ABSTRACT
Physical, psychological and behavioral resources are not a fixed and stable set of individual characteristics but change over time and are influenced by capacity, motivation, stress responses and the demands of the working conditions. For instance, these resources may increase because of on-the-job training or the availability of powered assistance machinery. In the repetitive lifting example the introduction of equipment to do the lifting will reduce the energy requirements and the local muscle fatigue, while training in proper lifting techniques may also reduce these same outcomes. Stress responses can influence the biological and psychological resources available to an individual. Individual personality characteristics, genetic make-up and health status all influence the physical resources available to the individual and the nature of the stress responses.
