ABSTRACT
Physiological load of occupational physical work can be assessed on the basis of a rate of energy expenditure or oxygen consumption by the body. In many industrial tasks, it is also important to determine
how much force must be generated by muscles to lift or support the weight of objects or to maintain the steady body position. However, these data are unsatisfactory when individual work tolerance has to be predicted. For this purpose, it is necessary to establish a relationship between the oxygen requirement for a given job to the individual maximal oxygen uptake or relation of force required to perform any task to the individual muscle strength (maximal voluntary contraction force). Moreover, many additional factors in the working environment, such as high or low ambient temperature, noise, etc., or psychological stress can influence work tolerance. Thus, the assessment of strain imposed by work and accompanying environmental factors should also include direct evaluation of the body responses to the work load or exposure to specific factors. Among them are indices of cardiovascular and respiratory system function, changes in body temperature, rate of sweating, muscle strength, muscle electrical activity (EMG), or indices of fatigue on the central nervous system such as disturbances in movement coordination, lowered level of arousal, etc.
