Validation of a new index for seat comfort assessment based on objective and subjective measurements

Purpose: This work aims at validating a new statistical index (Weighted Pressure Comfort Loss, WPCL) for seat comfort assessment. The validation is carried out by deepening the relationship between subjective comfort evaluations and objective measures of seat comfort and comparing, from an engineering standpoint, the new index with the pressure peak which is currently one of the most used indexes for seat comfort assessment. Method: In the experimental phase, 22 experimenters evaluated four office chairs, by using different evaluation scales and methods (rating, ranking, comfort degree). The subjective comfort perceptions were collected through questionnaires. At the same time, several objective parameters related to seat comfort were measured by using a capacitive mat. In order to select the objective comfort measures which are significantly associated to the perceived comfort, a logistic regression model was adopted. Result: The logistic regression model selected the peak pressure as a significant predictor of perceived comfort whereas, the hypothesis of absence of correlation between the perceived comfort and the WPCL index cannot be rejected. However, from an engineering standpoint, the final seat rating evidences substantial coherence of peak pressure and WPCL index, showing not redundant results useful to design team for seat comfort improvement. Since results were strongly influenced by experimental conditions and anthropometric variability of the experimenters, further investigations should be carried out. On the basis of the first experiments, a refinement of the index and new test conditions could be investigated.