title: Functional in situ assessment of muscle contraction in wild-type and mdx mice.
abstract: BACKGROUND
  Reports of muscle testing are frequently limited to maximal force alone. The experiments reported here show that force generation and relaxation rates can be obtained from the same experiments and provide a more complete functional characterization.
  
  
  METHODS
  Partial in situ testing was performed on the tibialis anterior of young wild-type (WT) mice, young mdx mice, and old mdx mice. Force, force generation rate, and relaxation rates were measured during a fatigue test, 2 frequency-force tests, and a passive tension test.
  
  
  RESULTS
  We measured increased force but decreased force generation rate in WT compared with mdx muscles, and increased force but decreased relaxation rate of old compared with young mdx muscles. Young mdx muscles were the most sensitive to increases in passive tension.
  
  
  CONCLUSIONS
  These measurements offer an improved understanding of muscle capability and are readily acquired by further analysis of the same tests used to obtain force measurements.
authors.affiliation: Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois, 60612, USA.
authors.forename: Tammy
authors.initials: T
authors.lastname: Tamayo
authors.affiliation: Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois, 60612, USA.
authors.forename: Eben
authors.initials: E
authors.lastname: Eno
authors.affiliation: Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois, 60612, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Madrigal
authors.affiliation: Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois, 60612, USA.
authors.forename: Ahlke
authors.initials: A
authors.lastname: Heydemann
authors.affiliation: Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois, 60612, USA.
authors.forename: Kelly
authors.initials: K
authors.lastname: García
authors.affiliation: Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois, 60612, USA.
authors.forename: Jesús
authors.initials: J
authors.lastname: García
mesh_terms: D000367:Age Factors; D000818:Animals; D055592:Biophysical Phenomena / Q000235:genetics; D004558:Electric Stimulation; D005221:Fatigue / Q000209:etiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D009119:Muscle Contraction / Q000235:genetics / Q000502:physiology*; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology*; D009137:Muscular Dystrophy, Animal / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology*
keywords: fatigue; frequency-force; muscle testing; muscular dystrophy; passive tension tolerance