title: Influence of gravity compensation on muscle activation patterns during different temporal phases of arm movements of stroke patients.
abstract: BACKGROUND
  Arm support to help compensate for the effects of gravity may improve functional use of the shoulder and elbow during therapy after stroke, but gravity compensation may alter motor control.
  
  
  OBJECTIVE
  To obtain quantitative information on how gravity compensation influences muscle activation patterns during functional, 3-dimensional reaching movements.
  
  
  METHODS
  Eight patients with mild hemiparesis performed 2 sets of repeated reach and retrieval movements, with and without unloading the arm, using a device that acted at the elbow and forearm to compensate for gravity. Electromyographic (EMG) patterns of 6 upper extremity muscles were compared during elbow and shoulder joint excursions with and without gravity compensation.
  
  
  RESULTS
  Movement performance was similar with and without gravity compensation. Smooth rectified EMG (SRE) values were decreased from 25% to 50% during movements with gravity compensation in 5 out of 6 muscles. The variation of SRE values across movement phases did not differ across conditions.
  
  
  CONCLUSIONS
  Gravity compensation did not affect general patterns of muscle activation in this sample of stroke patients, probably since they had adequate function to complete the task without arm support. Gravity compensation did facilitate active arm movement excursions without impairing motor control. Gravity compensation may be a valuable modality in conventional or robot-aided therapy to increase the intensity of training for mildly impaired patients.
authors.affiliation: Roessingh Research and Development, Enschede, the Netherlands. g.prange@rrd.nl
authors.forename: G B
authors.initials: GB
authors.lastname: Prange
authors.forename: M J A
authors.initials: MJ
authors.lastname: Jannink
authors.forename: A H A
authors.initials: AH
authors.lastname: Stienen
authors.forename: H
authors.initials: H
authors.lastname: van der Kooij
authors.forename: M J
authors.initials: MJ
authors.lastname: Ijzerman
authors.forename: H J
authors.initials: HJ
authors.lastname: Hermens
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000368:Aged; D001132:Arm / Q000294:innervation / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D004185:Disability Evaluation; D004576:Electromyography; D005260:Female; D006112:Gravitation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation; D009119:Muscle Contraction / Q000502:physiology; D018908:Muscle Weakness / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D009989:Orthotic Devices / Q000639:trends*; D010291:Paresis / Q000209:etiology / Q000503:physiopathology* / Q000534:rehabilitation; D026741:Physical Therapy Modalities; D016059:Range of Motion, Articular; D020127:Recovery of Function / Q000502:physiology; D012371:Robotics; D020521:Stroke / Q000150:complications / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D013647:Task Performance and Analysis; D016474:Weight-Bearing / Q000502:physiology