Comparison of EMG activity of medial and lateral hamstrings during isometric contractions at various cuff weight loads

Ira M. Fiebert, Neil I. Spielholz, E. Brooks Applegate, Christina Fox, Jonathan Jaro, Laurel Joel, Laurie Raper

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Since both the medial head (MH) and lateral head (LH) of the hamstring muscles contribute to knee flexion, this study investigated whether the relative electrical activity of these heads remained constant with respect to each other or changed during isometric contractions at five different resistance levels. The relative electrical activity of these two heads was determined by comparing their integrated EMG (iEMG). Forty-two volunteers with no history of right lower extremity injury or disease, between the ages of 18 and 35, were studied. Following motor point location, surface electrodes were placed over the MH and LH. Subjects, positioned prone, flexed the knee to 45° using a sawhorse as a tactile cue to help maintain this position. Three recordings, 8 s in length, were taken at each subject's maximum isometric contraction and then using cuff weights of 1, 3, 5, and 7% of their body weight. The average of the three recordings was used in the analysis. During maximum isometric contraction (at 45° of knee flexion), the LH contributes a significantly greater percent of the total iEMG (63.4%) than the MH (P<0.0001). Furthermore, within the four submaximal levels tested, the LH's contribution was significantly greater than the MH (P<0.01). During submaximal isometric contractions, the LH percent contribution to total iEMG was less than its contribution during maximal isometric contraction, all P values <0.005. As a result, during these same submaximal isometric contractions, the MH contribution to total iEMG was greater than its contribution during maximal isometric contraction, all P values <0.005).

Original languageEnglish (US)
Pages (from-to)145-150
Number of pages6
JournalKnee
Volume8
Issue number2
DOIs
StatePublished - Jan 1 2001

Keywords

  • iEMG
  • Lateral hamstring
  • Medial hamstring

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine

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