###### Abstract  
Background: In rugby, the shoulder contributes to attack/defence during collisions, tackling, falling, scrummaging, and mauiling. We investigated the frequency, tissue, and pathology type of shoulder injuries per player position among professional South African rugby players, and compared injury severity in the context of momentum, intensity, and collision variables. Methods: A prospective study collecting shoulder injury data of 80 male Super Rugby players (>18 years) over 4 seasons (2018-2021). Players wore a Catapult Evo GPS unit during training and match-play, recording performance variables and collision forces during injury. We collected tissue and pathology types of injury from players' medical files, clinical examinations, and special investigations. Results: Shoulder injuries contributed to 17% of all injuries, ranging from 2 to 34% per year. Forwards (63%) sustained most shoulder injuries, specifically locks (30%). Acromioclavicular (AC) joint (47%) was mostly involved, and ligament/joint capsule (65%) was the most common tissue type injured. Injuries with the highest average momentum resulted in players suffering minimal to mild severity injuries (1-7 days time-loss). Backs (631.15 kg m/s) required less momentum than forwards (816.00 kg m/s) to suffer injuries resulting in >28 days time-loss (\(p\) = 0.008). Backs encountered higher match intensity (67.76 m/min, \(p\) = 0.031) and highest average collisions (0.28/min) without suffering more severe (>28 days time-loss) injuries. Match intensity of >60 m/min resulted in more than 55% of shoulder injuries. Conclusion: One in six injuries in this cohort was shoulder-related. Forwards, specifically locks, sustained most shoulder injuries. The AC joint was the tissue type that mainly contributed. Backline players were involved in higher velocity contact, game intensity, and collision frequency but suffered fewer injuries. However, they required less momentum to sustain more severe injuries. shoulder injuries; rugby; contact; GPS; severity +
Footnote †: _Applied_
efforts (high-speed running, accelerations, decelerations), jumping, change of directions, static exertions, and low-velocity high-force efforts (tackle, ruck, maul, scrum) [1, 7, 8, 9, 10]. The combination of speed, strategy, and strength skills is also associated with a high proportion of traumatic injuries that may occur during training or match-play [11, 12]. In rugby, the player's shoulder is typically the first point of contact in physical collisions and technical contests such as tackling, cleaning out a ruck, scrummaging, and mailing [4, 7, 13, 14]. The tackle is the match event responsible for almost all shoulder injuries (46-90%) [12, 15, 16, 17, 18, 19, 20]. In rugby, tackling is a core skill of defence for all players and is associated with a high risk of injury [21, 22, 23, 24, 25]. The high risk of shoulder injuries during tackle events may result from its unparalleled range of motion [16, 26]. These physical demands on the shoulder are also position specific. A previous study found significant differences in player injury profiles, as well as between different positions. The study hypothesised that there are likely position-specific differences determined by the technical and physical requirements of each position [27]. The different positional requirements of rugby players, with specific reference to locomotor and contact skills, demand specific technical actions during attack or defence plays [5, 7, 14]. For example, only forwards are involved in static exertion periods (scrums). In the backline, collision events commonly occur when performing high-intensity running [1, 5, 7, 12, 13]. As a consequence of these demands, the shoulder is the second most commonly injured body site (28% of all injuries) after the knee [15, 27] and causes the second-highest time-loss injuries after the knee joint [28].