Technology and Health Care 15 (2007) 195–202 195 IOS Press Technical Note How do normals move during prolonged wheelchair-sitting? E. Linder-Ganz a , M. Scheinowitz a , Z. Yizhar b , S.S. Margulies c and A. Gefen a,∗ a Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel b Department of Physical Therapy, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel c Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA Received 20 July 2006 Revised /Accepted 25 October 2006 Abstract. The clinical practice for minimizing the risk of pressure sores (PS) is to relief pressures under bony prominences of immobilized patients by changing their postures frequently. The US Department of Health advises to relief sitting pressures at least every 1 hour, and every 15 minutes for individuals who are body-abled. Surprisingly, there is paucity of information in the literature concerning motion of healthy subjects during prolonged sitting, which can be compared with these recommendations. Considering that healthy individuals are able to sit for hours without suffering injuries, such information seems particularly important. Accordingly, our objective was to measure frequency of postural changes and extent of motion during postural changes among healthy subjects who sit in a wheelchair (N = 10), in order to provide information that is missing in the literature of PS biomechanics. Subjects were asked to sit comfortably for 90 minutes, during which their trunk’s frontal and sagittal motions and sitting pressures were measured. We found that normals change their posture every 9 ± 6 minutes in the sagittal plane, and independently, every 6 ± 2 minutes in the frontal plane. Shoulders, thoracic-spine and lumbar-spine frontal plane motions were 8 ± 4 ◦ , 14 ± 7 ◦ and 15 ± 7 ◦ , respectively, and sagittal trunk-thigh movement was 10.3 ± 7 ◦ . The frequency of postural changes in normals, measured herein, was higher than frequencies reported in the literature for patients who suffered PS. This small study population therefore supports the hypothesis that prolonged immobilization contributes to PS onset. Keywords: Decubitus ulcer prevention, immobilization, posture, pressure sores, rehabilitation 1. Introduction Pressure sores (PS) are a frequent and potentially fatal complication in permanent wheelchair users [3]. Between 25 and 80% of spinal cord injury (SCI) patients suffer PS [8,9,19] and 7–8% of death cases among these patients are due to PS complications such as sepsis [15]. The costs for treating PS associated with SCI are substantial, exceeding 1.2 billion dollars annually in the United States alone [1,19]. Most PS appear in the vicinity of bony prominences, and PS under the coccyx and ischial tuberosities are typical (30–36% of cases) for wheelchair-bound patients [21,22]. ∗ Address for correspondence: Dr. Amit Gefen, Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, TelAviv 69978, Israel. Tel.: +972 3 640 8093; Fax: +972 3 640 5845; E-mail: gefen@eng.tau.ac.il. 0928-7329/07/$17.00  2007 – IOS Press and the authors. All rights reserved