Effects of Ageing on Adaptation during Vibratory Stimulation of the Calf and Neck Muscles

Abstract

Background: The ability to adapt and habituate based on prior experiences is important for human movement control, fall prevention and for the ability to enhance performance during various human activities. However, little is known about the ability for the elderly to adapt to balance perturbations in the lateral direction. Objective: To determine whether adaptation, i.e., the ability to adjust postural control to handle balance perturbations better over time, differed in the elderly subjects compared with young subjects in the anteroposterior and lateral directions, and whether the site of the balance perturbation or the presence or absence of vision affected the response. Methods: Postural stability was measured as anteroposterior and lateral torque variance in a young group (n = 18 (9 female and 9 male), average age = 29.1 years) and an elderly group (n = 16 (5 female and 11 male), average age = 71.5 years) with eyes open and closed during balance perturbations from calf and neck vibrations. After a 30-s period of quiet stance, these vibrations were repeated over a period of 200 s, so the adaptive responses could be analyzed by splitting the data into 50-s periods. Results: The adaptive responses in the anteroposterior and lateral directions were different. Adaptation in the anteroposterior direction occurred to an almost equal extent in the elderly and young, whereas adaptation in the lateral direction was markedly larger in the elderly in all tests except for neck vibration with eyes closed. Age, vision and vibration site were all influential factors for recorded body movements, but no significant combined effects were found. Conclusion: Balance perturbation instigates an adaptive response in the elderly in both the anteroposterior and lateral directions. However, during perturbation, age and vision are both very influential factors for the stability, thus associating the previously documented age-related decline in visual functioning with a higher risk of falls in this age range.

Change of Body Movement Coordination during Cervical Proprioceptive Disturbances with Increased Age

“…Typically, a multi-segmented movement pattern is used when an increase in whole body rigidity is insufficient [26,27] . Furthermore, in a previous study, we found no significant difference in quiet standing balance stability between older and younger adults when the vibrators were strapped to the neck or calf muscles [28] , indicating that these movement patterns were strategic. We have previously observed an uncorrelated movement pattern when subjects feel unthreatened during quiet standing [22] , and this was similar to the movement pattern in the present study in younger adults when the vibrators were strapped to the neck.…”

“…Whereas calf vibration elicits movement initially in a posterior direction, neck vibration elicits movement initially in an anterior direction. Vibration-induced movement is larger with calf vibration than with neck vibration in younger and older adults [15] . Also, the neck and calf muscles have different roles in the maintenance of postural stability.…”

“…This difference is thought to be because cervical proprioceptive signals are processed jointly with vestibular input with the head taken as reference [30,33,34] , thereby allowing cervical muscle afferents to contribute to the regulation of body orientation [17] . We have previously found that calf vibration results in larger torque variance towards the surface compared with neck vibration in both the elderly and young [15] . This ultimately suggests that the different effects of neck vibration in the elderly compared with the young were not associated with a larger perturbation, but instead associated with age-related changes to the interpretation of cervical proprioceptive information when disturbed by vibration.…”

“…Hence, the present findings suggest that the regulation of body orientation in older adults is more difficult than in younger adults especially during cervical proprioceptive disturbances. Proprioceptive vibration at the calf or neck evoked large whole body movement in the young and the elderly [28] . As a result of the vibration, both the young and the elderly adopted a higher correlation between the shoulder and head.…”

Vestibular modulation of postural stability: An update

“…Because as there is increase in the age the integration between different body systems will decrease and this may contribute for balance difficulties. Balance difficulties were one of the major factors that decrease the quality of life in elderly people [2][3][4]. Physical activity was reported to increase the strength of the muscles and limit the fall and faints due to postural disturbances [5].…”