms and trunk. These changes with age provide an insight into possible mechanisms underlying falls in the elderly.
Age-related changes in postural control to the demands of a precision task
Human movement science, 2015
Optimal sensorimotor integration is needed to maintain the precision of a visuomotor postural task. Furthermore, cognitive resources have been suggested to be involved in maintaining balance, especially in older adults. This study investigated how older and younger adults differed in employing sensorimotor strategies in a dual-task situation. Older (age 65-84years) and younger adults (age 19-30years) performed a visually-based, postural tracking task in different body orientations (from 0° to 45°), which necessitated slightly different task goals. On some trials, participants performed a concurrent silent arithmetic task with the visuomotor tracking task. The results demonstrated that sensorimotor control declined with age. Older adults showed greater medial-lateral center of pressure variability compared to younger adults in the precision task. Younger adults displayed a trend to decrease anterior-posterior variability, but older adults exhibited an opposite trend when the body ori...
Postural Sway during Dual Tasks in Young and Elderly Adults
Gerontology, 2007
tions in sway during performance of the search task relative to sway during viewing of a blank target. The sway was also reduced for both groups during viewing a near target when compared to a distant target. Conclusions: The results suggest that, despite the overall increase in postural sway with aging, subtle integration of visual information by the postural control system is not affected by aging. The present results support the idea that dual tasks do not necessarily lead to an increase in postural sway. This effect, found here in elderly adults, raises questions about widely held views in which age-related changes in postural sway are related to competition between postural control and other activities for central processing resources.
Age and Ageing, 1998
Background and aims: the transfer from sitting to standing and back to sitting as the two phases of the same task has never been studied in elderly people. The purposes of this study were to analyse and compare kinematic features of the whole task (standing up and sitting down) and to determine whether there are age-related differences upon movement kinematics in healthy elderly persons during the whole sequence (standing up and sitting down). Methods: the movements of various parts of the body were measured with a 100 Hz television image analyser that computed the co-ordinates of small reflective markers glued onto the skin of the subjects. The task was conducted using an armless chair set to 100% of knee height under four conditions: at normal speed in light, at normal speed in the dark, at fast speed in light and at fast speed in the dark. Type of study: laboratory study. Results: in young subjects, the task was characterized by similar acromion trajectories and angular displacement of trunk in standing up and sitting down and by a stabilization of the head in space during the two phases. However, the time required to achieve the movement was found to be greater in sitting down than in standing up, and an adjustment of velocity appeared in final part of the movement before reaching the chair. In sitting down, as in carrying out a pointing task of upper limb, an adjustment was required to achieve accuracy. This feature was not found in standing up. Age-related differences appeared to be more important during sitting down than during standing up. Moreover, deterioration of head stability was found in elderly subjects, particularly when the task was achieved rapidly and in darkness. Conclusion: there is a relationship between changes in the motor control of the task, which appeared during periods of potential postural instability, and the effects of ageing on postural stability.
Age-Related Differences in Movement Control: Adjusting Submovement Structure To Optimize Performance
The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 1997
Noise-related explanations for movement slowing (e.g., suggest that with age, the noise-to-force ratio increases. This means that when an older adult produces a force, the noise associated with the resulting movement is greater than when a younger adult produces that same force. Given this assumption, older adults produce slower movements than younger adults. Given greater levels of motor noise, they move more slowly in order to maintain the same level of movement accuracy as younger adults.
Age related differences in movement control: adjusting sub-movement structure to optimize performanc
1997
Noise-related explanations for movement slowing (e.g., suggest that with age, the noise-to-force ratio increases. This means that when an older adult produces a force, the noise associated with the resulting movement is greater than when a younger adult produces that same force. Given this assumption, older adults produce slower movements than younger adults. Given greater levels of motor noise, they move more slowly in order to maintain the same level of movement accuracy as younger adults.
Older adults utilize less efficient postural control when performing pushing task
Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, 2015
The ability to maintain balance deteriorates with increasing age. The aim was to investigate the role of age in generation of anticipatory (APA) and compensatory (CPA) postural adjustments during pushing an object. Older (68.8±1.0years) and young adults (30.1±1.4years) participated in the experiment involving pushing an object (a pendulum attached to the ceiling) using both hands. Electrical activity of six leg and trunk muscles and displacements of the center of pressure (COP) were recorded and analyzed during the APA and CPA phases. The onset time, integrals of muscle activity, and COP displacements were determined. In addition, the indexes of co-activation and reciprocal activation of muscles for the shank, thigh, and trunk segments were calculated. Older adults, compared to young adults, showed less efficient postural control seen as delayed anticipatory muscle onset times and delayed COP displacements. Moreover, older adults used co-activation of muscles during the CPA phase wh...