title: Early motor learning changes in upper-limb dynamics and shoulder complex loading during handrim wheelchair propulsion.
abstract: BACKGROUND
  To propel in an energy-efficient manner, handrim wheelchair users must learn to control the bimanually applied forces onto the rims, preserving both speed and direction of locomotion. Previous studies have found an increase in mechanical efficiency due to motor learning associated with changes in propulsion technique, but it is unclear in what way the propulsion technique impacts the load on the shoulder complex. The purpose of this study was to evaluate mechanical efficiency, propulsion technique and load on the shoulder complex during the initial stage of motor learning.
  
  
  METHODS
  15 naive able-bodied participants received 12-minutes uninstructed wheelchair practice on a motor driven treadmill, consisting of three 4-minute blocks separated by two minutes rest. Practice was performed at a fixed belt speed (v = 1.1 m/s) and constant low-intensity power output (0.2 W/kg). Energy consumption, kinematics and kinetics of propulsion technique were continuously measured. The Delft Shoulder Model was used to calculate net joint moments, muscle activity and glenohumeral reaction force.
  
  
  RESULTS
  With practice mechanical efficiency increased and propulsion technique changed, reflected by a reduced push frequency and increased work per push, performed over a larger contact angle, with more tangentially applied force and reduced power losses before and after each push. Contrary to our expectations, the above mentioned propulsion technique changes were found together with an increased load on the shoulder complex reflected by higher net moments, a higher total muscle power and higher peak and mean glenohumeral reaction forces.
  
  
  CONCLUSIONS
  It appears that the early stages of motor learning in handrim wheelchair propulsion are indeed associated with improved technique and efficiency due to optimization of the kinematics and dynamics of the upper extremity. This process goes at the cost of an increased muscular effort and mechanical loading of the shoulder complex. This seems to be associated with an unchanged stable function of the trunk and could be due to the early learning phase where participants still have to learn to effectively use the full movement amplitude available within the wheelchair-user combination. Apparently whole body energy efficiency has priority over mechanical loading in the early stages of learning to propel a handrim wheelchair.
authors.affiliation: University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, The Netherlands. r.j.k.vegter@umcg.nl.
authors.forename: Riemer J K
authors.initials: RJ
authors.lastname: Vegter
authors.affiliation: University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, The Netherlands. j.hartog@umcg.nl.
authors.forename: Johanneke
authors.initials: J
authors.lastname: Hartog
authors.affiliation: University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, The Netherlands. s.d.groot@reade.nl.|Amsterdam Rehabilitation Research Center Reade, Amsterdam, The Netherlands. s.d.groot@reade.nl.
authors.forename: Sonja
authors.initials: S
authors.lastname: de Groot
authors.affiliation: University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, The Netherlands. c.j.c.lamoth@umcg.nl.
authors.forename: Claudine J
authors.initials: CJ
authors.lastname: Lamoth
authors.affiliation: University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, The Netherlands. michel.bekker@paraplegie.ch.|Swiss Paraplegic Research, Nottwil, Switzerland. michel.bekker@paraplegie.ch.
authors.forename: Michel J
authors.initials: MJ
authors.lastname: Bekker
authors.affiliation: University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, The Netherlands. j.w.van.der.scheer@umcg.nl.
authors.forename: Jan W
authors.initials: JW
authors.lastname: van der Scheer
authors.affiliation: University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, The Netherlands. l.h.v.van.der.woude@umcg.nl.|University of Groningen, University Medical Center Groningen, Center for Rehabilitation, Groningen, The Netherlands. l.h.v.van.der.woude@umcg.nl.
authors.forename: Lucas H V
authors.initials: LH
authors.lastname: van der Woude
authors.affiliation: Faculty of Human Movement Sciences, Research Institute MOVE, Vrije Universiteit, Amsterdam, The Netherlands. h.e.j.veeger@vu.nl.|Faculty of Mechanical, Maritime and Materials Engineering, Section Biomechatronics & Biorobotics, Delft University of Technology, Delft, The Netherlands. h.e.j.veeger@vu.nl.
authors.forename: Dirkjan H E J
authors.initials: DH
authors.lastname: Veeger
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006801:Humans; D006811:Humerus / Q000502:physiology; D007206:Individuality; D007858:Learning / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D011214:Practice, Psychological; D012782:Shoulder / Q000502:physiology*; D034941:Upper Extremity / Q000502:physiology*; D014910:Wheelchairs; D055815:Young Adult