Settling down time following initial sitting and its relationship with comfort and discomfort.

This study examined the subjective rating of wheelchair comfort and discomfort (numerical rating scale questionnaire) and the duration of objective in-chair movement reduction "settling down time" following initial contact with the seating surface. Healthy young subjects (n = 22) sat for 5 min on contoured foam or wood cushion surfaces fitted to otherwise identical wheelchairs. Force sensing resistors attached to each quadrant of the sitting interface measured the relative movements of the subjects over time. A significant correlation was found between settling down time (SDT) and reported leg/feet discomfort (p = 0.003; correlation co-efficient = 0.44); and a significant negative correlation was found between SDT and overall comfort (p = 0.015; correlation co-efficient = -0.36). When comparing cushion surfaces: SDT was significantly longer (p < 0.0001) for subjects sitting on wood (5.8 s) compared to contoured foam (3.9 s); Leg/feet discomfort was significant higher (p = 0.007) for subjects sitting on wood (1.1 out of 10) compared to contoured foam (0.3 out of 10); Overall discomfort was significant higher (p = 0.009) for subjects sitting on wood (1.3 out of 10) compared to contoured foam (0.5 out of 10); Comfort was significantly lower (p = 0.001) for subjects sitting on wood (6.5 out of 10) compared to contoured foam (8.3 out of 10); Support was significantly lower (p = 0.001) for subjects sitting on wood (6.4 out of 10) compared to contoured foam (8 out of 10). The results of this study suggest that the shape and firmness of the surface at the buttock-wheelchair interface can affect a subject's SDT following initial contact with the seat as well as their perception of comfort and discomfort. In addition, there appears to be a relationship between longer SDT's and increased discomfort ratings, and shorter SDT's and increased comfort ratings. Therefore, testing for SDT's may be useful in the indirect objective assessment of wheelchair cushions and possibly other types of seating surfaces with design differences that aim to improve comfort and minimize discomfort.