Tennis Racket (IMAGE) Friedrich-Schiller-Universitaet Jena Caption Grunting noises in tennis influence the prediction of ball flight. Sport psychologists from Jena University come to this conclusion in a new study. Credit Anne Guenther/University Jena Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.