title: Age-related changes in rate and magnitude of ankle torque development: implications for balance control.
abstract: BACKGROUND
  One of the key components of postural control is the motor system's ability to produce appropriate torques to counteract perturbations that may lead to a loss of balance. Evidence exists to show that there is an age-related decline in absolute strength and in the ability to rapidly produce torque. The relationship between age-related decreases in these voluntary torque production capabilities and the ability to rapidly produce torques in a reactive balance task has not been studied. Thus, the purpose of this study was to examine the magnitude and rate of torque production in younger and older adults under reactive balance conditions.
  
  
  METHODS
  Older (OA) and younger (YA) adults received forward and backward support surface translations of varying amplitudes and velocities. Maximum ankle muscle torque (maxMa) and rate of change of ankle muscle torque (Ma) following a perturbation were calculated.
  
  
  RESULTS
  Two balance responses emerged: a no-step and a step response. With increasing perturbation difficulty, YA and OA used different responses. The no-step and step responses were examined for age-group differences in the force characteristics. No significant age-group differences were found for maxMa or rate of change of Ma within either no-step or step responses.
  
  
  CONCLUSIONS
  The results of this study suggest that neither the magnitude nor rate of ankle muscle torque production, as produced during the initial balance response in this set of reactive balance control tasks, determines the different balance responses seen in younger versus older adults.
authors.affiliation: Department of Kinesiology and Health Education, University of Texas at Austin, 78712, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Hall
authors.forename: M H
authors.initials: MH
authors.lastname: Woollacott
authors.forename: J L
authors.initials: JL
authors.lastname: Jensen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000842:Ankle / Q000502:physiology*; D001696:Biomechanical Phenomena; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology; D019415:Torque