The effect of digitisation of the humeral epicondyles on quantifying elbow kinematics during cricket bowling

In the sport of cricket the objective of the "no-ball" law is to allow no performance advantage through elbow extension during ball delivery. However, recently it has been shown that even bowlers with actions that are considered within the law show some elbow extension. The objective of this study was to investigate: [1] the effect of elbow orientation during anatomical landmark digitisation and [2] the choice of upper arm tracking cluster on the measurement of elbow angles during cricket bowling. We compared the mean elbow angles for four different elbow postures; with the joint flexed at approximately 130°, 90°, in full extension and with the elbow flexed with the humerus internally rotated, and two upper arm clusters in two different situations: [1] during a controlled movement of pure flexion-extension and [2] during cricket bowling. The digitised postures of the anatomical landmarks where the elbow was extended and at 90° of flexion were more repeatable than the other two postures. The recommendation of this study when analysing cricket bowling is to digitise the humeral epicondyles with the joint flexed at 90°, or in full extension, and to relate their positions to an upper arm cluster fixed close to the elbow.