Optical motion analysis systems are typically used to perform kinematic analysis of human movement. However these systems are primarily laboratory-based, expensive, have a limited calibration volume, and often require considerable post processing time. Such an approach to motion analysis is therefore often impractical for analysis of athletes during actual training and performance environments. A strong need exists to develop methods that provide meaningful information about athletic performance in the field without unnecessarily encumbering the athlete or constraining the natural environment. Such information should be rapidly available to the coach and athletes and presented in a form that is practically relevant and easy to interpret. At present the validity and reliability of such methods for evaluating running performance is unknown.
A tri-axial accelerometer based system using dual axis ADXL202 accelerometers was constructed using a Hitachi microprocessor and readily available components. Using a scheduler based operating system sample rates of up to 250 Hz per channel were achieved using the on-board 10-bit ADC. Sampled data was then encoded for transmission on commercially available Bluetooth modules. Up to seven modules can be connected on a single ‘piconet’ network and acquired synchronously (after calibration) to within 5 ms. Receiver client software was developed in Visual Basic allowing for near real-time acquisition and display from a number of accelerometer nodes. Transmission ranges in excess of 100 m allow the system to be used in laboratory and field environments.
We are currently using the device to quantify aspects of elite running performance including ground contact time, impact attenuation, trunk stability and sprint start technique. In the near future we propose to incorporate gyroscopes into the device to provide information about the orientation of the body under dynamic conditions.