The relationship between foot-ball impact and flight characteristics in punt kicking

Abstract

In football kicking, a player imparts the initial flight characteristics by impacting the ball with his foot. Imparting the correct combination of flight characteristics is the basis of a successful kick. However, examination of the relationship between foot-ball impact and flight characteristics for a non-spherical ball, the ball shape in Australian football and rugby, has been limited to ball velocity. Consequently, little is known of the relationship with other flight characteristics of ball trajectory and spin. The aim of this study was to determine the relationship between impact and initial ball flight characteristics. A mechanical limb, designed to replicate the impact phase of Australian football, performed punt kicks. Four impact characteristics were systematically examined to determine their influence on flight characteristics: foot velocity, medial–lateral impact location, proximal–distal impact location and ball orientation. This study identified each flight characteristic (ball velocity, elevation angle, azimuth angle and spin rate) were influenced by multiple impact characteristics (foot velocity, ball orientation and/or impact location). For example, elevation angle was increased by foot velocity, relative foot-ball orientation and proximal–distal impact location on the foot. Foot velocity had the largest influence on ball velocity (linear slope = 1.43). Medial–lateral impact location had the largest influence on azimuth angle (linear slope = 2.73). Ball orientation had the largest influence on elevation angle and back-spin rate, both measures were sine dependent (elevation angle curve amplitude = 19.4°; back-spin rate curve amplitude = 2754°/s). Players must control all impact characteristics to successfully kick to their desired destination.