Reference: N Davey D James, Swimming Intra-stroke Metric Identification Using Wrist Mounted Inertial Sensors, Journal of Science and Medicine in Sport 12, S31-S31
Abstract: Introduction: In swimming the analysis and metrics of a stroke require the stroke observation in real time or on video, with subsequent interpretation and feedback. Using synchronised inertial sensors attached to the swimmers wrists movement patterns can be recorded. The inertial sensor data can be used in the analysis of stroke metrics. Prior work with body mounted inertial sensors for stroke type identification is extended to consider stroke and intra-stroke relationships. Methodology: A dry land experiment was conducted using a Qualysis motion capture system and swimming ergometer in parallel with the inertial sensors to provide reference and validation data. The swimming ergometer measured stroke length and force. The subject performed three sets of freestyle, butterfly and breaststroke at easy, medium and race pace. Results: Analysis of the inertial data shows that stroke timing metrics such as stroke frequency and stroke rate are obtainable when compared to ergometer data. Elements of the intra-stroke phases can also be obtained using the gyroscope data rotation axis defined by the lateral and medial wrist positions. This is validated against the motion capture system. Intra-stroke phases such as pull/propulsion and timing between left and right side can also be obtained. Conclusions: Results indicate that stroke and intra-stroke metrics can be obtained from wrist mounted inertial sensors. This provides an alternate method for obtaining such metrics. As dry land does not replicate in-water conditions, further in-water testing is required to fully validate the results.