Sensors for the quantitative analysis of swimmer movements.

The biomechanics of swimming and aquatic activities remained poorly explored due to technical problems of motion capture in water. This project was developed to analyze quantitatively the movement of front-crawl and breast stroke swimming in order to provide the coaches with tools to improve the trainings. Indeed, 3 Physilog® were placed on both forearms and sacrum of a well-trained swimmer, in waterproof boxes in a swimsuit. The signals were recorded during 300m of swimming in an Olympic pool. Analysis of this data with specific swimming algorithms provides measurement of several parameters such as speed, acceleration, push and turn phases of each segment (both forearms and sacrum). Based on a biomechanics model of the swimming activity, pertinent metrics related to performance, arms coordination and energy expenditure were derived from these basic data. The validity of this novel approach was confirmed for this particular activity by comparison against a video-based system (two underwater video cameras in side and frontal views). The Physilog® system offers a reliable, automatic, easy-to-use system with timely feedback for the study of swimming.