WATER POLO PENALTY SHOT TRAJECTORY MODEL

Context: Using MATLAB software to investigate interactions of bio-kinetic chain movements of elite water-polo athletes to determine resultant trajectory and reaction-time in a 5m penalty shot during competitive play.

Aims: Current research shows launch velocity of a short-range water-polo shot is highly dependent on anatomical twist and extension angle of kinetic-chain members such as the torso and upper-arm respectively. 

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Invented in the 19th Century, water-polo has evolved into a power and endurance-based sport that combines techniques found in sports such as baseball, rugby and football. Points are earned by throwing the ball into the opposing goal during normal play as well as earned penalty shots, as seen in football. The fastest recorded penalty shot is 26.8 ms−1 by a Turkish national team male; 5.7 ms−1 faster than the average elite male water-polo player (Solum, 2017). This equates to 0.186 s for the defending goalie to react and stop the ball. As the average reaction time (RT) of an elite water-polo male is 0.213s (Gardasevic et al.,2019) this would require preemptive perception and leave little time for a successful defensive play.

Numerous studies have supported the positive relationship between certain components of a shooter’s technique and launch velocity (Razak et al., 2018). Solum (2017) quantified the torso as producing 25% of the total force in ball launch velocity. Melchiorri et al. (2011) suggested a positive relationship to trunk rotation time and ball velocity through a study of the Italian men’s National team. These studies support the findings of Feltner & Nelson (1996) who used direct linear transformation (DLT) via planar images to quantify the contributions of anatomical kinetic chains towards the ball release velocity. It was determined the key contributing factors were the trunk twist (24.2%), rotation of the upper arm (13.2%), forearm extension (26.6%), and the relative velocity of the ball to center of hand (10.4%), totaling 75% of all velocity contributions from 14 observed components. These findings were adapted to formulate a numerical model that receives user input for initial launch conditions to plot a trajectory, and subsequently calculate total time per penalty shot, otherwise referred to as RT. This information may provide insightful intelligence to aid water-polo players and coaches in determining strategic trajectories and appropriate training techniques.

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