Hiroki Aoki^1,, Shinichi Demura², Shunsuke Yamaji³, Yoshinori Nagasawa⁴, Toshiro Sato⁵

Individuals have unique sway characteristics, and to clarify interindividual variations, we must determine time points at which age and gender differences emerge. Therefore, this study aimed to compare center of pressure (COP) sway variables by gender and age and to examine relationships between mean positions and other sway variables. The study included 1362 participants, including healthy males (604) and females (758) aged 20–60 years. COP sway was measured once for 1 min. As COP sway variables, the mean positions X and Y, the mean position vector R, the rectangular area, and the standard deviations X and Y were selected. R goes from the two-dimensional coordinate start point to the intersection of mean positions X and Y. Mean position X showed no large gender or age differences (partial η2 < 0.010). In males, mean position Y was larger in the 20s, 50s, and 60s. Age difference was mainly observed in females, with the 50s and 60s tending to be larger than the 30s and 40s. The R tended to be similar to mean position Y. The unit time trajectory length, rectangular area, and standard deviations (SD) X and Y were all larger in males; in females, the degree of difference tended to be larger except for the SD Y(effect size (ES): 0.42–0.86). In any variable as a whole, the age difference was not large (partial η2 < 0.048) but larger in the 60s than in the 20s and 30s (ES: 0.24–0.60). Correlation between mean positions X and Y was low, and both mean positions had low correlation with other sway variables. Correlation between the rectangle area and both standard deviations or between the rectangle area and the unit time trajectory length was high. The R had moderate correlation with mean position Y, but low correlation with mean position X. In conclusion, mean position X revealed no large gender or age differences. Mean positions Y and R were larger in males than in females, and age differences were found mainly in females. Mean position Y greatly affected R. Mean position X had a low relationship with mean positions Y and R, but the latter’s relationship was relatively high. Both mean position variables had weak relationships with other sway variables. Mean position Y had gender and age differences similar to those of other sway variables, but mean position X did not.

mean position, elderly, position vector