Wearable Technology

Document Type



The aim of this study was to evaluate the sensitivity of a phase-based performance assessment method obtained from a sacrum IMU to assess swimming progress. Five IMU-based goal metrics were extracted from the literature for the main swimming phases of wall push-off, glide, strokes preparation, swim, and total lap. Sixteen young competitive swimmers completed five one-way front crawl laps at maximum speed with an IMU attached to the sacrum while the coach recorded lap time as the main indicator of performance level. To monitor the swimmers' performance improvement, the same test was repeated once a week for 10 weeks. The minimum 0.5s change in lap time was calculated as the minimum worthwhile enhancement. The results showed that the goal metric of whole lap and swim phase closely predict swimming progress (e.g., accuracy, precision, sensitivity, and specificity of 0.91, 0.89, 0.94, and 0.95 for the whole lap goal metric, respectively). Other goal metrics achieved high precision and specificity (≥ 0.79) for detecting the progress, indicating that they can be reliably used for further improvement of swimmers in the level of swimming phases. The results showed that coaches can use the goal metrics in training sessions to track the progress of the swimmers in each phase.