Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications.

Abstract in brief

• Eccentric exercise involves lengthening the muscle while contracting, which can cause muscle damage, soreness, and stiffness in untrained individuals due to damage to muscle fibers.
• The initial damage may result from harm to the excitation-contraction system or disruption of sarcomeres, leading to decreased active tension, altered muscle length, and increased passive tension, indicating sarcomere disruption.
• Repeated eccentric exercise leads to adaptation, likely by increasing the number of sarcomeres, which shifts the muscle's optimal tension length and reduces damage, suggesting potential clinical uses like injury prevention through controlled eccentric training.