The accuracy of physiological work studies depends only in part on the measuring instrument itself. If the measurement is performed on work which is insufficiently described, the total accuracy of the measurement is decreased. A proper selection of description variables increases the accuracy of physiological work measurement and makes a fairly general prediction of the energy expenditure possible. A model for prediction of energy expenditure from physical data is proposed and has been tested in a number of industrial cases. The accuracy of the result is of the same order of magnitude as a good work study.