Intra-session and inter-session reliability of electromyography in leg extension during maximum voluntary isometric contractions of quadriceps: The effect of knee angle

Abstract

Numerous factors can influence the reliability of the signal obtained by electromyography EMG among which the type of contraction is practically fundamental. This study aimed to investigate intra-and inter-session reliability of EMG for maximal voluntary isometric contraction (MVIC) of the knee extensors at different joint angles. Nine healthy male students from the Faculty of Sport and Physical Education voluntarily joined the experiment. Main characteristics of the subjects were: age 23±1 years, body weight 80.8±7.8 kg and body height 182±7 cm. EMG signal from three surface heads of quadriceps femoris was recorded -vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF). Subjects had to perform 3 MVIC as fast as possible, as strong as possible at 6 different knee joint angles on 2 occasions separated by 7-8 days. The intra-class coefficient of correlation (ICC) was used to identify relative intra-and inter-session reliability, while standard error of measurement (SEM) was used to calculate the absolute reliability of each tested muscle. All muscles showed high intra-session reliability (ICC=0.488-0.988 and SEM=1.38-11.35). VL showed good inter-session reliability for most of the conditions (ICC=0.603-0.948), VM for two knee angles (ICC120°=0.764 and ICC130°=0.788), RF was not reliable for any knee angle. This study indicates that RF does not need to be used in EMG testing in leg extension MVIC due to lack of reliability between two sessions, and If EMG RMS from VL and VM will be tested, knee angle of 120° should be used for the testing.

Effects of Knee Extension Joint Angle on Quadriceps Femoris Muscle Activation and Exerted Torque in Maximal Voluntary Isometric Contraction

“…The testing procedure was conducted following previously reported procedures that were shown to be reliable [ 31 , 32 ]. All participants took part in a 10-min warm-up protocol consisting of five minutes on a bicycle ergometer and five minutes of dynamic stretching.…”

“…The EMG signal from VL and VM of the quadriceps femoris was recorded using an eight-channel single differential surface EMG sensor (Delsys Inc., Boston, MA). Electrodes were placed according to the previously reported procedure [ 31 , 33 ]. In short, the skin was shaved at the location of the electrode placement, cleaned with alcohol, and lubricated with ultrasound gel for better electrical conductivity.…”