title: Knee joint effusion and cryotherapy alter lower chain kinetics and muscle activity.
abstract: BACKGROUND
  Cryotherapy has been shown to disinhibit the quadriceps muscle after joint effusion by a resting measure (Hoffmann reflex) of motor recruitment. I sought to determine whether cryotherapy-induced motor recruitment changes resulted in subsequent changes in functional movement.
  
  
  OBJECTIVE
  To quantify muscle recruitment changes and knee joint function after joint effusion and subsequent joint cryotherapy.
  
  
  METHODS
  A 3 x 4 multivariate mixed-model design was used to compare groups (normative, effusion/control, effusion/cryotherapy) across time (preinjection, postinjection, 30 minutes postinjection, and 60 minutes postinjection).
  
  
  METHODS
  Human performance laboratory.
  
  
  METHODS
  Forty-five volunteers (26 males, 19 females; age = 21 +/- 2 years, height = 174.8 +/- 10.2 cm, mass = 78.1 +/- 15.4 kg).
  
  
  METHODS
  Experimental joint effusion was used to elicit inhibition of the quadriceps muscle. Cryotherapy was a treatment intervention.
  
  
  METHODS
  Lower chain peak joint torque, peak and average power, knee anterior joint reaction force, and average and peak vastus medialis, vastus lateralis, medial hamstrings, and gastrocnemius muscle normalized electromyographic activity were collected during the extension phase of a seated, recumbent stepping motion with a resistance of 36% of 1-repetition maximum and a controlled cadence of 1.5 Hz.
  
  
  RESULTS
  Decreases in peak torque and peak power were observed after effusion, whereas no decrease was observed over time in the cryotherapy or normative groups. A decrease in peak vastus lateralis activity was also noted after effusion relative to other groups. Also, the effusion/cryotherapy group had a greater knee anterior joint reaction force relative to the effusion/control and normative groups after effusion.
  
  
  CONCLUSIONS
  Joint cryotherapy negated movement deficiencies represented by knee peak torque and power decreases. This could be due to facilitated vastus lateralis activation relative to other groups.
authors.affiliation: Brigham Young University, Provo, UT 84602-2205, USA. tyhopkins@byu.edu
authors.forename: J Ty
authors.initials: JT
authors.lastname: Hopkins