title: Effects of muscle cooling on the stiffness of the human gastrocnemius muscle in vivo.
abstract: OBJECTIVE
  The effects of muscle cooling on the stiffness of the human gastrocnemius muscle (GAS) were examined in vivo.
  
  
  METHODS
  The knee joint was passively extended from 90 to 0 degrees (0 degrees = full knee extended position) with a constant ankle angle of 10 degrees dorsiflexed position (0 degrees = the sole of the foot is approximately perpendicular to the anterior margin of the shaft of the tibia) in a control condition (room temperature of 18-23 degrees C) and a cooling condition (muscle temperature decreased by 5.8 +/- 1.7 degrees C after cooling using a cold water bath at a temperature of 5-8 degrees C for 60 min). The change in passive Achilles tendon force, muscle fascicle length of GAS and muscle temperature were measured (n = 6) during the motion.
  
  
  CONCLUSIONS
  GAS stiffness was significantly greater in the cooling condition (20 +/- 8 N/mm) than the control condition (18 +/- 8 N/mm). There was no cooling effect on the muscle slack length, beyond which passive muscle force arises. The maximum passive Achilles tendon force significantly increased by 19 +/- 20% after cooling. These results suggested that cooling increased the passive muscle force due to the increase in the muscle stiffness rather than the shift of the muscle slack length.
authors.affiliation: Consolidated Research Institute for Advanced Science and Medical Care, Waseda University, Tokorozawa, Japan. muraoka@aoni.waseda.jp
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Muraoka
authors.forename: Kohei
authors.initials: K
authors.lastname: Omuro
authors.forename: Taku
authors.initials: T
authors.lastname: Wakahara
authors.forename: Tadashi
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kanehisa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Fukunaga
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kanosue
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging / Q000502:physiology; D000328:Adult; D003080:Cold Temperature; D006801:Humans; D007036:Hypothermia, Induced; D007101:Immersion; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D014463:Ultrasonography