Dynamic sitting

Abstract

Individuals who cannot functionally reposition themselves adopt a passive body posture and suffer from physical discomfort in long-term sitting. To regulate body load and to prevent sitting related mobility problems, proper postural control is important. The inability to reposition underlines the importance for seating interventions that control body posture from automatic chair adjustments. We developed an adjustable simulator chair that allows the alignment of the trunk, pelvis and thighs to be controlled independently. This study describes the system for decoupled body segments adjustment and develops a predictive model that computes angular chair configuration for desired body postures. Eighteen healthy male subjects participated in this study. The experiment involved a protocol of five trials, each investigating the effect of individual chair segment angle adjustment on body segments rotation. Quasi-static chair adjustments were performed, in which angular chair configuration and body segments orientation were measured using an infrared motion capturing system and an inertial sensor attached on the pelvis. Linear best-fit equations together with the coefficients of determination were computed. Significant relations have been found between angular chair configuration and body segments orientation leading to an algorithm that predicts chair configuration for desired body posture. The predictive algorithm seems applicable to compute angular chair configuration for desired body posture when the initial body-chair configuration in known. For clinical application, future experiments must be performed on impaired individuals to validate the algorithm in terms of accuracy.

The impact of tilting on blood flow and localized tissue loading

“…However, given his lack of previous pressure ulcers, it calls into question whether the lack of response puts him at additional risk. Subject 4 is more consistent with the able-bodied non-responders seen in the study by van Geffen [11], as her blood flow was significantly higher than other participants in the upright seated position. Previous research has suggested that additional individual factors should be addressed when studying blood flow.…”

“…This is not surprising, as previous literature has addressed the individual nature of blood flow response [15,22,23]. Bader first suggested the idea of a "non-responder" in his 1990 paper.…”

“…In response to Hypothesis 1, small tilts (15 ) resulted in a significant increase in blood flow (p ¼ 0.016, Table 3). The magnitude of the Table 2).…”

“…In able-bodied participants, 25 of tilt resulted in approximately 5 of pelvic rotation [14]. However, the same author found that manipulating pelvic posture did not influence subcutaneous blood flow or oxygenation in persons with SCI [15]. This suggests that the small postural changes that might be induced by tilt are unlikely to affect blood flow.…”