title: Age-related changes in the initiation of gait: degradation of central mechanisms for momentum generation.
abstract: OBJECTIVE
  To investigate cross-sectionally age-related changes in the expression and biomechanical efficiency of the gait-initiation motor program.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Twenty healthy young research subjects and 20 healthy elderly subjects who volunteered from the community participated in this study at a university research laboratory.
  
  
  METHODS
  Participants performed gait-initiation trials at three speeds from a starting position on a force platform while ground reaction force data, 3-D motion analysis data, and electromyographic data were collected. Measures included: latency of tibialis anterior (TA) activation and soleus (SOL) and gastrocnemius (GA) inhibition, magnitude of center of pressure (COP) displacement, magnitude of momentum generated, and final walking velocity.
  
  
  RESULTS
  The expression of the central motor program governing gait initiation, as evidenced by the invariant timing between TA activation and SOL/GA inhibition, was seen in both the young and elderly populations, but the frequency was diminished in the latter group. The momentum-generating capacity of the COP shift mechanism was present but significantly diminished in the elderly population.
  
  
  CONCLUSIONS
  These findings suggest that the central nervous system uses stable, efficient mechanisms for dealing with the inherent instability of upright bipedalism and that the integrity of these mechanisms degrades with aging.
authors.affiliation: NeuroMuscular Research Center, Department of Biomedical Engineering, Boston University, MA 02215, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Polcyn
authors.forename: L A
authors.initials: LA
authors.lastname: Lipsitz
authors.forename: D C
authors.initials: DC
authors.lastname: Kerrigan
authors.forename: J J
authors.initials: JJ
authors.lastname: Collins
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D002490:Central Nervous System / Q000502:physiology*; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009040:Motion Pictures; D009048:Motor Skills / Q000502:physiology*; D012044:Regression Analysis