Dynamic sitting

Many wheelchair-users with reduced postural stability adopt a static body posture and have problems with the performance of functional movement tasks. Prolonged static sitting with a flexed spinal posture and posterior tilted pelvis unconditionally leads to all kinds of physical discomfort including the development of pressure ulcers and low back injury. Most of these problems occur from sustained mechanical tissue loading. Dynamic seating interventions are therefore needed to alleviate the load bearing tissue periodically. We developed an experimental simulator chair en evaluated several seating interventions that are designed to enhance functional movement and to prevent physical discomfort due to prolonged static sitting. Theoretical and experimental evaluations were performed in ablebodied subjects and in subjects with a spinal cord injury (SCI). The following research questions have been answered.

How can sitting be controlled?

Based on a parallelogram design that aligns the chair pivots with the anatomical axes for body segments rotation, we developed a technique that adjusts all three body segments (trunk, pelvis, thighs) separately. Together with simultaneous measurement of body segments orientation, so-called body segments decoupling seemed applicable to control sitting posture when individuals lack the strength to do this themselves.

What interventions are effective to regulate body load associated with physical discomfort (i.e. pressure ulcers and low back pain)?

A combination of seat inclination, saggital decoupled pelvis rotation and a dynamic tuberal support appeared beneficial to regulate the load bearing tissue of the ischial buttock region and lower back simultaneously.

What interventions benefit the performance of functional movement in impaired sitting?

It has been suggested in literature that seating interventions which adjust pelvis angle in sagittal direction might influence spinal posture and the performance of functional movement. We investigated this in ten male SCI-individuals and found that decoupled pelvis alignment affects balance control in impaired sitting and that anterior tilted pelvis postures potentially benefit the functional performance in daily wheelchair-use.