title: Lower extremity muscle activation during functional exercises in patients with and without chronic ankle instability.
abstract: OBJECTIVE
  To determine whether individuals with chronic ankle instability (CAI) exhibit altered neuromuscular control as demonstrated by surface electromyography (EMG) amplitudes compared with healthy controls during single-limb eyes-closed balance, Star Excursion Balance Test, forward lunge, and lateral hop exercises.
  
  
  METHODS
  A cross-sectional laboratory study.
  
  
  METHODS
  A research laboratory.
  
  
  METHODS
  Fifteen young adults with CAI and 15 healthy controls.
  
  
  METHODS
  The subjects performed functional exercises while surface EMG signals were recorded from the tibialis anterior, peroneus longus, lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius.
  
  
  METHODS
  Surface EMG amplitudes (root mean square area) for each muscle, muscles of the shank (distal 3 muscles), muscles of the thigh (proximal 3 muscles), and total muscle activity (all 6 muscles) of the lower extremity were analyzed and compared between the groups.
  
  
  RESULTS
  Individuals with CAI demonstrated significantly less EMG activity in the muscles of the lower extremity during all 4 functional exercises. Effect sizes for significant differences between groups ranged from -0.75 to -1.08, none of which had 95% confidence intervals that crossed zero, which indicates moderate to large decreases in muscle activity in patients with CAI compared with healthy controls.
  
  
  CONCLUSIONS
  Patients with CAI demonstrated decreased muscle activity of ankle, knee, and hip musculature during common functional rehabilitative tasks. Clinicians may benefit from implementing functional exercises for patients with CAI that target both distal and proximal muscles of the lower extremity.
authors.affiliation: Department of Kinesiology, University of Virginia, 210 Emmet Street South Charlottesville, VA 22904(∗). Electronic address: mf3de@virginia.edu.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Feger
authors.affiliation: Department of Kinesiology, University of Virginia, Charlottesville, VA(†).
authors.forename: Luke
authors.initials: L
authors.lastname: Donovan
authors.affiliation: Department of Kinesiology, University of Virginia, Charlottesville, VA(‡).
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Hart
authors.affiliation: Department of Kinesiology, University of Virginia, Charlottesville, VA(§).
authors.forename: Jay
authors.initials: J
authors.lastname: Hertel
mesh_terms: D000843:Ankle Joint / Q000503:physiopathology*; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004576:Electromyography; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000628:therapy*; D035002:Lower Extremity; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D016059:Range of Motion, Articular / Q000502:physiology*; D020127:Recovery of Function; D016896:Treatment Outcome; D055815:Young Adult