Soft-Tissue Pathomechanics - Fundamentals and Assessment Tools for Occupational Ergonomics - page 341

15
Soft-Tissue
Pathomechanics

15.1 Soft-Tissue Pathomechanics .................. 15-1

15.2 Skeletal Muscle Physiology ................... 15-2

Muscle Physiology and Anatomy † Cellular Processes
Initiating Muscle Contractions † Force Generation and
Transmission in Skeletal Muscle † Types of Muscle
Contractions † Musculotendon Actuator

15.3 Contraction-Induced Injury Models ............ 15-8

Human Studies † Animal Models of Muscle Performance and
Injury

15.4 Injury Mechanisms . . . ...................... 15-13

Acute Muscle Injury † Eccentric Muscle Actions in Acute
Myofiber Injury † Factors Affecting Acute Muscle Injury

15.5 Cellular Biology of Muscle Damage ............ 15-22

Strain Injuries and Skeletal Muscle † Physical Damage to
Tissue † Intracellular Ca 2þ and Muscle Damage † Muscle
Inflammation † Muscle Regeneration and Repair † Muscle
Injuries Associated with Low-Force Repetitive Tasks † Long-
Term Changes in Muscle in Response to Injuries † Biomarkers
of Injury

Robert G. Cutlip
NIOSH Health Effects
Laboratory Division

15.6 Recommendations for Future Work ............ 15-27

The Need for More Refined In Vivo Models † The Need for
Tissue Mechanobiology Studies † Summary

15.1 Soft-Tissue Pathomechanics

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

15-1