POSTURAL STEADINESS AFTER PROLONGED STANDING ON DIFFERENT SLOPED SURFACE IN YOUNG HEALTHY ADULTS

Abstract

Prolonged standing is related to various health problems such as lower back pain and lower extremity discomfort. This study was to investigate the effects of prolonged standing on posture control and whether the sloped surface is beneficial to adults who are required to stand for a long period of time. Twenty young healthy adults (age: [Formula: see text] years, height: [Formula: see text] cm, weight: [Formula: see text] kg, 6 males and 14 females) participated in this study. They were asked to perform a sixty-second quiet-standing evaluation first (i.e. the pre-test condition), then the thirty-minute standing test, and followed by the sixty-second standing test again (i.e. the post-test condition). They stood barefoot quietly on a force plate watching a video on television located 2 m ahead. Three sloped conditions, i.e. the level ground, inclined (with the ankle dorsiflexed), and declined (with the ankle plantarflexed), were randomly examined on separate days. The trajectory, maximal anteroposterior/mediolateral displacement, sway area, and complexity index (CI) of the center of pressure (CoP) during the standing tests were analyzed. Ten-point visual analogue scale (VAS) for perceived fatigue was also recorded. One-way ANOVA and paired t-test were used to analyze postural changes among sloped conditions before and after the prolonged standing. Signs of fatigue (VAS were [Formula: see text], [Formula: see text] and [Formula: see text] for the level, inclined, and declined conditions, respectively) and significant increases in all CoP measures for the three slope conditions after thirty minutes of standing (all [Formula: see text]) were noted. Trajectory was greatest under inclined, followed by the declined and level conditions ([Formula: see text]). The CI was generally greater under the declined surface than the level and inclined surfaces along with the thirty-minute standing. These findings indicated that prolonged standing resulted in fatigue and increased postural changes, particularly on the inclined surface. A greater complexity on the declined surface implied that participants had better adaptability while standing on a declined surface than a flat or inclined surface. Current findings suggested that a declined surface could be a suitable choice for a prolonged standing and further studies are warranted to evaluate its efficacy on different career workers.