## 3 Results  
Table 1 and Figure 5 show the results of a split-plot design for the differences in COP-FB according to participant groups and visual conditions. Only the participant factor was significant, and the visual factor and interaction were not significant. Therefore, differences in COP-FB between participant groups were analyzed using Student's \(t\)-test. The difference between participant groups was observed in the eyes-open condition and was significantly smaller in the trampoline gymnasts than in the healthy men (\(p<0.05\)). There was no significant difference between the participant groups in the eyes-closed condition.  
Table 2 and Figure 6 show the results of a split-plot design for the difference in COP-LR according to participant groups and visual conditions. Neither the participant factor, visual factor, nor interaction were significant. The COP-LR tended to be lower in the trampoline gymnasts than in the healthy men under both eyes-open and eyes-closed conditions, but no significant differences were observed.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Source** & **df** & **SS** & **MS** & **F Value** & \(p\)**-Value** \\ \hline Participant group (A) & 1.802 & 1 & 1.802 & 2.503 & 0.046 * \\ Visual condition (B) & 0.001 & 1 & 0.001 & 0.001 & 0.978 \\ A \(\times\) B & 0.603 & 1 & 0.603 & 0.837 & 0.366 \\ Error & 25.923 & 36 & 0.720 & & \\ Total & 140.855 & 40 & & & \\ \hline \hline \end{tabular}  
* df: degree of freedom. SS: sum of squares. MS: mean square.
* \(p<0.05\): denotes statistically significant difference.  
\end{table}
Table 1: Results of a split-plot design for the difference in COP-FB according to participant group and visual condition.  
Figure 5: Comparison of forward–backward displacement of the center of foot pressure (COP-FB) under eyes-open and eyes-closed conditions. Measurements are expressed as means \(\pm\) SD. Error bar indicates standard error of the mean. Differences between participant groups were observed in COP-FB in the eyes-open condition and were significantly smaller in the trampoline gymnasts than in the healthy men (\(p<0.05\)). No significant differences were observed between visual conditions in either participant group.  
Figure 7 shows the results of the correlation analysis between COP-FB and H-FB. A strong positive correlation was observed between COP-FB and H-FB (R = 0.750, \(p\) < 0.05). There was a tendency for the amount and direction of displacement in the forward and backward direction of COP to coincide with the landing position.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Source** & **df** & **SS** & **MS** & **\(F\) Value** & **\(p\)-Value** \\ \hline Participant group (A) & 0.261 & 1 & 0.261 & 3.861 & 0.057 \\ Visual condition (B) & 0.107 & 1 & 0.107 & 1.586 & 0.216 \\ A \(\times\) B & 0.002 & 1 & 0.002 & 0.023 & 0.880 \\ Error & 2.432 & 36 & 0.068 & & \\ Total & 16.246 & 40 & & & \\ \hline \hline \end{tabular}  
\(\ddagger\): degree of freedom. SS: sum of squares. MS: mean square.  
\end{table}
Table 2: Results of a split-plot design for the difference in COP-LR according to participant group and visual condition.  
Figure 6: Comparison of left–right displacement of the center of foot pressure (COP-LR) under eyes-opened and eyes-closed conditions. Measurements are expressed as means \(\pm\) SD. Error bar indicates standard error of the mean. There were no significant differences in COP-LR between healthy men and trampoline gymnasts in the eyes-open and eyes-closed conditions. In addition, no significant differences were observed between visual conditions in either participant group.  
Figure 8 shows the results of the correlation analysis between COP-LR and H-LR. A strong positive correlation was observed between COP-LR and H-LR (R = 0.702, \(p\) < 0.05). There was a tendency for the amount and direction of displacement in the left-right direction of COP to coincide with the landing position.