title: Instruction and jump-landing kinematics in college-aged female athletes over time.
abstract: BACKGROUND
  Instruction can be used to alter the biomechanical movement patterns associated with anterior cruciate ligament (ACL) injuries.
  
  
  OBJECTIVE
  To determine the effects of instruction through combination (self and expert) feedback or self-feedback on lower extremity kinematics during the box-drop-jump task, running-stop-jump task, and sidestep-cutting maneuver over time in college-aged female athletes.
  
  
  METHODS
  Randomized controlled clinical trial.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Forty-three physically active women (age = 21.47 ± 1.55 years, height = 1.65 ± 0.08 m, mass = 63.78 ± 12.00 kg) with no history of ACL or lower extremity injuries or surgery in the 2 months before the study were assigned randomly to 3 groups: self-feedback (SE), combination feedback (CB), or control (CT).
  
  
  METHODS
  Participants performed a box-drop-jump task for the pretest and then received feedback about their landing mechanics. After the intervention, they performed an immediate posttest of the box-drop-jump task and a running-stop-jump transfer test. Participants returned 1 month later for a retention test of each task and a sidestep-cutting maneuver. Kinematic data were collected with an 8-camera system sampled at 500 Hz.
  
  
  METHODS
  The independent variables were feedback group (3), test time (3), and task (3). The dependent variables were knee- and hip-flexion, knee-valgus, and hip- abduction kinematics at initial contact and at peak knee flexion.
  
  
  RESULTS
  For the box-drop-jump task, knee- and hip-flexion angles at initial contact were greater at the posttest than at the retention test (P < .001). At peak knee flexion, hip flexion was greater at the posttest than at the pretest (P = .003) and was greater at the retention test than at the pretest (P = .04); knee valgus was greater at the retention test than at the pretest (P = .03) and posttest (P = .02). Peak knee flexion was greater for the CB than the SE group (P = .03) during the box-drop-jump task at posttest. For the running-stop-jump task at the posttest, the CB group had greater peak knee flexion than the SE and CT (P ≤ .05).
  
  
  CONCLUSIONS
  Our results suggest that feedback involving a combination of self-feedback and expert video feedback with oral instruction effectively improved lower extremity kinematics during jump-landing tasks.
authors.affiliation: Department of Human Movement Sciences, Old Dominion University, Norfolk, VA, USA.
authors.forename: Jena
authors.initials: J
authors.lastname: Etnoyer
authors.forename: Nelson
authors.initials: N
authors.lastname: Cortes
authors.forename: Stacie I
authors.initials: SI
authors.lastname: Ringleb
authors.forename: Bonnie L
authors.initials: BL
authors.lastname: Van Lunen
authors.forename: James A
authors.initials: JA
authors.lastname: Onate
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D025461:Feedback, Physiological; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D010806:Physical Education and Training; D055815:Young Adult