Developing Skills

Abstract

The purpose of our investigation was to develop and evaluate a device that is able to measure the horizontal acceleration of a swimmer's surface point (here the lumbar vertebral spine). The system we have developed measures the acceleration along the longitudinal- and sagittal-axis and its own inclination towards the horizontal plain. The system is connected to a video system (two analogue cameras) that simultaneously record the swimmer's action. After the measurement, both data are synchronised with a precision of better than ± 1 picture (at 25 fps). In a case study we made measurements for all complete and partial movement actions. The assignment for breaststroke and butterfly is part of this paper. The analysis of acceleration-time- curves allows for a much more direct investigation of the propulsion effects of movement actions than the analysis of velocity-time-curvcs. This is because the maximum of the acceleration occurs during the maximum of propulsion (deceleration) whereas the maximum (minimum) velocity occurs later.