Quickness of trunk movements in a seated position, regardless of the direction, is more important to determine the mobility in the elderly than the range of the trunk movement

Although trunk function is known to be critical for maintaining balance during gait, a detailed evaluation regarding the relationship between trunk function and mobility has not been performed. We previously reported that the ability of quick lateral trunk movements in a seated position reflects mobility in elderly people. In this study, we further examined whether trunk movement in the anterior–posterior direction is also a determinant of mobility. In addition, the correlation between range of lateral trunk movement and mobility was also examined. One hundred and forty community-dwelling elderly participants (73.3 ± 6.2 years) were enrolled in this study. We performed various trunk movement tests in a seated position, such as the seated side tapping test (SST), the seated anterior–posterior tapping test (APT), and the lateral sitting functional reach test (sitting reach test). Maximum gait speed and the timed up and go test (TUG) were performed to determine mobility. Parameters of trunk movement were compared. SST and APT showed moderate significant correlations with both maximum gate speed and TUG, while the sitting reach test weakly correlated (SST r = −0.58, p < 0.01, APT r = −0.63, p < 0.01, sitting reach test r = 0.30, p < 0.01). Moreover, multiple regression analysis revealed that SST and APT were independent indicators of both maximum gate speed and TUG, while the sitting reach test was not. These findings indicate that quickness, regardless of the direction of the movement, is more important than range in determining mobility in the elderly.