# Prediction of Lower Leg Swelling in Driving Posture
## 3 Result and Discussion
### Relationship Between BI and Thigh Pressure Distribution
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Data**} & **Independent** & \multicolumn{2}{c}{**Non-Standardized**} & \multirow{2}{*}{**Standardized Coefficient**} & **Variance** \\  & **Variables** & **Coefficient** & & **Confication** & **Inflation Factor** \\ \hline \multirow{6}{*}{Male} & Time (\(t\)) & 0.036 & 0.468 & 1.000 \\ \cline{2-5}  & Tilt pressure (\(p_{t}\)) & 0.002 & 0.552 & 1.130 \\ \cline{2-5}  & Height (\(h\)) & \(-8.373\) & \(-0.184\) & 1.203 \\ \cline{2-5}  & Fat percentage (\(f\)) & \(-0.027\) & \(-0.064\) & 1.320 \\ \cline{2-5}  & Constant & 111.415 & — & — \\ \hline \multirow{6}{*}{Female} & Time (\(t\)) & 0.027 & 0.439 & 1.000 \\ \cline{2-5}  & Tilt pressure (\(p_{t}\)) & 0.002 & 0.527 & 1.002 \\ \cline{2-5}  & Height (\(h\)) & \(-7.202\) & \(-0.204\) & 1.016 \\ \cline{2-5}  & Fat percentage (\(f\)) & 0.010 & 0.017 & 1.018 \\ \cline{2-5}  & Constant & 107.867 & — & — \\ \hline \multirow{6}{*}{All} & Time (\(t\)) & 0.031 & 0.439 & 1.000 \\ \cline{2-5}  & Tilt pressure (\(p_{t}\)) & 0.002 & 0.659 & 1.421 \\ \cline{1-1} \cline{2-5}  & Height (\(h\)) & \(-3.405\) & \(-0.184\) & 1.264 \\ \cline{1-1} \cline{2-5}  & Fat percentage (\(f\)) & 0.001 & 0.002 & 1.150 \\ \cline{1-1} \cline{2-5}  & Constant & 101.950 & — & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of multiple regression analysis. Table 2 shows similar tendencies for each variable among the males, the females, and all the participants. Therefore, lower leg swelling could be predicted by sitting time \(t\), pressure in the tilt portion \(P_{t}\), participants' height \(h\), and body fat percentage \(f\), regardless of sex. A detailed discussion of each variable is presented below. First, the greatest influence with a positive effect (standardized regression coefficient) on BI was the pressure in the tilt portion \(P_{t}\). This result is consistent with those presented in Figure 6 and the findings of a study by [PERSON] et al. (2014). The second highest influence with a positive effect on BI was sitting time \(t\). [PERSON] et al. clarified that lower leg swelling progresses with time in a prolonged sitting posture ([PERSON] et al., 2016). However, the participants' height \(h\) had a negative effect on BI. This might be because thigh length is correlated with height. Since the same automobile seat was assigned to all the participants in this experiment, those with shorter thighs tended to have more compression on the poplileal vein. [PERSON] et al. measured skin blood flow in the lower legs in a sitting posture and found that skin blood flow was higher when pressure on the poplileal vein running through the posterior knee was small ([PERSON], 2017). Skin blood flow in the lower legs negatively affects lower leg swelling ([PERSON], 2017). In this experiment, lower leg swelling progressed more in shorter participants with stronger pressure on the posterior knee. Therefore, a negative correlation between height and BI was noted. The standardized partial regression coefficients for body fat percentage \(f\) were quite small for both the male and female participants. In this experiment, fat percentage had little effect on BI. Generally, women tend to have a higher fat percentage and lower blood flow in their bodies than men. Therefore, women are more likely than men to have lower leg swelling. Figures 9 and 10 indicate that the male participants have more data in the area above the straight line, while female participants have more data below the linear line. Conversely, the measured BI values were lower and higher than the predicted BI values in the men and women, respectively. The female hormones estrogen and progesterone are factors related to the greater progression of lower leg swelling noted in women compared to men. Estrogen and progesterone increase extracellular fluid and contribute to the progression of lower  
Figure 11: Relationship between measured and predicted BI for all participants. leg swelling [38; 39].