Reliability of normalisation methods for EMG analysis of neck muscles

Article type: Research Article

Authors: Netto, Kevin J. | Burnett, Angus F.

Affiliations: School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia | School of Physiotherapy, Curtin University of Technology, WA, Australia

Note: [] Corresponding author. Tel.: +61 8 6304 5860; Fax: +61 8 6304 5036; E-mail: K.Netto@curtin.edu.au

Abstract: Acceptable reliability of normalisation contractions in electromyography (EMG) is paramount for testing conducted over a number of days or if normal laboratory strength testing equipment is unavailable. This study examined the reliability of maximal voluntary isometric contractions (MVIC) and sub-maximal (60%) isometric contractions for use in neck muscle EMG studies. Surface EMG was recorded bilaterally from eight sites around the neck at C4/5 level from five healthy male subjects. Subjects performed MVIC and sub-maximal normalisation contractions using an isokinetic dynamometer (ID) and a portable cable dynamometer with attached strain gauge (PCD) in addition to a MVIC against a manual resistance (MR). Subjects were tested in flexion, extension, left and right lateral bending and were retested by the same tester within a two-week period. Intra class correlation co-efficients (ICC) were calculated for each testing method and contraction direction and a mean ICC was calculated across all contraction directions. All normalisation methods produced excellent within-day reliability (mean ICC >0.80) but only the MVICs using the ID and PCD had acceptable reliability when assessed between-days. This study confirmed the validity of using MVICs elicited using the ID and PCD as reliable reference contractions for the normalisation of neck EMG.

Keywords: Electromyography, neck, cervical, reliability, normalisation

Journal: Work, vol. 26, no. 2, pp. 123-130, 2006