title: Movement accuracy changes muscle-activation strategies in female subjects during a novel single-leg weight-bearing task.
abstract: OBJECTIVE
  Understanding of how female subjects learn to move accurately during a resisted weight-bearing task is limited. The purpose of this study was to examine the muscle activation patterns used by female subjects in learning a novel single-leg squat (SLS) task under visual and nonvisual conditions.
  
  
  METHODS
  Prospective training study.
  
  
  METHODS
  University research setting.
  
  
  METHODS
  Ten healthy young female participants.
  
  
  METHODS
  Subjects tracked a sinusoidal target (knee displacement) during a resisted SLS exercise during the course of 4 days, under eyes open (EO) and eyes closed (EC) conditions with the use of a custom-designed weight-bearing exercise device.
  
  
  METHODS
  The accuracy of performance in tracking the target and electromyographic activity (EMG) of 5 muscles around the knee were monitored.
  
  
  RESULTS
  Subjects improved their accuracy of performance by day 2 (40% decrease in error) and retained the accuracy on day 4. Error during the EC condition was 3 times greater than EO condition. Quadriceps-to-hamstrings coactivation ratio increased with the improved accuracy from the learning. Absence of visual feedback was accompanied by a decrease in the quadriceps-to-hamstrings coactivation ratio for this task.
  
  
  CONCLUSIONS
  The muscle synergistic activity around the knee changes as the accuracy of the task improves during a resisted weight-bearing task. This activation pattern represents a feed forward control plan that the central nervous system adopted to optimize accurate weight-bearing knee displacement. Rehabilitation specialists should consider manipulating the visual feedback and accuracy of performance when developing weight-bearing rehabilitation training protocols to improve neuromuscular control in female patients.
authors.affiliation: Neural Plasticity Lab/Rehab Institute of Chicago, Chicago, IL, USA.
authors.forename: Sangeetha
authors.initials: S
authors.lastname: Madhavan
authors.forename: Richard K
authors.initials: RK
authors.lastname: Shields
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D011446:Prospective Studies; D055070:Resistance Training; D013647:Task Performance and Analysis; D016474:Weight-Bearing / Q000502:physiology; D055815:Young Adult