Sutherland, Alan D (2022) Biomechanical Assessment of Pitch Length Control and Kinematic Variability in Cricket Fast Bowling. Research Master thesis, Victoria University.

Abstract

Cricket fast bowling coaches have an abundance of knowledge related to speed production and bowling technique. However, bowling coaches find large gaps of research knowledge related to bowling accuracy. While a consistent pitch length (accuracy) can be achieved from a redundant combination of four ball projection parameters (horizontal velocity, vertical velocity, horizontal position, and vertical position), there is no current research of these relationships. Furthermore, the link between body position and ball projection is unknown. While gait studies have employed kinematic effector units to explain functional biomechanics and control of stance and swing limbs of walking, this type of analysis is rare in sports biomechanics. This motivated this study to divide the whole-body into three effector units (Leg, Trunk and Arm) to analyse how body position effects bowling accuracy. This study aimed to provide preliminary information related to the research gap of the general nature of three-dimensional body position variability and bowling accuracy through investigating pitch length control. A group of 12 sub-elite male fast bowlers volunteered to be biomechanically tested on their performance of 18 good length bowling trials. Ball and body kinematics were captured from a threedimensional motion analysis capture system (250 Hz) setup at an indoor cricket pitch. Each bowler’s set of BR and body effector variables were represented as mean and standard deviation from 18 trials. Ball pitch length was determined via a flight prediction model based on constant acceleration. A multi-linear regression analysis showed that the four release parameters accounted for 79% of pitch length variability, where vertical velocity variability accounted for the greatest variability (90%). A coordinated covariance test did not find any redundant cooperation among the four BR parameters. Therefore, pitch length accuracy appears to be achieved by independent control of vertical velocity. Three-dimensional body effector position vectors were time-normalised to the acceleration phase of bowling (FFC to BR) and presented in each dimension as time-waveform signals. The average variance of the effector profile during the bowling phase was calculated across each bowler’s 18 trials and 11 time-slices. A stepwise linear regression analysis found that variance in Leg-X and Trunk-Z effectors can explain 85% of the variance in vertical velocity variability at BR. A coordination covariance test also revealed that redundant coordination of body effector position exists in the X- and Z-dimension. In summary, the ball vertical velocity at BR is the critical parameter that determines pitch length control, while dimension-relevant variability of the Leg effector and Trunk effector determine vertical velocity variability. In summary, this project identified valuable preliminary information that can readily be translated and applied to coaching methods for bowling accuracy. Furthermore, it offers sound insights for future research to enquire deeper into the nature of fast bowling accuracy.

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