title: Alterations to landing technique and patellar tendon loading in response to fatigue.
abstract: OBJECTIVE
  Fatigue may contribute to knee joint injuries, such as patellar tendinopathy, by increasing joint loading and altering lower limb landing technique, which in turn may increase tissue loading. This study aimed to investigate the effect of lower limb muscle fatigue on the landing technique and patellar tendon loads generated during the horizontal and vertical landing phases of a stop-jump task. It was hypothesized that muscle fatigue would increase patellar tendon loading and alter the landing technique displayed during the horizontal, but not the vertical, landing phase of the stop-jump task.
  
  
  METHODS
  Sixteen men, recruited from team sports involving repetitive landing, performed repeated trials of a stop-jump task. During each trial, the participants' ground reaction forces and electromyographic activity of seven lower limb muscles were recorded, three-dimensional kinematics measured, and peak patellar tendon force (FPT) calculated.
  
  
  RESULTS
  When fatigued, participants generated a significantly lower FPT and FPT loading rate, despite a higher vertical ground reaction force (FV) and FV loading rate, during the horizontal landing phase of the stop-jump task. During the vertical landing phase, participants displayed only minor changes to the kinetics and kinematics of their landing in response to fatigue, although fatigue caused substantial alterations to their lower limb muscle activation patterns during landing.
  
  
  CONCLUSIONS
  During the horizontal landing phase of the stop-jump task, participants decreased their patellar tendon load when they were fatigued by altering their lower limb landing technique, including a reduced net knee joint extension moment associated with less knee and hip flexion. This decrease in patellar tendon loading when fatigued may be an inherent protective strategy to potentially decrease loading of the tendon during repetitive landing.
authors.affiliation: 1School of Human Movement Studies, Charles Sturt University, New South Wales, AUSTRALIA, 2Biomechanics Research Laboratory, University of Wollongong, New South Wales, AUSTRALIA; 3Australian Institute of Sport, Canberra, Australian Capital Territory, AUSTRALIA; and 4Department of Physiotherapy, Monash University, Clayton, Victoria, AUSTRALIA.
authors.forename: Suzi
authors.initials: S
authors.lastname: Edwards
authors.forename: Julie R
authors.initials: JR
authors.lastname: Steele
authors.forename: Craig R
authors.initials: CR
authors.lastname: Purdam
authors.forename: Jill L
authors.initials: JL
authors.lastname: Cook
authors.forename: Deirdre E
authors.initials: DE
authors.lastname: McGhee
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005080:Exercise Test; D006801:Humans; D035002:Lower Extremity / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D017847:Patellar Ligament / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult