title: Six weeks' aerobic retraining after two weeks' immobilization restores leg lean mass and aerobic capacity but does not fully rehabilitate leg strength in young and older men.
abstract: OBJECTIVE
  To determine the effect of aerobic retraining as rehabilitation after short-term leg immobilization on leg strength, leg work capacity, leg lean mass, leg muscle fibre type composition and leg capillary supply, in young and older men.Subjects and design: Seventeen young (23 ± 1 years) and 15 older (68 ± 1 [standard error of the mean; SEM] years) men had one leg immobilized for 2 weeks, followed by 6 weeks' bicycle endurance retraining.
  
  
  METHODS
  Maximal voluntary contraction, leg work capacity (Wmax), and leg lean mass by dual energy X-ray absorptiometry were measured at inclusion, after immobilization and after 3 and 6 weeks' retraining. Muscle biopsies were evaluated for fibre type, fibre area, and capillarization.
  
  
  RESULTS
  Immobilization decreased maximal voluntary contraction (-28 ± 6% and -23 ± 3%); Wmax (-13 ± 5% and -9 ± 4%) and leg lean mass (only in young, -485 ± 105g) in young and older men, respectively. Six weeks' retraining increased maximal voluntary contraction (34 ± 8% and 17 ± 6%), Wmax (33 ± 5% and 20 ± 5%) and leg lean mass (only in young 669 ± 69 g) in young and older men, respectively, compared with the immobilized value.
  
  
  CONCLUSIONS
  Short-term leg immobilization had marked effects on leg strength, and work capacity and 6 weeks' retraining was sufficient to increase, but not completely rehabilitate, muscle strength, and to rehabilitate aerobic work capacity and leg lean mass (in the young men).
authors.forename: Andreas
authors.initials: A
authors.lastname: Vigelsø
authors.forename: Martin
authors.initials: M
authors.lastname: Gram
authors.forename: Caroline
authors.initials: C
authors.lastname: Wiuff
authors.forename: Jesper L
authors.initials: JL
authors.lastname: Andersen
authors.forename: Jørn W
authors.initials: JW
authors.lastname: Helge
authors.forename: Flemming
authors.initials: F
authors.lastname: Dela
mesh_terms: D000328:Adult; D000368:Aged; D002196:Capillaries / Q000502:physiology; D005081:Exercise Therapy; D006801:Humans; D007103:Immobilization; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply; D010807:Physical Endurance / Q000502:physiology