THE EFFECT OF A GAME-SPECIFIC SHORT TERM FATIGUE PROTOCOL ONKICKING IN AUSTRALIAN FOOTBALL

The purpose of this study was to three dimentionally evaluate the effects of a short term game specific fatigue protocol on the kinetics of elite and sub-elite Australian Footballers (AF) during a drop punt kick. Five AF players performed kicks pre and post fatigue protocol. Three dimensional data of the pelvis and kick leg was obtained using a three tower optotrak Certus system (200Hz) and joint torques and moments were calculated in Visual 3D from kick foot toe off until ball contact. Sprint time indicated the protocol induced fatigue. Hip flexion torque significantly increased following fatigue indicating a change in movement strategy similar to that found for jump landing. This greater hip reliant post-fatigue kicking strategy has implications for both skill enhancement and injury prevention

Biomechanical Considerations of the Effect of Fatigue on Kicking in Australian Rules Football

The punt kick is a fundamental skill used in team sports, including Australian Football. Australian football is a physically demanding sport played for long durations on large grounds with regular bursts of high intensity running. While these game conditions might be expected to elicit large amounts of fatigue, there has been little work examining how kick technique might change under the effects of fatigue. Importantly, changes in fatigued kicking technique have been found in soccer so it might be expected that changes will exist in the punt kick as well. The purpose of this thesis was to evaluate the effects of short and long-term fatigue on punt kicking kinematics and kinetics using elite and junior Australian Football players. Three-dimensional motion capture systems tracked maximal distance kicks from toe-off to ball contact before and during match-specific fatigue protocols. In the short-term fatigue study (Study 1), elite Australian Football players were able to maintain foot speed (performance) during fatigued kicks by increasing segmental ranges of motion and velocities, particularly at the thigh. Participants were able to make changes to their punt kicking technique in order to maintain performance after short high-intensity bursts of activity. In the longer-term fatigue studies (Study 2 and Study 3), junior Australian Football players initially displayed a decrease in foot speed, due to a decrease in knee extension moment. However, this decrease in performance appeared to be minimised through increasing velocity and angles higher up the chain at the thigh and hip. During initial stages of long-term lower intensity activity, performance decreased and participants made technique changes in an attempt to limit this decrease. Performance then improved later in the long-term protocol due to the kicking thigh widening its frontal plane angle and flexing more at the hip. Overall, fatigue caused changes to punt kicking technique

Analysis of the radiation flux profile along a PV trough concentrator

ABSTRACT: The primary advantage of a PV concentrator is that concentrating light allows a significant reduction in the area of solar cell coverage, the main cost driver in a flat plate system. PV systems, whether flat plate or concentrating, normally have groups of solar cells connected in series in order to increase voltage and limit current. However, low illumination on a single cell proportionally reduces its current, and hence affects the performance of all other cells in series. Ideally, a reflective PV concentrator system will have high concentration, a uniform flux distribution, and low cost. However, it is difficult to obtain these three conditions simultaneously, as cost tends to increase with better mirror quality, improved tracking accuracy, and the use of secondary flux modifiers. Linear concentrators have the advantage of simpler and cheaper tracking and support structures than dishes; however, achieving a consistent flux profile on every cell along the focal line is challenging. The aim of this paper is to present results of direct measurements of the flux profile along the length of a single axis tracking trough, and to develop simulation techniques that allow the reasons for peaks and troughs in the flux profile to be better understood

The effect of a game-specific short term fatigue protocol on kicking in Australian Football

The purpose of this study was to three dimentionally evaluate the effects of a short term game specific fatigue protocol on the kinetics of elite and sub-elite Australian Footballers (AF) during a drop punt kick. Five AF players performed kicks pre and post fatigue protocol. Three dimensional data of the pelvis and kick leg was obtained using a three tower optotrak Certus system (200Hz) and joint torques and moments were calculated in Visual 3D from kick foot toe off until ball contact. Sprint time indicated the protocol induced fatigue. Hip flexion torque significantly increased following fatigue indicating a change in movement strategy similar to that found for jump landing. This greater hip reliant post-fatigue kicking strategy has implications for both skill enhancement and injury prevention