This research quantified the velocity during the swimming phase and investigated the arm symmetry using a single triaxial accelerometer in freestyle swimming. This included the data collection, analysis and feature extraction of parameters of interest. A main question related to the collection of acceleration data from several athletes in the discipline of swimming under training conditions. This involved developing and testing of suitable sensor technology for tracking the movement of the swimmer. Furthermore, after the first data was collected, more elementary questions evolved: Which data is of interest to athletes and coaches and therefore should be collected? What does the acceleration data mean? How should this data be interpreted? These questions involve human movement studies, especially related to biomechanical & physiological sports science. It also includes digital signal processing of the data. This analysis was performed on a desktop computer after the data were collected from the inertial sensor. This thesis therefore addresses two issues, the data collection and the data analysis used to extract information of interest to athletes and coaches.