title: Biomechanical characteristics of the jump down of healthy subjects and patients with knee injuries.
abstract: OBJECTIVE
  The aim of this study is to investigate the drop jump performance of male patients who underwent ACLR and a control group using combined data acquisition system.
  
  
  METHODS
  A total of 28 male subjects aged 20 to 26 were studied: 22 did not show and were not diagnosed with any knee joint dysfunction (the control group) and six men who underwent ACLR of the left limb (group of patients). The control group was age, height and body mass matched. A data acquisition setup consisting of three independent modules including force platforms, position analysis system and electromyography was used. Subjects were jumping down from 0.1, 0.2, and 0.3 m step heights. The acquired signals were used to determine the ground reaction force, muscular activity, mass centre position, velocity and acceleration.
  
  
  RESULTS
  Statistically significant differences were found between the groups (t-test, p < 0.05) in the maximum vertical ground reaction force in the left limb for 0.2 and 0.3 m step heights. Differences in the muscle activity between the groups were found to be statistically significant (t-test, p < 0.05) before the jump, during the landing phase, and after the jump for selected muscle groups and step heights.
  
  
  CONCLUSIONS
  Combing the three independent measurement systems provided new information on drop jump biomechanics. The distribution of loads in different muscles was not uniform across the groups. Patients allocated more energy to control their motion and seemed to protect their operated limb by shifting the bodyweight to the healthy limb.
authors.affiliation: Wrocław University of Technology, Institute of Biomedical Engineering and Instrumentation, Wrocław, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Melińska
authors.affiliation: College of Physiotherapy in Wrocław, Wrocław, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Czamara
authors.affiliation: College of Physiotherapy in Wrocław, Wrocław, Poland.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Szuba
authors.affiliation: University of Zielona Góra, Faculty of Mechanical Engineering, Biomedical Engineering Group, Zielona Góra, Poland.
authors.forename: Romuald
authors.initials: R
authors.lastname: Będziński
mesh_terms: D000328:Adult; D005684:Gait; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D011930:Reaction Time; D013314:Stress, Mechanical; D013647:Task Performance and Analysis; D016474:Weight-Bearing; D055815:Young Adult