title: Joint torques and dynamic joint stiffness in elderly and young men during stepping down.
abstract: OBJECTIVE
  To compare the joint torque pattern and dynamic joint stiffness at the knee and ankle in elderly and young men during stepping down.
  
  
  BACKGROUND
  Adequate joint stiffness is critical during the single support phase to control forward and downward body momentum.
  
  
  METHODS
  Six active elderly men (mean 67.7) and six young men (mean 23.6) of similar body mass and height, were filmed stepping down from one force platform to another. Repeated trials were undertaken at three different step heights (200, 250, and 300 mm).
  
  
  METHODS
  Joint torques were determined for the ankle and knee of the support limb throughout the single support phase. The gradient of the joint torque-angle graph was calculated to define dynamic joint stiffness of the ankle and knee in two phases; (I) from initiation of movement until heel-off of the supporting limb, and (II) from heel-off of the supporting limb to contra-limb touch down.
  
  
  RESULTS
  Maximum ankle torque values were lower in the elderly and occurred at a larger dorsiflexion angle (P<0.05). Knee torque patterns were similar in both groups. Phase I ankle stiffness was significantly less in the elderly (4.0-5.2 Nm/ degrees ) at all step heights compared to the young (7.6 - 8.7 Nm/ degrees ). In both groups ankle stiffness in Phase II increased with step height, while knee joint stiffness decreased.
  
  
  CONCLUSIONS
  The different torque pattern and lower dynamic ankle stiffness in the elderly, particularly for Phase I, suggested an altered control strategy. These findings highlight the importance of dynamic ankle joint stiffness in stepping down.
  
  
  CONCLUSIONS
  Understanding how the elderly step down may be important in developing strategies to prevent falls.
authors.affiliation: Active Life Span Research, Manchester Metropolitan University, Alsager ST7 2HL, UK. slark@glam.ac.uk
authors.forename: Sally D
authors.initials: SD
authors.lastname: Lark
authors.forename: John G
authors.initials: JG
authors.lastname: Buckley
authors.forename: Simon
authors.initials: S
authors.lastname: Bennett
authors.forename: David
authors.initials: D
authors.lastname: Jones
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Sargeant
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology*; D003198:Computer Simulation; D004548:Elasticity; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008124:Locomotion; D008297:Male; D008954:Models, Biological; D010808:Physical Examination / Q000379:methods; D013314:Stress, Mechanical; D019415:Torque; D016474:Weight-Bearing / Q000502:physiology*