Doctoral Thesis / Dissertation from the year 2021 in the subject Sport - Miscellaneous, grade: PhD, , course: PhD in Health Sciences, language: English, abstract: Shoulder motion is considered one of the most stressful movements in the tennis serve, but no research has been done with regard to the shoulder loading position (SLOP) in the tennis serve and its association with eye dominance (ED). Understanding the hand-eye coordination (HEC) system and how the hand and the eye mutually control and dependon each other remains challenging for visuomotor performance research. The visual influence of the hand and its importance in sports has commonly been documented, but scientific evidence is lacking with regard to the manual influence of the eye. A circular manual motor task with the thumb and the index finger, similar to the grip used on a tennis racket, seems to influence ED. The aim of this thesis is to contribute to a better understanding of the circular manually influenced eye dominance (CMIED) and its association with the personal SLOP in the tennis serve. This thesis is based on two studies (SI and SII) with data from a primary exploratory research study conducted at the Department of Sport Science, University of Innsbruck, with a total of thirty-one right-handed healthy tennis players. Study I (SI) compared two different hand-eye dominance (HED) screening tests: a. the conventional Porta Test (PT) and b. the new Circular Test (CT). Both tests were performed separately one-handed, namely with the right hand (T1), as well as two-handed, meaning additionally, with the left hand (T2). T1 and T2 investigated the data validity and reliability of the CT in comparison to the PT as to whethercrossed ED is more common than consistent ED.