The most important part of a swimming stroke occurs underwater where propulsion is accomplished. This means that the coach or teacher concerned with evaluating the stroke mechanics of swimmers must have a clear picture of the underwater action. Therefore, a watertight plexiglass box was developed which allows video recording of stroke technique below the surface of the water. Conventional filming through an underwater camera is expensive and one must wait for the film to be developed in order to see the result. It also requires trained photographers, which most coaches and teachers are not. Dal Monte (1971) described a sophisticated apparatus allowing cinematographic recordings perpendicular at all times to the swimmers' movements and at a speed identical to that of the swimmers' displacements in the water. Mcintyre and Hay (1975) solved the observation problem with the development of an inverse periscope. Although we don't want to criticize this method, we think the method described by Hoffman (1976), which was used as the basis for the development of our watertight plexiglass box, is a more economical and less time-consuming approach to observing and evaluating underwater movements. It is the purpose of this article to provide a description of a device that is easy to build in a technical laboratory at low cost. In addition, it is portable and therefore can be used in any pool. Furthermore, trained individuals are not needed to obtain clear and usable video pictures.
© Copyright 1983 Biomechanics and Medicine in Swimming. Veröffentlicht von Human Kinetics. Alle Rechte vorbehalten.