Static effort, the lower the efficiency. This is particularly true when work is carried out with a bent back. In every kind of heavy work it is important to aim at maximal physiological efficiency , not only to use energy economically but to minimise stresses upon the operator. For this reason work physiologists have made a great many attempts to measure the efficiency of various kinds of working methods and physiological the use of different tools and other equipment. Their results make it possible to formulate guidelines for the layout of work and the design of equipment, which are of particular importance where strenuous work is concerned. Some examples are given in Table 6.3. lling Shovelling is a common form of manual work, which has fur Ar- studied at the Max-Planck-Institut been thoroughly beitsphysiologie in Dortmund, Germany (Lehmann, 1962) and. more recently, at Pennsylvania State University in the USA by Freivalds (1987). Both studies demonstrated that certain tool forms are better suitable than others to perform maximal work with minimal effort. The highest level of efficiency was attained when a load of 8-10 kg was shovelled 12-15 times per minute. In addition to the Table 6.3 Maximum efficiency in various physical tasks Per cent