Although epidemiological studies have been beneficial in identifying the prevalence of musculoskeletal
disorders, the demographics and job types most affected, and types of injuries most sustained, they
do not address the soft-tissue injury mechanisms that result in pain, injury, and impaired function.
This chapter briefly reviews the relevant and related research in soft-tissue pathomechanics of muscle.
Pathomechanics is defined generally as the study of the mechanisms of soft-tissue injury that result
from physical loading exposures. The study of muscle pathomechanics focuses on the effects of both
short-and long-term static and dynamic muscle contractions intrinsic during physical loading on the
functional and cellular changes that lead to injury, pain, and loss of function. Because the internal
and external forces involved in any work-related activity act on multiple structures and tissues in the
body, multiple systems often are affected. Injury, pain, and loss of function may involve damage to
bone, and to soft tissues in the body, such as cartilage, tendon, ligaments, muscle, nerve, or the vascu-
lature. Because the pathomechanics of these tissues may involve different mechanisms that often are
studied independently, separate treatments are warranted. This review will focus specifically on the
pathomechanics of contraction-induced muscle injury.