Reliability of quadriceps surface electromyography measurements is improved by two vs. single site recordings

T. G. Balshaw, A. Fry, T. M. Maden-Wilkinson, P. W. Kong, J. P. Folland

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Purpose: The reliability of surface electromyography (sEMG) is typically modest even with rigorous methods, and therefore further improvements in sEMG reliability are desirable. This study compared the between-session reliability (both within participant absolute reliability and between-participant relative reliability) of sEMG amplitude from single vs. average of two distinct recording sites, for individual muscle (IM) and whole quadriceps (WQ) measures during voluntary and evoked contractions. Methods: Healthy males (n = 20) performed unilateral isometric knee extension contractions: voluntary maximum and submaximum (60%), as well as evoked twitch contractions on two separate days. sEMG was recorded from two distinct sites on each superficial quadriceps muscle. Results: Averaging two recording sites vs. using single site measures improved reliability for IM and WQ measurements during voluntary (16–26% reduction in within-participant coefficient of variation, CVW) and evoked contractions (40–56% reduction in CVW). Conclusions: For sEMG measurements from large muscles, averaging the recording of two distinct sites is recommended as it improves within-participant reliability. This improved sensitivity has application to clinical and research measurement of sEMG amplitude.

Original languageEnglish
Pages (from-to)1085-1094
Number of pages10
JournalEuropean Journal of Applied Physiology
Issue number6
StatePublished - 1 Jun 2017
Externally publishedYes


  • Coefficient of variation
  • Evoked muscle response
  • Intraclass correlation coefficient
  • Knee extension
  • Peripheral nerve stimulation
  • Voluntary muscle contraction


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