title: Does knee joint cooling change in vivo patellar tendon mechanical properties?
abstract: OBJECTIVE
  This study aimed to assess the influence of knee joint cooling on the in vivo mechanical properties of the patellar tendon.
  
  
  METHODS
  Twenty young, healthy women volunteered for the study. B-mode ultrasonography was used to record patellar tendon elongation during isometric ramp contraction of the knee extensors (5-7 s, 90° knee angle) and calculate tendon stiffness. Skin temperature was measured by infrared thermometry. Data were acquired before and after 30 min of local icing of the knee joint and compared by paired samples t-tests.
  
  
  RESULTS
  After cold exposure, skin temperature as measured over the patellar tendon dropped by 16.8 ± 2.0 °C. Tendon stiffness increased from 2189 ± 551 to 2705 ± 902 N mm(-1) (+25 %, p = 0.007). Tendon strain decreased by 9 % (p = 0.004). A small, albeit significant reduction in maximum tendon force was observed (-3.3 %, p = 0.03).
  
  
  CONCLUSIONS
  Knee cooling is associated with a significant increase in patellar tendon stiffness. The observed tendon stiffening may influence the operating range of sarcomeres, possibly limiting the maximal force generation capacity of knee extensor muscles. In addition, a stiffer tendon might benefit rate of force development, thus countering the loss in explosiveness typically described for cold muscles.
authors.affiliation: GENUD Toledo Research Group, University of Castilla-La Mancha, Avda. Carlos III s/n, 45071, Toledo, Spain.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Alegre
authors.affiliation: Centre of Technology of Ski and Alpine Sport, Fürstenweg 187, Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Hasler
authors.affiliation: Centre of Technology of Ski and Alpine Sport, Fürstenweg 187, Innsbruck, Austria.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wenger
authors.affiliation: Department of Sport Science, University of Innsbruck, Fürstenweg 185, Innsbruck, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Nachbauer
authors.affiliation: Department of Sport Science, University of Innsbruck, Fürstenweg 185, Innsbruck, Austria. robert.csapo@uibk.ac.at.
authors.forename: Robert
authors.initials: R
authors.lastname: Csapo
mesh_terms: D001831:Body Temperature / Q000502:physiology; D003080:Cold Temperature; D055119:Elastic Modulus / Q000502:physiology; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods*; D007719:Knee Joint / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D017847:Patellar Ligament / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012881:Skin Temperature / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology; D014463:Ultrasonography / Q000379:methods; D055815:Young Adult
keywords: Cryotherapy; Material properties; Tendon deformation; Ultrasonography