Manual materials handling (MMH) account for approximately $15.0 billion of injuries cost in the United States alone. Because of the need to establish manual handling guidelines, different approaches to achieve this goal were pursued. Such approaches are based on biomechanics, work physiology, and psychophysics. In order to better understand the MMH system's behavior, models were developed. These models can be divided into biomechanical models, physiological models, psychophysically based capacity models, safe load handling models, and simulation models. This paper will present a sample of these models and discusses their advantages and disadvantages.