title: The prediction of neck extensor force using surface electromyography.
abstract: BACKGROUND
  The relationship between muscular force and electromyography (EMG) has been investigated by numerous researchers. EMG has not previously been used as a means of estimating force in the cervical erector spinae (CES).
  
  
  OBJECTIVE
  Use EMG of the CES musculature to indirectly predict neck extension force.
  
  
  METHODS
  Isometric contractions of the CES muscles were studied at increasing levels of contractile force across all participants (n= 12) to produce an individualised force-EMG relationship. The method of least squares was used to determine the linear regression trend line for the force-EMG relationship. The validity of these individual `correlation curves' was demonstrated through further, blinded, investigation.
  
  
  RESULTS
  A linear relationship was identified for the individualised correlation curves that gained in strength for < 50% maximum voluntary contraction (MVC; R2> 0.8 for 80% of trials). The prediction of muscle force from the correlation curves was found to be statistically similar to the equivalent experimental data (p> 0.05). Given the tendency of EMG to slightly overestimate force in most cases, an adjustment coefficient was calculated to reduce the error in the predicted force data.
  
  
  CONCLUSIONS
  This study reports a validated method using EMG to indirectly acquire CES muscular force, which has application for clinicians and research scientists working in fields including sport and rehabilitation.
authors.affiliation: Bioengineering Research Group, School of Engineering, Cardiff University, Cardiff, UK.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Swaminathan
authors.affiliation: Faculty of Health and Social Sciences, Bournemouth University, Bournemouth, Dorset, UK.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Williams
authors.affiliation: Bioengineering Research Group, School of Engineering, Cardiff University, Cardiff, UK.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Jones
authors.affiliation: Bioengineering Research Group, School of Engineering, Cardiff University, Cardiff, UK.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Theobald
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009334:Neck Muscles / Q000502:physiology*
keywords: EMG; cervical spine; force; muscle