title: A novel method to attain sinusoidal mechanical responses from single motor units.
abstract: BACKGROUND
  The relationship between output force and motor command depends on the intrinsic dynamic responses of motor units (MUs), which can be characterized by evoking accurate sinusoidal force responses at different frequencies. In this study we sought to determine whether sinusoidal modulation of the stimulation rate of single MUs results in reliable sinusoidal force changes.
  
  
  METHODS
  Single axons of rat ventral roots were stimulated electrically by changing the pulse rate sinusoidally at different frequency modulation (0.4-1.0-2.0-4.0 Hz for slow, 1.0-2.0-4.0-7.0 Hz for fast MUs). The twitching sinusoidal force signal was interpolated. We calculated harmonic distortion (HD) and the correlation coefficient (r) between theoretical sines and interpolated signals.
  
  
  RESULTS
  HD was always <5%, and r was always >0.97.
  
  
  CONCLUSIONS
  The HD and r-values obtained indicate highly reliable sinusoidal responses, which supports the potential use of this method to further characterize the dynamic behavior of single MUs.
authors.affiliation: Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Gobbo
authors.forename: Jan
authors.initials: J
authors.lastname: Celichowski
authors.forename: Piotr
authors.initials: P
authors.lastname: Krutki
authors.forename: Hanna
authors.initials: H
authors.lastname: Drzymała-Celichowska
authors.forename: Moshe
authors.initials: M
authors.lastname: Solomonow
authors.forename: Claudio
authors.initials: C
authors.lastname: Orizio
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena / Q000502:physiology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D013126:Spinal Nerve Roots / Q000166:cytology
keywords: dynamic response; electrical stimulation; harmonic distortion; muscle modeling; muscle-tendon unit signal interpolation