title: Determining minimal stimulus intensity for mechanomyographic analysis.
abstract: BACKGROUND
  Mechanomyography (MMG) has recently shown promise in monitoring recovery of injured muscles. However, delivering a maximal percutaneous neuromuscular stimulus (PNS) could potentially be painful on severely damaged muscles. The aim of this paper was to determine whether delivering a sub-maximal PNS could still obtain accurate MMG recordings of muscle contraction time (Tc). The effect of muscle architecture on determining the minimal level of current was also investigated.
  
  
  METHODS
  Six muscles were investigated; 5 lower limb and the 1st dorsal interosseous. A 'current ramp' procedure was performed to determine minimal stimulus intensity required for accurate Tc recordings. A current ramp entails beginning at a low current (30mA) and increasing in increments of 10mA until a maximal muscle contraction is observed.
  
  
  RESULTS
  For lower limb muscles, 130mA was the largest current required to obtain accurate Tc recordings in at least 95% of the population. This was up to a 50% reduction in the amount of current delivered for some muscles. Fibre type distribution showed the greatest relationship with mean minimum current.
  
  
  CONCLUSIONS
  Future studies investigating injured or uninjured muscles via MMG, could use these submaximal currents to obtain accurate MMG recordings, whilst improving patient comfort and reducing experiment duration.
authors.affiliation: The University of Queensland, School of Biomedical Sciences, Department of Anatomy & Developmental Biology, St. Lucia 4072, Australia. Electronic address: danijel.tosovic@uqconnect.edu.au.
authors.forename: Danijel
authors.initials: D
authors.lastname: Tosovic
authors.affiliation: The University of Queensland, School of Biomedical Sciences, Department of Anatomy & Developmental Biology, St. Lucia 4072, Australia.
authors.forename: Laura
authors.initials: L
authors.lastname: Seidl
authors.affiliation: The University of Queensland, School of Biomedical Sciences, Department of Anatomy & Developmental Biology, St. Lucia 4072, Australia.
authors.forename: Estifanos
authors.initials: E
authors.lastname: Ghebremedhin
authors.affiliation: The University of Queensland, School of Biomedical Sciences, Department of Anatomy & Developmental Biology, St. Lucia 4072, Australia.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Brown
mesh_terms: D006801:Humans; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*; D009213:Myography / Q000379:methods* / Q000592:standards
keywords: Contraction time; Injury; Mechanomyography; Muscle; Stimulation