To examine risk factors for shoulder injuries with or without history of the injuries using the stratification analysis for collegiate rugby players. 71 elite rugby players from one university rugby club joined in the preseason medical screening related to their shoulder joints, including basic demographics, history of injuries, and physical findings at that time. Subsequently, the occurrence of shoulder injuries was recorded during four playing seasons. Analysis was stratified with or without history of the injuries; player without the past history of injury, 47 players; player with the past history of injury, 24 players. As a result of all players with the past history, 13 players sustained the shoulder injuries. Internal rotational range of motion [IR ROM] (OR, 1.5; 95%CI, 1.13-1.96; p=0.004), external rotational range of motion [ER ROM] (OR, 1.9; 95%CI, 1.21-2.87; p=0.005), horizontal flexion range of motion [HF ROM] (OR, 1.3; 95%CI, 1.03-1.64; p=0.025), IR muscle strength (OR, 0.4; 95%CI, 0.20-0.65; p=0.001) and rugby experience (OR, 1.2; 95%CI, 1.02-1.46; p=0.032) were associated with the shoulder injuries. On the other hand, 10 players sustained injuries of the players without the past history of injury. IR muscle strength (OR, 0.3; 95%CI, 0.11-0.72; p=0.008) and rugby experience (OR, 1.4; 95%CI, 1.11-1.66; p=0.003) were associated with the shoulder injuries. This study clearly showed that IR, ER, HF ROM, IR muscle strength and rugby experience were important initial risk factors for shoulder injuries. Moreover, IR muscle strength and rugby experience were important recurrence risk factors for shoulder injuries.

The purpose of this study was to describe the incidence, severity, and burden of injuries in Japanese male collegiate rugby union players. Initially, 170 male collegiate rugby union players from one university club were registered in this epidemiological surveillance study. The occurrence of injuries was recorded by a team medical staff during the 2017–2021 playing seasons. The incidence of injuries was 6.87 injuries/1000 h. This incidence was significantly higher during matches (100.37 injuries/1000 h) than that during training (3.63 injuries/1000 h). The severity of injuries was 31.0 days, and there were no significant differences between matches and training, or forwards and backs. The burden of injuries was 213.1 days/1000 h. This burden was significantly higher during matches (2887.8 days/1000 h) compared to training (120.1 days/1000 h). Matches had higher incidence of ankle sprain/ligament injuries (15.80 injuries/1000 h) and concussion (15.36 injuries/1000 h). The most common injury site was the ankle (1.24 injuries/1000 h). However, the greatest severity and burden were observed for knee injuries (severity: 59.1 days, burden: 48.6 days/1000 h). Furthermore, the greatest burden of injury type was knee sprain/ligament injuries (39.4 days/1000 h). In addition, the incidence of acromioclavicular joint injury was significantly higher in forwards, whereas hamstring strain was significantly higher in backs. The common injury mechanisms identified were being tackled (16.0%) and tackling (14.7%), followed by overuse (12.1%). In order to improve the player welfare of the Japanese collegiate rugby union players, it is necessary to work on the prevention strategy considering the injury profile.