title: Modifications in Wheelchair Propulsion Technique with Speed.
abstract: OBJECTIVE
  Repetitive loading of the upper limb joints during manual wheelchair (WC) propulsion (WCP) has been identified as a factor that contributes to shoulder pain, leading to loss of independence and decreased quality of life. The purpose of this study was to determine how individual manual WC users with paraplegia modify propulsion mechanics to accommodate expected increases in reaction forces (RFs) generated at the pushrim with self-selected increases in WCP speed.
  
  
  METHODS
  Upper extremity kinematics and pushrim RFs were measured for 40 experienced manual WC users with paraplegia while propelling on a stationary ergometer at self-selected free and fast propulsion speeds. Upper extremity kinematics and kinetics were compared within subject between propulsion speeds. Between group and within-subject differences were determined (α = 0.05).
  
  
  RESULTS
  Increased propulsion speed was accompanied by increases in RF magnitude (22 of 40, >10 N) and shoulder net joint moment (NJM, 15 of 40, >10 Nm) and decreases in pushrim contact duration. Within-subject comparison indicated that 27% of participants modified their WCP mechanics with increases in speed by regulating RF orientation relative to the upper extremity segments.
  
  
  CONCLUSIONS
  Reorientation of the RF relative to the upper extremity segments can be used as an effective strategy for mitigating rotational demands (NJM) imposed on the shoulder at increased propulsion speeds. Identification of propulsion strategies that individuals can use to effectively accommodate for increases in RFs is an important step toward preserving musculoskeletal health of the shoulder and improving health-related quality of life.
authors.affiliation: Department of Biomedical Engineering, University of Southern California , Los Angeles, CA , USA.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Russell
authors.affiliation: Department of Biomedical Engineering, University of Southern California , Los Angeles, CA , USA.
authors.forename: Shashank
authors.initials: S
authors.lastname: Raina
authors.affiliation: Pathokinesiology Laboratory, Rancho Los Amigos National Rehabilitation Center , Downey, CA , USA.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Requejo
authors.affiliation: Department of Psychology, University of Southern California , Los Angeles, CA , USA.
authors.forename: Rand R
authors.initials: RR
authors.lastname: Wilcox
authors.affiliation: Pathokinesiology Laboratory, Rancho Los Amigos National Rehabilitation Center , Downey, CA , USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Mulroy
authors.affiliation: Department of Biomedical Engineering, University of Southern California , Los Angeles, CA , USA ; Department of Biological Sciences, University of Southern California , Los Angeles, CA , USA.
authors.forename: Jill L
authors.initials: JL
authors.lastname: McNitt-Gray
keywords: biomechanics; joint kinetics; propulsion; rehabilitation; shoulder pain; spinal cord injury; upper extremity; wheelchair