Ultrasound Elastography of Biceps Brachii in Well-Trained Men Following Eccentric Exercise-Induced Muscle Damage

Recent advancements in supersonic shear wave elastography (SWE) have enabled a non-invasive assessment of muscle stiffness, yet research on the immediate and short-term effects of eccentric exercise-induced muscle damage (EIMD) in well-trained individuals is limited. This study aimed to investigate how eccentric training affects biceps brachii stiffness, muscle soreness, and maximal voluntary isometric contraction (MVIC) in well-trained men. Thirteen male participants underwent baseline assessments, including elastography images, MVIC of the elbow flexors, and muscle soreness measurements. They then performed an eccentric exercise protocol consisting of four sets of ten repetitions on a dynamometer, with repeat elastography and MVIC measurements taken immediately post-exercise and again at 10 minutes, 48 hours, and 96 hours post-intervention. The results showed significant reductions in muscle stiffness, as indicated by shear modulus (µ), immediately and at 10 minutes after exercise. MVIC also demonstrated significant decreases immediately post-exercise and at both the 10-minute and 48-hour marks compared to baseline. Muscle soreness peaked at 48 hours and remained until 96 hours. These findings suggest that the reduction in biceps stiffness and MVIC right after eccentric exercise may be indicative of mechanical stress and sarcomere rupture. The response to EIMD appears to differ in trained individuals compared to untrained individuals, emphasizing the value of elastography as a tool for monitoring acute biomechanical changes following high-intensity exercise.