title: Assessment of musculo-articular and muscle stiffness in young and older men.
abstract: BACKGROUND
  The aim of this cross-sectional study was to concurrently assess musculo-articular stiffness (MAS) and muscle stiffness (MS) of the knee extensors in younger and older individuals.
  
  
  METHODS
  Fourteen young (22.1 ± 3.0 years old) and 12 older (65.4 ± 5.7 years old) men were tested for maximal voluntary contraction (MVC), rate of torque development (RTD), muscle thickness, MAS, and MS of knee extensors.
  
  
  RESULTS
  MVC, RTD, and muscle thickness were higher in the younger group (288.6 vs. 194.3 Nm, 1319.5 vs. 787.0 Nm s(-1), 23.1 vs. 17.7 mm, respectively, P < 0.05). MAS normalized to the load supported (30% of MVC) was not different between groups (87.9 vs. 88.5 Nm(-1) kg(-1)), whereas the older group exhibited a higher level of normalized MS (23.2 vs. 18.6 Nm(-1) kg(-1), P < 0.05).
  
  
  CONCLUSIONS
  Determinants of MS have been highlighted along with their role in elevated MS. The unaltered level of MAS, which is functionally important in an aging population, might be achieved through a decrease in tendon stiffness.
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Belfield, Dublin 4, Ireland. m.ditroilo@hull.ac.uk
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Ditroilo
authors.forename: Louise
authors.initials: L
authors.lastname: Cully
authors.forename: Colin A G
authors.initials: CA
authors.lastname: Boreham
authors.forename: Giuseppe
authors.initials: G
authors.lastname: De Vito
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D003430:Cross-Sectional Studies; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009135:Muscular Diseases / Q000175:diagnosis / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000502:physiology*; D013710:Tendons / Q000502:physiology; D019415:Torque; D055815:Young Adult