title: Dynamic Frequency Analyses of Lower Extremity Muscles during Sit-To-Stand Motion for the Patients with Knee Osteoarthritis.
abstract: OBJECTIVE
  Muscle activities during the sit-to-stand motion (STS) are characterized by coordinated movements between hip extensors and knee extensors. However, previous reports regarding the STS and lower extremity muscle activities have focused on some quantitative assessment, but little qualitative research. This study aimed to examine the muscle activities of the lower extremity both quantitatively and qualitatively.
  
  
  METHODS
  Study participants included 13 patients with knee osteoarthritis (knee OA) and 11 age-matched asymptomatic controls. The task was STS from a chair with a height-adjustable seat. EMG activities were acquired using surface electromyogram. The root mean square signals normalized as a percentage of maximum voluntary isometric contraction values (RMS%MVC) and the mean power frequency (MPF) were calculated.
  
  
  RESULTS
  During STS, knee OA patients had increased RMS%MVC of the vastus medialis and raised MPF of the rectus femoris before buttocks-off.
  
  
  CONCLUSIONS
  These findings suggest that STS of knee OA patients not only increased relative muscle activity of the vastus medialis, but also enlisted the rectus femoris in knee extension to improve muscle contraction force by activating more type II fibers to accomplish buttocks-off.
authors.affiliation: Department of Biomechanics, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima-shi, Hiroshima, Japan.|Center for Advanced Practice and Research of Rehabilitation, Hiroshima University, Hiroshima-shi, Hiroshima, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Anan
authors.affiliation: Department of Biomechanics, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima-shi, Hiroshima, Japan.|Center for Advanced Practice and Research of Rehabilitation, Hiroshima University, Hiroshima-shi, Hiroshima, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Shinkoda
authors.affiliation: Nagoya University Hospital, Nagoya-shi, Nagoya, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Midorii Orthopaedics Joint Reconstruction & Arthroscopy, Hiroshima-shi, Hiroshima, Japan.
authors.forename: Masahide
authors.initials: M
authors.lastname: Yagi
authors.affiliation: Hiroshima International University, Higashi-Hiroshima, Hiroshima, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Kito
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology*; D054850:Osteophyte / Q000209:etiology / Q000503:physiopathology; D011187:Posture; D016474:Weight-Bearing