title: Effect of limiting ankle-dorsiflexion range of motion on lower extremity kinematics and muscle-activation patterns during a squat.
abstract: BACKGROUND
  Limitations in gastrocnemius/soleus flexibility that restrict ankle dorsiflexion during dynamic tasks have been reported in individuals with patellofemoral pain (PFP) and are theorized to play a role in its development.
  
  
  OBJECTIVE
  To determine the effect of restricted ankle-dorsiflexion range of motion (ROM) on lower extremity kinematics and muscle activity (EMG) during a squat. The authors hypothesized that restricted ankle-dorsiflexion ROM would alter knee kinematics and lower extremity EMG during a squat.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  30 healthy, recreationally active individuals without a history of lower extremity injury.
  
  
  METHODS
  Each participant performed 7 trials of a double-leg squat under 2 conditions: a no-wedge condition (NW) with the foot flat on the floor and a wedge condition (W) with a 12° forefoot angle to simulate reduced plantar-flexor flexibility.
  
  
  METHODS
  3-dimensional hip and knee kinematics, medial knee displacement (MKD), and ankle-dorsiflexion angle. EMG of vastus medialis oblique (VMO), vastus lateralis (VL), lateral gastrocnemius (LG), and soleus (SOL). One-way repeated-measures ANOVAs were performed to determine differences between the W and NW conditions.
  
  
  RESULTS
  Compared with the NW condition, the wedge produced decreased peak knee flexion (P < .001, effect size [ES] = 0.81) and knee-flexion excursion (P < .001, ES = 0.82) while producing increased peak ankle dorsiflexion (P = .006, ES = 0.31), ankle-dorsiflexion excursion (P < .001, ES = 0.31), peak knee-valgus angle (P = .02, ES = 0.21), and MKD (P < .001, ES = 2.92). During the W condition, VL (P = 0.002, ES = 0.33) and VMO (P = .049, ES = 0.20) activity decreased while soleus activity increased (P = .03, ES = 0.64) compared with the NW condition. No changes were seen in hip kinematics (P > .05).
  
  
  CONCLUSIONS
  Altering ankle-dorsiflexion starting position during a double-leg squat resulted in increased knee valgus and MKD, as well as decreased quadriceps activation and increased soleus activation. These changes are similar to those seen in people with PFP.
authors.affiliation: Dept of Athletics, University of Richmond, Richmond, VA, USA.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Macrum
authors.forename: David Robert
authors.initials: DR
authors.lastname: Bell
authors.forename: Michelle
authors.initials: M
authors.lastname: Boling
authors.forename: Michael
authors.initials: M
authors.lastname: Lewek
authors.forename: Darin
authors.initials: D
authors.lastname: Padua
mesh_terms: D000293:Adolescent; D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D055815:Young Adult