title: Changes in distal muscle timing may contribute to slowness during sit to stand in Parkinsons disease.
abstract: OBJECTIVE
  To compare patterns of muscle activation in the lower extremity and subsequent forces during sit to stand in persons with Parkinsonism.
  
  
  BACKGROUND
  There is an interruption of the tibialis anterior/soleus interaction during forward oriented movements in some subjects with Parkinsonism, including sit to stand. This task is a major determinant of independence and 44% of those with Parkinsonism report difficulty.
  
  
  METHODS
  41 subjects with Parkinsonism were asked to stand up from a bench. Peak acceleration and vertical ground reaction forces, the slopes to these peaks, and the timing of events were measured. Surface electrodes were placed on tibialis anterior and soleus.
  
  
  RESULTS
  The slower group produced force at slower rate than the fast group. The slower group spent 64% of the time taken to stand to complete the flexion-momentum phase, and the fast group spent 56%. The slower group had a larger proportion of co-contraction trials than the other groups.
  
  
  CONCLUSIONS
  Slower subjects took longer to perform the task due to a longer time for seat off. Deficits recruiting tibialis anterior may contribute to the decreased rate of production of the acceleration forces and the longer time required for seat off. Relevance Decreased rate of rise of force is used to identify fallers in the elderly and subjects with stroke. Decreased rates of force production may therefore assist in identifying those with Parkinsonism at risk of falls. Treatment strategies designed to facilitate tibialis anterior activation may improve the functional performance of this task.
authors.affiliation: Department of Physical Therapy, University of Florida, P.O. Box 100154, Gainesville, FL 32610-0154, USA. mishop@phhp.ufl.edu
authors.forename: Mark
authors.initials: M
authors.lastname: Bishop
authors.forename: Denis
authors.initials: D
authors.lastname: Brunt
authors.forename: Neeti
authors.initials: N
authors.lastname: Pathare
authors.forename: Mansoo
authors.initials: M
authors.lastname: Ko
authors.forename: Jill
authors.initials: J
authors.lastname: Marjama-Lyons
mesh_terms: D000222:Adaptation, Physiological; D000368:Aged; D000369:Aged, 80 and over; D000843:Ankle Joint / Q000503:physiopathology*; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010300:Parkinson Disease / Q000145:classification / Q000503:physiopathology*; D004856:Postural Balance; D011187:Posture; D011597:Psychomotor Performance; D012720:Severity of Illness Index; D013314:Stress, Mechanical; D016474:Weight-Bearing