[Instrumental studies in laboratories dedicated to the examination of disk overload in health workers]

The main factors to be considered when applying movement analysis techniques to complex situations are analysed. In particular, when the mechanical interactions of the operator with an object to be handled are not easily measurable, as in the case of lifting a patient in a nursery, an approach in which the ground reaction forces are measured through a force platform is more convenient. In these situations the posture and the movement of the subject, that are also difficult to track, do not need to be analysed. The only information needed is the position and orientation of the intervertebral disk and some estimation of the anthropometric parameters of the part of the body which is below the vertebral level of interest. This can be achieved by a relatively simple approach and a few reasonable assumptions. In addition, the method can enable us to analyse forces and moments in 3-D. The results presented refer to several kinds of operations that are usually performed with hospital patients. They include bed to wheelchair transfer, assistance with standing up from a chair, repositioning the patient in bed. It is shown that the compression loads (1810 N to 5110 N) are comparable to those already reported in the literature. In addition, the transversal components (anterior (260 N-707 N) and lateral (5 N-200 N) shear) are of considerable interest. It is also shown how the use of appropriate ergonomical devices to help patient lifting and handling can considerably reduce the loads on the spine: in fact the compression loads are between 991 N and 1644 N.