# Static Factors in Sitting Comfort: Seat Foam Properties, Temperature, and Contact Pressure
## 3 Experimental Campaign
### Experiment 2: The Influence of Seat-Passenger Interface Pressure and Temperature
#### 3.3.2 Influence of Seat and Cover Features  
To verify the influence of the seat and the cover on sitting comfort, the S1 subject performed experiments with the current and older AP seats. As aforementioned, these seats have foams with similar dimensions but different densities. Moreover, their covers are produced from different materials. This way, it will be possible to investigate the influence of foam mechanical properties on interface pressure and the impact of interface temperature promoted by the seat cover. Results regarding the interface pressure of current and older AP comfort seats are depicted in Table 11.  
Generally, the older seat presented a lower average and peak pressures (-4 mmHg), while the main peak pressure occurs at the same region as the current seats (R1). Therefore, based on the previously found correlation between discomfort and pressure distribution, it can be concluded that the older foams induce higher comfort levels. This result is also sustained by the lower hardness presented by the older foams [13; 15; 32]. Pressure profiles (Figure 11) highlighted the differences between both foams. The current foam (Figure 11a) induced multiple pressure peaks at the ischial tuberosities regions and a generally higher average pressure. Concerning the older foam (Figure 11b), a reduced number of localised \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Subject**} & \multicolumn{4}{c}{**Sitting Area**} & \multicolumn{4}{c}{**Sitting Profile Line**} \\ \cline{2-9}  & **Min. (\({}^{\circ}\)C)** & **Max. (\({}^{\circ}\)C)** & **Max-Min (\({}^{\circ}\)C)** & **Avg. (\({}^{\circ}\)C)** & **Min. (\({}^{\circ}\)C)** & **Max. (\({}^{\circ}\)C)** & **Max-Min (\({}^{\circ}\)C)** & **Avg. (\({}^{\circ}\)C)** \\ \hline S1 & 26.2 & 32.9 & 6.7 & 30.5 & 23.9 & 31.3 & 7.4 & 27.6 \\ \hline S2 & 25.1 & 31.7 & 6.7 & 29.6 & 21.8 & 31 & 9.2 & 28.1 \\ \hline S3 & 24.3 & 32.1 & 7.8 & 29.8 & 23.3 & 31.1 & 7.8 & 28.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Temperature records regarding the standard seat. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Seat Type**} & \multicolumn{4}{c}{\(P_{max}\) (mmHg)} & \multicolumn{4}{c}{\(P_{avg}\) (mmHg)} & \multirow{2}{*}{**Contact Area**} \\ \cline{2-2} \cline{4-9}  & **R1** & **R2** & **L1** & **L2** & **R1** & **R2** & **L1** & **L2** & **(cm\({}^{2}\))** \\ \hline Current & 37 & 26 & 29 & 20 & 29 & 20 & 23 & 15 & 1076 \\ \hline Older & 33 & 16 & 27 & 17 & 28 & 14 & 21 & 14 & 983 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Maximum and mean pressure and contact area regarding the current and older AP comfort seat for subject S1. pressure peaks around the ischial tuberosities are observed. Those are coupled with a globally distributed pressure, reducing the average pressure. As described in Table 12, similar pressure tendencies were obtained on the standard seats. Standard and comfort seats only differ in terms of dimensions, namely thickness. Comparing the similarity of results of those seat types, it can be concluded that thickness does not influence pressure distribution. These findings contradict [PERSON] and [PERSON] (1998) and [PERSON] et al. (2019), who stated that increasing foam thickness reduces interface pressures. Seat cover influence was assessed by the thermographic images. The evaluation methodology was the same as previously conducted, where a sitting area and a defined profile line were applied. Table 13 presents the thermal results of both seat covers. Table 13 shows that fabric cover seats have lower minimum, maximum, and average temperatures independently of the seat type. Similar results were found within the same