Influence of contraction intensity, muscle, and gender on median frequency of the quadriceps femoris

• Published in: Journal of applied physiology (1985) Vol. 90; no. 3; pp. 804 - 810
• Main Authors: Pincivero, Danny M, Campy, Robert M, Salfetnikov, Yuliya, Bright, Ashley, Coelho, Alan J
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.03.2001; American Physiological Society
• Subjects: Adult; Anatomy & physiology; Biological and medical sciences; Electromyography; Female; Fundamental and applied biological sciences. Psychology; Gender; Humans; Isometric Contraction - physiology; Knee; Knee Joint; Male; Muscle, Skeletal - physiology; Muscular system; Reference Values; Sex Characteristics; Striated muscle. Tendons; Torque; Vertebrates: osteoarticular system, musculoskeletal system; Knee; Human; Vastus lateralis muscle; Intensity; Rectus lateralis muscle; Sex; Electrophysiology; Lower limb; Striated muscle; Muscle contraction; Quadriceps muscle; Frequency; Electromyography
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2001.90.3.804

1  Human Performance and Fatigue Laboratory, Department of Physical Therapy, and 2  Department of Physical Education, Health, and Recreation, Eastern Washington University, Cheney, Washington 99004 The purpose of this study was to assess the effects of contraction intensity, gender, and muscle on median frequency of the three superficial portions of the quadriceps femoris muscle. Thirty healthy volunteers were assessed for isometric electromyogram activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles with the knee at 60° flexion. Subjects performed 5-s isometric contractions at 10, 20, 30, 40, 50, 60,   70, 80, and 90% of the average of three maximal voluntary contractions. Median frequency ( f med ) of the three muscles was assessed through a power spectral analysis performed over 11 consecutive 512-ms epochs overlapping each other by one-half their length. The f med for each of the 11 epochs was then determined, followed by calculation of the mean and SD. The major findings of this study demonstrated that overall f med was significantly highest for the VL and lowest for the VM, whereas RF f med was between that of the other two muscles. Similar findings were observed for f med variability as the VL was significantly higher than the VM and RF, with no gender differences or differences between the latter two muscles. The results demonstrate that the largest change in f med as a function of contraction intensity occurred for the VL in men (18.6%) and women (7.6%). These findings suggest that muscle fiber-type homogeneity may exist in the VM and RF, which displayed negligible changes in f med , whereas the VL may possess greater morphological variability. vastus medialis; vastus lateralis; rectus femoris; electromyography