Changes in Thickness Versus Shear Modulus in Ultrasound Lateral Abdominal Muscle Measurements During Isometric Contraction: A Case Report

Abstract

There have been no studies in which the change in lateral abdominal muscle thickness was compared with shear modulus and electromyography during isometric contraction. Thus, the aim of this study was to compare the change in external oblique muscle (EO) thickness in relation to shear modulus and electromyography during isometric contraction. The case report was conducted on a healthy man, 46 years of age, without any low back pain symptoms within two years prior to the study. An Aixplorer ultrasound was used in SSI mode to measure muscle thickness and shear modulus in the EO on the right side of the body. The eMotion EMG system was used to control EO muscle activity. The expected force (0 kg, 4 kg, 6 kg, 7 kg) was controlled by a force gauge coupled with an external S-Type load cell. Relative to EO rest thickness during an isometric contraction, EO muscle thickness decreased for each force used. Compared to the rest stage (0 N), the EO shear modulus during an isometric contraction systematically increased, which suggested diminished elasticity during the generation of more force. Similarly, EO activity for Chanel 1 and 2 increased during isometric contraction. Changes in the thickness of the lateral abdominal muscles using ultrasound imaging should not be equated with a change in their function or force generation ability.