Investigating whether differences in disposition for movement-specific reinvestment affect perception and postural control by older adults

Abstract

Some older adults have a high or low inclination to consciously attend to and control their movements through a process known as “reinvestment” (Masters, 1992). It is possible that older adults who have a high inclination for movement-specific reinvestment (high reinvestors) are more aware of their age-related physical limitations and declining physiological potential when performing postural-related movements. Therefore, when planning movement execution, they might perceive their physical abilities and the environment in ways that would conserve energy and reduce the risk of falls. Inclination for movement-specific reinvestment can be assessed using the Movement Specific Reinvestment Scale (MSRS) questionnaire. However, to quantify the extent to which conscious processing of movement occurs in real-time, electroencephalographic (EEG) measures could be taken during postural movements. This thesis is aimed to examine how the inclination for movement-specific reinvestment might alter the way older adults perceive their own physical abilities and the environment they interact with and to extend the current literature on the use of EEG as real-time measures of conscious processing of postural control. Four studies are presented in this thesis. Study 1, suggested that movement-specific reinvestment did not contribute to older adults’ perception of their distance to a curb or their step length. Since estimations in Study 1 were made retrospectively and there were no opportunities for actions to be carried out, Study 2 examined older adults’ estimations of the height of an obstacle that they would step over. Psychological stress from instability was introduced using a pair of unstable shoes. Although shoe stability was altered, movement-specific reinvestment did not seem to play a role in the way older adults perceived and stepped over the obstacle. Since MSRS cannot capture real-time conscious processing during movement execution, Study 3 utilized EEG measures to determine potential differences in conscious processing by those with different inclination for movement-specific reinvestment. It was found that those who scored lower on the MSRS (low reinvestors) were more likely to display changes in conscious processing when their stability was challenged. Finally, Study 4 explored whether a threat to stability could trigger high reinvestors to consciously process their postural balance. However, it was found that a threat to stability via a collapsible surface affected the low and not the high reinvestors. In conclusion, it appears that movement-specific reinvestment might not have a role in self-perceived physical ability, egocentric distance, and obstacle height estimations. Stability changes achieved through shoe manipulation does not seem to heighten movement-specific reinvestment to the extent that it would alter the way obstacles are crossed. Similarly, change in stability achieved through decreasing the base of support and increasing postural threat does not seem to trigger high reinvestors to engage in greater conscious processing. The findings extends knowledge about the role that movement-specific reinvestment has in older adults’ perception and conscious processing when maintaining postural stability. However, further studies are needed to determine whether there are thresholds that when breached, could trigger movement-specific reinvestment to take place.