Comparison of the iemg activity elicited during an isometric contraction using manual resistance and mechanical resistance

Abstract

Introduction: Quantification of muscle strength is an essential component of assessment and treatment in rehabilitation. Considering the measurement of the muscle strength, mostly two methods are used. They are qualitative and quantitative measures. Maximum voluntary isometric contraction (MVIC), measured using dynamometer and manual muscle testing (MMT) are the most common measurement techniques used in the clinical and research setting. Objectives: This study's aim was to observe, if greater activity is produced using mechanical instruments for torque measurements (since the resistance is adjusted to subject's maximum capacity) or if tests, position of MMT, and resistance offered by trained physiotherapist are effective. We compared the IEMG (Integrated electromyography) output between manual and mechanical testing during maximal voluntary isometric contraction. Subjects and Methods: Forty normal healthy subjects including 20 males and 20 females were selected for the study. The measuring system comprises an EMG (Noraxon USA, INC, Scottsdale, Arizona) and ®HUR 5340 (Kokkola, Finland) leg extension/curl computer controlled machine for isometric evaluating peak torque. MVIC of the Vastus medialis oblique (VMO), Vastus lateralis (VL), Rectus femoris (RF), Semitendinosis (ST) and Biceps Femoris (BF) were measured from dominant leg using SEMG and then subjects were seated on HUR with hip flexed and chest, pelvis, thigh stabilized. The axis of rotation of HUR aligned with the joint axis and moment arm is fixed for every subject. Each subject performed maximal contraction of 10sec at 60°of test angle to get the peak torque and myoelectrical activity are also recorded while performing the same. Result: Paired t-test analysis were used to see the difference between MMT and HUR IEMG amplitude and the results show significance difference(p< .05) for each muscle when comparing between the EMG amplitude between MMT and HUR. Conclusion: HUR system has very good reliability in measuring muscle strength of the knee extensors and flexors as compared to the MMT, suggesting that it will be useful in clinical applications, especially for professional athletes or physically powerful populations.