Microtechnology for measuring intra-stroke arm and leg timing in swimming
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Introduction: The measurement of technique for an athlete has traditionally been performed in the laboratory where the required instrumentation is available and environmental conditions can be easily controlled. In this environment, dynamic characteristics of athletes are assessed using treadmills, rowing and cycling machines and even flumes and tethers for swimmers. In general these machines allow for the monitoring of athletes using instrumentation that cannot be used in the training environment, but instead requires the athlete to remain quasi-static, thus enabling a constant field of view for optical devices and relatively constant proximity for tethered electronic sensors, breath gas analysis etc. The use of accelerometers to measure activity levels for sporting, health and gait analysis is emerging as a popular method of biomechanical quantification of health and sporting activity. Detailed analyses of the fine structure of movements reveal critical performance characteristics, which potentially can shave milliseconds from lap times. The objective of this research was to measure the intra-stroke movement patterns for elite swimmers, specifically the timing of arm-stroke and leg-kick and provide new information to QAS swimming coaches on as the athletes are freely swimming in training and/or race simulation conditions. Methodology: The reliability and validity of the micro-technology was quantified via graduated comparative analysis of the inertial sensor outputs relative to a recognized benchmark. Using a National Sports Science Quality Assurance motion analysis laboratory and Qualisysix camera 500Hz three dimensional motion analysis system a simple, single plane movement task of flexion/extension of the knee joint was measured and compared for validity and reliability. The calibrated inertial sensors were placed on the hand, head, sacrum, and ankle of the swimmer prior to entering the water. The data collection was synchronised on the sensors via a radio frequency and the swimmers completed 100 m freestyle swimming. Results and conclusions: This new monitoring system provides currently unknown feedback on the intra-stroke timing mechanics for swimmers, which is a fundamental factor in enhancing performance. Specifically the timing of the pull and recovery phase in relationship to the kick are identified in free swimming. From this benchmark variations in the pattern of intra-stroke timing due to fatigue or change in velocity can be identified. This critical and real-time information can led in substantial changes in training techniques of the coaches and athletes.
Journal of Science and Medicine in Sport