Effects of long-duration sitting with limited space on discomfort, body flexibility, and surface pressure

- A method of determining the optimum seat pitch is proposed.
- A tight seat pitch does not seem to exacerbate in change of the body flexibility.
- The seat pitch has an influence on the severity of discomfort.
- The seat pitch has an influence on the average pressure on the seatpan.

The objective of this work is to analyze the effect of long-duration sitting on a seat with the limited space on discomfort, body flexibility and surface pressure, and the changes of discomfort, surface pressure and body flexibility with the sitting time. The experiment was that eighteen healthy subjects seated for long-duration (3 h) in three different seat pitches (32 inches, 30 inches and 28 inches) conditions in the laboratory. The discomfort, pressure, and body flexibility parameters have been measured during the experiments. Comparing the data between three seat conditions during the sitting time, the results show that there is a significant difference in the overall discomfort ratings and pressure variances between three different seat conditions after 3 h, and significant effects were found among the three different seat pitches for the discomfort rating of shoulder, middle back and low back after 3 h. No significant findings were seen in lumbar and hamstring flexibility. The relationship between subjective ratings and objective measurements has been analyzed with spearman analysis. The correlation analysis suggest that differences in arm and middle back discomfort were significantly negatively correlated to Sit-Reach(3) scores (Correlation Coefficients: 0.492 and −0.527; p values of 0.038 and 0.025, respectively). Differences in overall discomfort, thigh and knee were significantly correlated to average pressure (Correlation Coefficients: 0.562, 0.833 and 0.520; p values of 0.004, 0.001.and 0.027, respectively).Relevance to industry Nowadays many forms of public transport, especially prolonged flight, involve sitting in the seat with a confined sitting space for long time, which may have bad effects on the user's flexibility and discomfort perception. The survey of passenger's subjective perception for different seat pitches and their physiological changes is helpful to find a relationship between subjective perception and objective measurement and understand how seat pitch to influence the discomfort, and the result can provide a reference for determining the appropriate distance of seat pitch.