title: In vivo myograph measurement of muscle contraction at optimal length.
abstract: BACKGROUND
  Current devices for measuring muscle contraction in vivo have limited accuracy in establishing and re-establishing the optimum muscle length. They are variable in the reproducibility to determine the muscle contraction at this length, and often do not maintain precise conditions during the examination. Consequently, for clinical testing only semi-quantitative methods have been used.
  
  
  METHODS
  We present a newly developed myograph, an accurate measuring device for muscle contraction, consisting of three elements. Firstly, an element for adjusting the axle of the device and the physiological axis of muscle contraction; secondly, an element to accurately position and reposition the extremity of the muscle; and thirdly, an element for the progressive pre-stretching and isometric locking of the target muscle. Thus it is possible to examine individual in vivo muscles in every pre-stretched, specified position, to maintain constant muscle-length conditions, and to accurately re-establish the conditions of the measurement process at later sessions.
  
  
  RESULTS
  In a sequence of experiments the force of contraction of the muscle at differing stretching lengths were recorded and the forces determined. The optimum muscle length for maximal force of contraction was established. In a following sequence of experiments with smaller graduations around this optimal stretching length an increasingly accurate optimum muscle length for maximal force of contraction was determined. This optimum length was also accurately re-established at later sessions.
  
  
  CONCLUSIONS
  We have introduced a new technical solution for valid, reproducible in vivo force measurements on every possible point of the stretching curve. Thus it should be possible to study the muscle contraction in vivo to the same level of accuracy as is achieved in tests with in vitro organ preparations.
authors.affiliation: Department of Anaesthesiology, Hannover Medical School, Carl-Neuberg-Str, 1, D-30625 Hannover, Germany. Rahe-Meyer.Niels@MH-Hannover.de
authors.forename: Niels
authors.initials: N
authors.lastname: Rahe-Meyer
authors.forename: Christian
authors.initials: C
authors.lastname: Weilbach
authors.forename: Matthias
authors.initials: M
authors.lastname: Karst
authors.forename: Matthias
authors.initials: M
authors.lastname: Pawlak
authors.forename: Aminul
authors.initials: A
authors.lastname: Ahmed
authors.forename: Siegfried
authors.initials: S
authors.lastname: Piepenbrock
authors.forename: Michael
authors.initials: M
authors.lastname: Winterhalter
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009213:Myography / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D014159:Transducers