title: Deterioration of muscle function after 21-day forearm immobilization.
abstract: OBJECTIVE
  Although it is well known that immobilization causes muscle atrophy, most immobilization models have examined lower limbs, and little is known about the forearm. The purpose of this study was to determine whether forearm immobilization produces changes in muscle morphology and function.
  
  
  METHODS
  Six healthy males (age: 21.5 +/- 1.4, mean +/- SD) participated in this study. The nondominant arm was immobilized with a cast (CAST) for 21 d, and the dominant arm was measured as the control (CONT). The forearm cross-sectional area (CSA) and circumference were measured as muscle morphology. Maximum grip strength, forearm muscle oxidative capacity, and dynamic grip endurance were measured as muscle function. Magnetic resonance (MR) imaging was used to measure CSA, and 31phosphorus MR spectroscopy was used to measure time constant (Tc) for phosphocreatine (PCr) recovery after submaximal exercise (PCr-Tc). Grip endurance was expressed by the number of handgrip contractions at 30% maximum grip strength load. All measurements were taken before and after the immobilization.
  
  
  RESULTS
  After the 21-d forearm immobilization, no changes were seen for each measurement in CONT. CSA and the circumference showed no significant changes in CAST. However, maximum grip strength decreased by 18% (P < 0.05), PCr-Tc was prolonged by 45% (P < 0.05), and the grip endurance at the absolute load was reduced by 19% (P < 0.05) for CAST.
  
  
  CONCLUSIONS
  In this model, 21-d forearm immobilization caused no significant changes in forearm muscle morphology, but the muscle function showed remarkable deterioration ranging from 18 to 45%.
authors.affiliation: Department of Preventive Medicine and Public Health, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan. Ayakitahar@aol.com
authors.forename: Aya
authors.initials: A
authors.lastname: Kitahara
authors.forename: Takafumi
authors.initials: T
authors.lastname: Hamaoka
authors.forename: Norio
authors.initials: N
authors.lastname: Murase
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Homma
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kurosawa
authors.forename: Chihoko
authors.initials: C
authors.lastname: Ueda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nagasawa
authors.forename: Shiro
authors.initials: S
authors.lastname: Ichimura
authors.forename: Mayuko
authors.initials: M
authors.lastname: Motobe
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yashiro
authors.forename: Shouichi
authors.initials: S
authors.lastname: Nakano
authors.forename: Toshihito
authors.initials: T
authors.lastname: Katsumura
mesh_terms: D000328:Adult; D002370:Casts, Surgical; D005542:Forearm; D018737:Hand Strength; D006801:Humans; D007103:Immobilization; D008297:Male; D009132:Muscles / Q000503:physiopathology*; D009133:Muscular Atrophy; D010084:Oxidation-Reduction; D010807:Physical Endurance