Muscle strain injury vs muscle damage: Two mutually exclusive clinical entities

Muscle strain injury and exercise-induced muscle damage have been described as a continuum of injury whereby microtears (muscle damage) lead to muscle strain injury. However, the clinical scenario is one of two mutually exclusive conditions that differ markedly in terms of site of injury, mechanism of injury, associated symptoms, repair process, and re-injury rate. Muscle strain injury is a tearing of muscle fibers close to the muscle-tendon junction during the application of a single tensile load, with sudden debilitating symptoms, and a subsequent repair process that is slow, and often incomplete, resulting in a high risk of recurrence. Exercise-induced muscle damage is a disruption to myofibrils that occurs gradually during eccentrically biased exercise, resulting in delayed symptoms, that typically resolve uneventfully, with a repair process that makes the muscle resistant to a recurrence of damage. Thus, muscle strain injury and exercise-induced muscle damage should be viewed as mutually exclusive clinical entities.