title: Effects of Experimental Anterior Knee Pain on Muscle Activation During Landing and Jumping Performed at Various Intensities.
abstract: BACKGROUND
  Although knee pain is common, some facets of this pain are unclear. The independent effects (ie, independent from other knee injury or pathology) of knee pain on neural activation of lower-extremity muscles during landing and jumping have not been observed.
  
  
  OBJECTIVE
  To investigate the independent effects of knee pain on lower-extremity muscle (gastrocnemius, vastus medialis, medial hamstrings, gluteus medius, and gluteus maximus) activation amplitude during landing and jumping, performed at 2 different intensities.
  
  
  METHODS
  Laboratory-based, pretest, posttest, repeated-measures design, where all subjects performed both data-collection sessions.
  
  
  METHODS
  Thirteen able-bodied subjects performed 2 different land and jump tasks (forward and lateral) under 2 different conditions (control and pain), at 2 different intensities (high and low). For the pain condition, experimental knee pain was induced via a hypertonic saline injection into the right infrapatellar fat pad. Functional linear models were used to evaluate the influence of experimental knee pain on muscle-activation amplitude throughout the 2 land and jump tasks.
  
  
  RESULTS
  Experimental knee pain independently altered activation for all of the observed muscles during various parts of the 2 different land and jump tasks. These activation alterations were not consistently influenced by task intensity.
  
  
  CONCLUSIONS
  Experimental knee pain alters activation amplitude of various lower-extremity muscles during landing and jumping. The nature of the alteration varies between muscles, intensities, and phases of the movement (ie, landing and jumping). Generally, experimental knee pain inhibits the gastrocnemius, medial hamstring, and gluteus medius during landing while independently increasing activation of the same muscles during jumping.
authors.forename: Jihong
authors.initials: J
authors.lastname: Park
authors.forename: W Matt
authors.initials: WM
authors.lastname: Denning
authors.forename: Jordan D
authors.initials: JD
authors.lastname: Pitt
authors.forename: Devin
authors.initials: D
authors.lastname: Francom
authors.forename: J Ty
authors.initials: JT
authors.lastname: Hopkins
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Seeley
mesh_terms: D001696:Biomechanical Phenomena; D005080:Exercise Test; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D046788:Patellofemoral Pain Syndrome / Q000503:physiopathology*; D012720:Severity of Illness Index; D055815:Young Adult
keywords: arthrogenic muscle inhibition; electromyography; joint pain; neural activation