ABSTRACT
Spin bowling deliveries in cricket, finger spin and wrist spin, are usually (Type 1, T1) performed with forearm supination and pronation, respectively, but can also be executed with opposite movements (Type 2, T2), specifically forearm pronation and supination, respectively. The aim of this study is to identify the differences between T1 and T2 using an advanced smart cricket ball, as well as to assess the dynamics of T1 and T2. With the hand aligned to the ball's coordinate system, the angular velocity vector, specifically the x-, y- and z-components of its unit vector and its yaw and pitch angles, were used to identify time windows where T1 and T2 deliveries were clearly separated. Such a window was found 0.44 s before the peak torque, and maximum separation was achieved when plotting the y-component against the z-component of the unit vector, or the yaw angle against the pitch angle. In terms of physical performance, T1 deliveries are easier to bowl than T2; in terms of skill performance, wrist spin deliveries are easier to bowl than finger spin. Because the smart ball allows differentiation between T1 and T2 deliveries, it is an ideal tool for talent identification and improving performance through more efficient training.
ABSTRACT
Background: In previous studies that analyzed the biomechanics of spin bowling with a smart cricket ball, it was evident that not all the torque applied to the ball was converted into spin rate, with varying losses among different bowlers. This study aims to investigate the factors contributing to these losses. Methods: Developed in 2011, the world's first intelligent cricket ball features five physical and five skill performance parameters. Our study correlates five skill parameters with the ratio of total torque to spin rate to determine the most influential skill parameter. Results: The parameter that most affected the conversion of torque to spin rate was the ratio of maximum angular acceleration to maximum angular velocity. Since the unit of the latter ratio is measured in s-1 or Hz, we hypothesized that the duration of a time-window in which the torque is generated could be a factor in determining the effectiveness of torque to spin conversion. Upon closer examination of the data, we discovered that the spin torque (the torque component that boosts the spin rate) generated earlier in relation to the release point led to greater conversion of total torque into spin rate. Paradoxically, this occurred at smaller peak spin torques. As the time-window of the spin torque widens despite its decreasing magnitude, the angular impulse increases. Conclusions: As the skill parameter calculated from the ratio of maximum angular acceleration to maximum angular velocity correlates well with the time-window during which torque is generated, it can serve as a good indicator of skillful torque to spin conversion, and a potential parameter for talent identification.
ABSTRACT
INTRODUCTION: Profiling of cricket bowlers is performed with motion analyses systems that require the placement of markers on the bowler's body and on the ball. Conventional smart balls such as cricket and baseballs provide only one speed and one spin rate datum at the release point, which is insufficient for biomechanical profiling. METHOD: In this study, we used an advanced smart cricket ball that measures the angular velocity at 815 Hz and calculates four further physical performance parameters (resultant torque, spin torque, power and angular acceleration) and five new skill parameters (precession, normalised precession, precession torque, efficiency and ratio of angular acceleration to spin rate), which we used for profiling and talent identification of spin bowlers. RESULTS: The results showed that the spin rate is a function of physical (torque) and skill proficiency, namely how efficiently the torque is converted to angular velocity rather than being wasted for precession. The kind of delivery also influences the efficiency, as finger-spin deliveries were less efficient than wrist-spin ones by 6.8% on average; and topspin deliveries were generally more efficient than backspin ones by 15% on average. We tested three bowlers in terms of physical and skill performance during a 10-over spell, revealing that some parameters can improve or decline. When profiling a topspinner, we detected from the performance parameters a lower skill performance than expected, because there was an initial arm motion for backspin delivery before releasing the ball with a topspin. After training intervention, the skill parameters improved significantly (the efficiency increased from 39% to 59%). CONCLUSIONS: The advanced smart cricket ball is a classic example of mobile computing for sport performance analysis that can conducted indoors as well as outdoors, generating instant data from 10 performance parameters that provide critical feedback to the coach and bowler.
