Author(s): OYAMA, Y., KAMEOKA, M., SAKAGUCHI, Y., NAKANO, T., MURAYAMA, T., Institution: TOIN UNIVERSITY OF YOKOHAMA, Country: JAPAN, Abstract-ID: 1721

INTRODUCTION:
To avoid falls, individuals must recognize disturbances and respond physically using strategies appropriate to the situation. A stepping strategy provides the final measure for avoiding falls, and a proper stepping movements can reduce fall risk in older adults. Such fall-avoidance movements require two essential abilities: agility, defined as a rapid response to disturbances, and balance, to ensure bodily stability following stepping. Many studies have focused on either agility or balance alone, separately examining their associations of these two abilities with falls. However, research that considers the two as forming part of a continuous sequence of movements and evaluates them integrally remains limited. We developed a reaction step test (RST) to integrate agility and balance, confirming its reliability and validity and examining its association with falls. The age-related changes in reaction time and postural stability assessed by this test have not been sufficiently investigated. This study examined age-related changes in reaction time and postural stability following stepping in the RST.
METHODS:
A total of 202 middle-aged and older adults (86 men, 116 women) performed the RST. Participants stood upright on a pressure-sensitive mat and were instructed to take a quick step forward onto a stabilometer following the onset of a visual stimulus. After they step forward, they were required to stand on both legs for 10 s. The time from stimulus onset to foot-off was evaluated as agility, whereas the poststep center of pressure sway while standing on both legs was evaluated as balance. The participants were categorized into four age groups: 40s–50s, 60s, 70s, and 80s–90s. Age-related changes in agility and balance were examined using the Jonckheere–Terpstra trend test. In addition, simple-regression analyses were conducted for each age group, with balance as the dependent variable and reaction time as the independent variable, to examine the relationship between agility and balance.
RESULTS:
Significant age-related declines were observed in both agility and balance. Agility showed a marked decline in participants in their 80s–90s, whereas balance declined consistently with age beginning in the 60s. When examining the relationship between agility and balance within each age group using simple-regression analysis, no significant correlation was found in participants in their 40s–50s. A positive correlation trend was observed in participants in their 60s, and a significant positive correlation was found in the 70s and 80s–90s.
CONCLUSION:
The relationship between reaction time and postural stability in the RST differed across age groups. While agility and balance functioned relatively independently in middle-aged adults, delayed reaction time in older adults was associated with reduced postural stability following stepping.