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

• Published in: The knee 2001-06, Vol.8 (2), p.145-150
• Main Authors: Fiebert, Ira M, Spielholz, Neil I, Applegate, E.Brooks, Fox, Christina, Jaro, Jonathan, Joel, Laurel, Raper, Laurie
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Analysis of Variance; Electromyography; Female; Humans; iEMG; Isometric Contraction - physiology; Knee Joint - physiology; Lateral hamstring; Male; Medial hamstring; Muscle, Skeletal - physiology; Range of Motion, Articular - physiology; Torque; Weight-Bearing - physiology
• ISSN: 0968-0160; 1873-5800
• DOI: 10.1016/S0968-0160(00)00079-X

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