Injuries and disorders caused by overexertion and repetitive motion are the leading causes of compensable lost-time cases in the United States. Epidemiological and laboratory-based research methods have been used to evaluate the significance of various risk factors associated with overuse injuries and disorders. The National Institute for Occupational Safety and Health performed a comprehensive review of over 600 epidemiological studies in 1997 and concluded that there was evidence of a causal relationship between low-back injuries and disorders and workplace exposures to forceful exertions, awkward posture, and vibration. Although epidemiological studies provide important insights to understanding the causes of work-related overuse disorders, they are sometimes criticized for their inability to measure precisely how people respond to specific risk factors found in the workplace. This article presents a review of recent laboratory studies and biomechanical models of work factors believed to be associated with increased risk of low-back injuries and disorders. Biomechanical models and laboratory studies do not replace epidemiological studies. However, these approaches provide important complementary information that is needed to understand the complex process of how exposures to physical risk factors result in strain that may ultimately lead to injury or disease. These studies also provide important insights as to how people react and respond to specific physical risk factors found in the workplace. Combined with epidemiological research, laboratory studies are an essential element in understanding the causes and prevention of work-related overexertion injuries.