Andrew James Wixted

Accelerometers: An underutilized resource in sports monitoring

Play based sports monitoring techniques provide coaches and players with the tools to better measure the effects of training or live performance. This paper explores the advantages of using accelerometers units, in an effort to better analyse over ground running in professional athletes. A large portion of studies in player monitoring in the Australian Football League (AFL) utilize GPS to obtain time and distance measurements.

Detection of throwing in cricket using wearable sensors

One of the great controversies of the modern game of cricket is the determination of whether a bowler is using an illegal throw-like bowling action. Changes to the rules of cricket have reduced some of the confusion; yet, because of the complexities of the biomechanics of the arm, it is difficult for an umpire to make a judgement on this issue. Expensive laboratory-based testing has been able to quantify the action of a bowler and this testing is routinely used by cricket authorities to assess a bowling action. Detractors of the method suggest that it is unable to replicate match conditions, has long lead times for assessment and is only available to the elite. After extensive laboratory validation, we present a technology and method for an in-game assessment using a wearable arm sensor for differentiating between a legal bowling action and throwing. The method uses inertial sensors on the upper and lower arms that do not impede the bowling action. Suspect deliveries, as assessed by an expert biomechanist using high-speed video and motion capture, reveal valid distinctive inertial signatures. The technology is an important step in the monitoring of bowling action on-field in near real-time. The technology is suitable for use in competition as well as a training tool for developing athletes.

Low-cost short -range wireless optical FSK modem for swimmers feedback

This paper reports 3 axis accelerometer data transfer over a one meter underwater path at 10 cm depth using a 2400 bps optical wireless frequency shift keying (FSK) at very low frequency (VLF). The modulation frequencies used were 10 and 12 KHz. The prototype modem was designed and implemented for real time feedback for swimmers in the pool. The optical transmitter included an accelerometer unit with a microcontroller, the modulator and a detector circuit based on an integrated detector preamplifier (IDP). The cost of the components for the optical transmitter and receiver was less than AU

Peak outward acceleration and ball release in cricket

25. Range experiments were performed in air and underwater, with and without bubbles. The received data was error free for 1.3 m in air and for more than 1.1 m underwater without bubbles. The underwater range decreased to 70 cm with bubbles. The availability of the link between the wrist and head of a swimmer was approximately 50% and varied with the position of the wrist. This enables stroke rate data to be presented to the swimmer via a goggle mounted display.

Inertial sensor orientation for cricket bowling monitoring

Abstract The purpose of this study was to investigate the utility of peak outward acceleration (POA) measured from an inertial sensor worn at the wrist as an indicator of the critical end point of the bowling action – ball release, a critical element when assessing illegal actions. Twenty-one finger-spin and fast bowlers from nine countries were recruited from the ICC under-19 Cricket World Cup to take part in this research. Bowlers delivered a cross section of their standard deliveries while wearing an inertial sensor placed on their wrists. Ball release was determined by a validated motional analysis ball release (MABR) protocol and compared to the simultaneously collected POA. POA was shown to be highly correlated with MABR (R2 = 0.98) and a Bland–Altman plot indicated that all 148 trials were within the 3.42 frame (0.014 s) limits of agreement. POA when measured by an inertial sensor worn on the wrist during bowling had a close relationship with an established method of identifying ball release in a biomechanical laboratory regardless of bowler and delivery type. Further, accuracy can be achieved with the adoption of a simple regression equation applied to the POA and as such is a valid measure of ball release in cricket bowlers.

Signal processing for estimating energy expenditure of elite athletes using triaxial accelerometers

Inertial sensors are a potential method of measuring the elbow angle during cricket bowling, currently an indicator of illegal bowling. To detect the elbow angle it was necessary to orient sensors relative to the elbow axis. An elbow orientation exercise was developed and the sensor orientation relative to the elbow axis calculated for upper-arm, forearm and wrist mounted sensors for different muscle loading and wrist rotation. Inertial rate-gyroscope outputs were compared for sensors before and after adjustment for elbow-axis orientation. This output was compared to the results obtained from a Vicon motion capture analysis system. Adjusting the sensor orientation based on the output from the orientation exercise improved the correlation between outputs of the upper-arm and forearm sensors but also indicated that the sensors were susceptible to muscle loading and wrist rotation effects that will need to be accounted for in any sensor based illegal bowling detection system.

Measurement of Energy Expenditure in Elite Athletes Using MEMS-Based Triaxial Accelerometers

Fitness development of elite athletes requires an understanding of physiological factors such as athlete energy expenditure (EE). For athletes involved in football at the elite level, it is necessary to understand the energy demands during competition to develop training regimes. By identifying an appropriate EE estimator in triaxial accelerometer data, in conjunction with identifying sources of inter-athlete variance in that estimator, signal processing was developed to extract the estimator. In this system, low-power signal processing was implemented to extract both the EE estimator and other information of physiological and statistical interest