Influence of trunk flexion on biomechanics of wheelchair propulsion.

. Propulsion styles that are characterized by high stresses may influence the susceptibility of manual wheelchair users (MWCU) to upper limb injury. An experimental, crosssectional study was designed to compare physiological and biomechanical characteristics of wheelchair propulsion in two groups of MWCU—a trunk flexion propulsion style group (FG) and a non-trunk flexion propulsion style group (NFG)—across fresh and fatigued states . Data on joint kinetics and kinematics, handrim kinetics, propulsion temporal characteristics, and electromyography were collected at the fresh and fatigued states, and oxygen uptake was collected continuously, to characterize wheelchair propulsion performance of 19 MWCU during a submaximal exercise test to exhaustion . The FG was characterized by a more flexed trunk position accompanied by greater shoulder flexion and elbow extension (p<0 .05), which was accentuated with fatigue when compared to the NFG. When fatigued, marked decreases (p<0 .05) in key propulsion muscle activity were observed in the FG, but not in the NFG . Temporally, the This material is based on work supported by the Department of Veterans Affairs, VA Rehabilitation Research and Development Service, Washington, DC 20420 Presented in part at the Third North American Congress on Biomechanics, Waterloo, Ontario, Canada, 1998. Current Address: Pamela J . Russell, PhD, Dept. of Movement Arts, Health Promotion, & Leisure Studies, Bridgewater State College, Bridgewater, MA. Address all correspondence and requests for reprints to : Mary M. Rodgers, PhD, PT; University of Maryland, School of Medicine, Department of Physical Therapy, 100 Penn St., Baltimore, MD 21201-1082 ; email : mrodgers@umaryland .edu . FG decreased contact time on the handrim by 1 percent of the propulsion cycle when fatigued, in contrast to the NFG who increased contact time by 7 percent (p<0 .05) . Results suggest that a trunk flexion style of wheelchair propulsion may lead to potentially debilitating upper limb injury, since these individuals appear to be compensating for peripheral muscle fatigue.