Front-Crawl Instantaneous Velocity Estimation Using a Wearable Inertial Measurement Unit

Abstract

Monitoring the performance is a crucial task for elite sports during both training and competition. Velocity is the key parameter of performance in swimming, but swimming performance evaluation remains immature due to the complexities of measurements in water. The purpose of this study is to use a single inertial measurement unit (IMU) to estimate front crawl velocity. Thirty swimmers, equipped with an IMU on the sacrum, each performed four different velocity trials of 25 m in ascending order. A tethered speedometer was used as the velocity measurement reference. Deployment of biomechanical constraints of front crawl locomotion and change detection framework on acceleration signal paved the way for a drift-free integration of forward acceleration using IMU to estimate the swimmers velocity. A difference of 0.6 ± 5.4 cm·s−1 on mean cycle velocity and an RMS difference of 11.3 cm·s−1 in instantaneous velocity estimation were observed between IMU and the reference. The most important contribution of the study is a new practical tool for objective evaluation of swimming performance. A single body-worn IMU provides timely feedback for coaches and sport scientists without any complicated setup or restraining the swimmer's natural technique.

Magnetic Field Swimmer Positioning

“…Table III shows descriptive statistics relating to this improvement. This improvement is in contrast to inertial sensor based systems, which whilst they can be accurate at the beginning of a length, due to drift caused by noise in the sensors become increasingly poor over time [13]. For this reason, inertial positioning systems for swimming cannot be real-time and need to apply correction algorithms to the inertial data at the end of a length when the swimmer is at a known position.…”

“…A Google Nexus 4 smartphone is placed in a waterproof pouch and strapped tightly onto the central lower back of the swimmer using a simple waist strap and pouch. This position was chosen, as in previous IMU research [1], [3], [5], [13], [14] because it offers a predictable orientation relative to the base of the swimming pool, and allows orientation sensing to reliably detect the direction of swimming. Fig.…”

“…It is possible to correct for this once a full length has been swum, and estimate position and velocity [13], [14], but this removes the ability to respond in real-time to a swimmer's movements.…”

Adaptive Fingerprinting in Multi-Sensor Fusion for Accurate Indoor Tracking

“…To tackle these challenges, several considerations are taken: [29], [30]. In tests performed, 1 Second time window provides an optimal trade-off.…”

Design De Wearables Para Uso Esportivo: Sensores Inerciais Aplicados À Natação Em Piscinas

“…Dadashi (2012), desenvolveu algoritmos para a obtenção do perfil de velocidade de um atleta durante um tiro e o perfil de velocidade intra-cíclica para cada braçada. Os dados foram captados por um sensor inercial tri-axial fixado na lombar do atleta, e computados posteriormente informando-se a dimensão da piscina e o tempo cronometrado manualmente da prova, para contornar os erros de integração do sinal.…”