Design and construction of a 3D force plate prototype for developing an instrumented swimming start block

Force plates have been used in human movement analysis to measure ground reaction forces, centre of pressure (COP) and derived kinetic quantities. In competitive swimming external tridimensional (3D) forces assessment is crucial to improve starting technique performance. This work aimed to describe the design and construction of a 3D force plate prototype, which might be a modular sensor of an instrumented swimming starting block. For this purpose four steps were followed: 1 ) numerical determination of sensor conspicuous spatial positioning; 2 ) development of a first test device and respective calibration procedures; 3 ) final prototype (3D force plate) development and implementation; and 4 ) development and programming of a high speed multiple data acquisition system. Vertical force (< 140 N ± 5%) and COP real time determination (± 3% to centre distance uncertainty) are compliant with the literature data and horizontal force is assessed based on COP displacement time derivatives. The software for data acquisition and interpretation was developed, leading to calibration procedure that provides a set of gains for sequential balance protocol and final transfer matrix. Although the final prototype implementation was the main concern of the current study, its development also has proven to be an important milestone for a dynamometric swimming start block advance.