title: Laserlight visual cueing device for freezing of gait in Parkinson's disease: a case study of the biomechanics involved.
abstract: BACKGROUND
  Freezing of gait (FOG) is a serious gait disorder affecting up to two-thirds of people with Parkinson's disease (PD). Cueing has been explored as a method of generating motor execution using visual transverse lines on the floor. However, the impact of a laser light visual cue remains unclear.
  
  
  OBJECTIVE
  To determine the biomechanical effect of a laser cane on FOG in a participant with PD compared to a healthy age- and gender-matched control.
  
  
  METHODS
  The participant with PD and healthy control were given a task of initiating gait from standing. Electromyography (EMG) data were collected from the tibialis anterior (TA) and the medial gastrocnemius (GS) muscles using an 8-channel system. A 10-camera system (Qualisys) recorded movement in 6 degrees of freedom and a calibrated anatomical system technique was used to construct a full body model. Center of mass (COM) and center of pressure (COP) were the main outcome measures.
  
  
  RESULTS
  The uncued condition showed that separation of COM and COP took longer and was of smaller magnitude than the cued condition. EMG activity revealed prolonged activation of GS, with little to no TA activity. The cued condition showed earlier COM and COP separation. There was reduced fluctuation in GS, with abnormal, early bursts of TA activity. Step length improved in the cued condition compared to the uncued condition.
  
  
  CONCLUSIONS
  Laserlight visual cueing improved step length beyond a non-cued condition for this patient indicating improved posture and muscle control.
authors.affiliation: a Faculty of Health and Medicine , Lancaster University , Lancaster , UK and.
authors.forename: C J
authors.initials: CJ
authors.lastname: Egerton
authors.affiliation: b Allied Health Research Unit, University of Central Lancashire , Preston , UK.
authors.forename: P
authors.initials: P
authors.lastname: McCandless
authors.affiliation: b Allied Health Research Unit, University of Central Lancashire , Preston , UK.
authors.forename: B
authors.initials: B
authors.lastname: Evans
authors.affiliation: b Allied Health Research Unit, University of Central Lancashire , Preston , UK.
authors.forename: J
authors.initials: J
authors.lastname: Janssen
authors.affiliation: b Allied Health Research Unit, University of Central Lancashire , Preston , UK.
authors.forename: J D
authors.initials: JD
authors.lastname: Richards
mesh_terms: D001696:Biomechanical Phenomena; D003463:Cues; D004576:Electromyography; D005684:Gait; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007834:Lasers; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D018482:Muscle, Skeletal / Q000294:innervation*; D010300:Parkinson Disease / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology / Q000628:therapy*; D010775:Photic Stimulation / Q000295:instrumentation*; D016896:Treatment Outcome; D014796:Visual Perception
keywords: EMG; Parkinson's disease; gait; kinematics; kinetics