[Purpose] The purpose of the present study was to establish the intra- and inter-rater reliability of measurement of extensor strength in the maximum shoulder abducted position and internal rotator strength in the 90° abducted and the 90° external rotated position using a hand-held dynamometer. [Subjects and Methods] Twelve healthy volunteers (12 male; mean ± SD: age 19.0 ± 1.1 years) participated in the study. The examiners were two students who had nonclinical experience with a hand-held dynamometer measurement. The examiners and participants were blinded to measurement results by the recorder. Participants in the prone position were instructed to hold the contraction against the ground reaction force, and peak isometric force was recorded using the hand-held dynamometer on the floor. Reliability was determined using intraclass correlation coefficients. [Results] The intra- and inter-rater reliability data were found to be “almost perfect”. [Conclusion] This study investigated intra- and inter-rater reliability and reveald high reliability. Thus, the measurement method used in the present study can evaluate muscle strength by a simple measurement technique.

[Purpose] The purpose of present study was to establish the same-session and between-day intra-rater reliability of measurements of extensor strength in the maximum abducted position (MABP) using hand-held dynamometer (HHD). [Subjects] Thirteen healthy volunteers (10 male, 3 female; mean ± SD: age 19.8 ± 0.8 y) participated in the study. [Methods] Participants in the prone position with maximum abduction of shoulder were instructed to hold the contraction against the ground reaction force, and peak isometric force was recorded using the HHD on the floor. Participants performed maximum isometric contractions lasting 3 s, with 3 trials in one session. Between-day measurements were performed in 2 sessions separated by a 1-week interval. Intra-rater reliability was determined using intraclass correlation coefficients (ICC). Systematic errors were assessed using Bland-Altman analysis for between-day data. [Results] ICC values for same-session data and between-day data were found to be “almost perfect”. Systematic errors not existed and only random error existed. [Conclusion] The measurement method used in this study can easily control for experimental conditions and allow precise measurement because the lack of stabilization and the impact of tester strength are removed. Thus, extensor strength in MABP measurement is beneficial for muscle strength assessment.

The koshiwari (Sumo Squat) is a traditional exercise used for basic training for sumo wrestling, the national sport of Japan. This study compares and analyzes the kinetics and kinematics of the koshiwari and squat with wide-stance (WSQ) to provide insight related to the mechanical features of the koshiwari. Optical three-dimensional automatic analysis instruments were used to measure movements of 11 men during exercises. A force platform was used to measure floor reactions. Two movements were analyzed: koshiwari and WSQ. The koshiwari and WSQ were compared as analytical objectives, using paired t-tests corresponding to correction joint angles, angular impulse, and joint torques with the level of significance set under 5%. Koshiwari was found to involve markedly greater excursions of abduction (maximum and minimum angle, correction angle to 20%-60%) and external rotation (maximum and minimum angle) at the hip compared with the WSQ, as well as markedly less hip flexion (maximum angle, correction angle 10%-90%) and torso forward tilt (maximum angle, correction angle 30%-100%). Koshiwari also involved greater extension-flexion axis, abduction-adduction axis, external rotation-internal rotation axis angular impulse and flexion (10%-100%), adduction (40%-60%), and external rotation (20%) torques at the hip than WSQ exercises. Results suggest that hip external rotation torque is attributable to hip external rotator muscle activity. The activity can apparently reduce the risk of ACL (Anterior cruciate ligament) injuries and patellofemoral pain syndrome and improve athletic performance.

Background: Rugby is a high risk of injury to the ankle, but epidemiological data on ankle injury is limited to specific competition levels and generations. This study aimed to clarify the epidemiological characteristics of ankle sprain by longitudinally investigating the incidence, severity and burden of ankle sprains in men's collegiate rugby players. Methods: The study recorded ankle sprains in rugby matches and training across three seasons from 2017 to 2019, investigating 128 male collegiate rugby players.Results: The incidence of ankle sprain was 1.21 injuries/1000 Player-hours (1000 PHs), and the risk of occurrence during matches (18.18 injuries/1000 PHs) was 25.6 times higher than during training (0.71 injuries/1000 PHs). Thus, it was thought that reducing the incidence of ankle sprains during matches would contribute greatly to reducing the loss of competition time due to injury of team members. The results suggested that the main injury mechanism was related to contact play and steps, and that contact skills and physical fitness characteristics were also involved in the risk of sprains. The incidence of ankle sprains in collegiate rugby players was higher than that reported in a previous study on professional-level players, and the rate of initial sprains was high in this study. Conclusions: This suggests that prevention of ankle sprains is important in university age rugby players.