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Abstract This study aimed to translate a web-based hamstring outcome score (HaOS) questionnaire to the Japanese context. First, the validity and reliability of the translated questionnaires were examined among Japanese athletes. Second, the association between the previous history of hamstring strain and HaOS was examined. The translation was performed according to internationally recognized methodologies. A total of 233 athletes were asked to complete the HaOS questionnaire, and four questions were added to examine the content validity of the questionnaire. Intraclass correlation coefficient (ICC) was calculated to evaluate the test–retest reliability. Internal consistency was determined by calculating Cronbach’s alpha values. The translated questionnaires had high acceptance and compliance rates, with a response rate of 84.4%. The ICC for each scale ranged from 0.80 to 0.93, and Cronbach's α from 0.72 to 0.96, confirming good reliability and high internal consistency. HaOS of the previous injury group (93.4 [78.9, 100]) was significantly lower than that of the healthy group (86.2 [68.1, 100]) (p

# Background There is a large population of young athletes who participate in gymnastics, and the prevention of injury in junior athletes is considered important. However, few studies have prospectively investigated the relationship between physical factors and the occurrence of injury. # Purpose To investigate the physical characteristics that are factors in the injury occurrence in elementary and junior high school gymnasts. # Study Design Prospective observational study. # Methods A total of 36 healthy young gymnasts (at national competition level) were enrolled in the study. Once a week for 23 weeks, injuries were prospectively investigated using self-report questionnaires under the supervision of a research staff. Joint range of motion (hip, ankle, shoulder, and wrist), tightness (Thomas test, Ely test, straight leg raise \[SLR], triceps surae, combined abduction test \[CAT], horizontal flexion test \[HFT]), and muscle elasticity (multifidus) were assessed to compare differences in physical function between injured and non-injured participants. # Results Injuries occurred most commonly in the wrist (42.1%), lower back (30.2%), and foot (9.5%) among males, whereas heel (22.2%), knee (16.0%), and lower back (12.8%) were the most common injury sites among females. Wrist injuries in male athletes showed decreased shoulder joint range of motion, and lower back injuries showed decreased hip and shoulder joint range of motion. Lower back injuries in female athletes showed decreased hip extension mobility. Heel and knee joint injuries in females also showed increased range of motion and decreased tightness. # Conclusions The results of this study indicate that the factors related to flexibility differ according to injury location. Further studies are required to clarify the physical factors that influence injury occurrence by examining the effects of the gymnasts’ muscle strength, age, individual factors, and left–right differences. # Level of Evidence 3

Although understanding the status of sports participation is essential for preventing injuries in young athletes, the level of specialization and relevant information in Japan is unknown. This study aimed to clarify the status of sports specialization and examine the relationships between specialization and training status in Japanese young soccer players. Four hundred Japanese young male soccer players were included. The players' parents completed a web questionnaire that consisted of three-point questions regarding specialization and training status (year, days of playing soccer, age when starting soccer). The level of specialization and accompanying information were calculated, and data were compared by specialization status. Of the participants, 53.8% demonstrated a high level of specialization. In addition, 74.5% considered soccer more important than other sports, 89.0% trained in soccer for more than 8 months of the year, and 74.0% had quit other sports to focus on soccer or played only soccer. The proportion of participants who played only soccer was significantly higher in the high-specialization group (37.6%) than in the moderate-specialization (22.5%; P < .01) and low-specialization (7.1%; P < .01) groups. By specialization status at grades 4 to 6 (9-12 years), 40.3% of participants demonstrated a high level of specialization. Young Japanese soccer players tend toward early specialization. Factors contributing to the high specialization level are being active throughout the year and rarely playing other sports. Training volume should be controlled, and an environment allowing young soccer players to participate in other sports simultaneously is needed, with early specialization being avoided.

OBJECTIVES This study evaluated prior sports participation and training frequency during elementary to high school and their association with acute and overuse injuries in Japanese college students currently majoring in physical education. METHODS This retrospective study included 292 students who completed questionnaires that assessed their type of sport participation (single sport or multiple sports), training frequency (number of days per week), and injury history (acute and overuse) during the elementary, junior high, and high school periods. RESULTS In total, 47.9% (95% confidence interval [CI]: 38.2–57.7) of elementary school-aged athletes played multiple sports; this decreased to 22.3% (95% CI: 14.1–30.4) in junior high school and 5.5% (95% CI: 1.0–9.9) in high school. There was a significant difference in the training frequency between those who had overuse injuries and not in elementary (p < 0.05), and junior high school (p < 0.05). CONCLUSIONS The results of this study suggest that participating in multiple sports through junior high school may lead to improved sports levels (i.e., participation in higher levels of competition). In addition, appropriate management of training frequency may help reduce the incidence of overuse injuries.

Monitoring the health of athletes is important for their protection, and questionnaires such as those produced by the Oslo Sports Trauma Research Center (OSTRC) are a valuable tool in this process. In 2020, several changes were made to the OSTRC questionnaires (OSTRC-O, OSTRC-H), including changes to the wording, structure, and logic of the original questionnaires. In the present study, the Japanese versions of the OSTRC questionnaires (OSTRC-O.JP, OSTRC-H.JP) were revised to meet the requirements of the updated versions and to analyse new and previously collected data to illustrate the impact of the changes on Japanese athletes. Proposed changes were categorized as minor or more substantial; minor changes were effected to the questionnaire instructions and to the wording of all four questions, and more substantial changes were made to the wording of question 2. The updated questionnaires also included changes to questionnaire logic and answer categories. To assess the consequences of the changes to the wording of question 2, 101 athletes were asked to complete the OSTRC-H.JP, which included both the original and updated versions of question 2, over 10 consecutive weeks. We calculated the number of health problems identified when new gatekeeper logic was and was not applied, using 1585 OSTRC-H.JP responses to assess the consequences of the changes to the questionnaire logic. The kappa coefficient, which measures the level of agreement between the responses to question 2 of the original and updated versions, was high. By applying gatekeeper logic, there was a remarkable reduction in the number of injuries and illnesses among all health problems but less reduction in substantial health problems and time loss health problems. These changes will make it easier for Japanese athletes to complete the questionnaires and improve the quality of collected data.

OBJECTIVES Detection of the frequency or intensity of high-impact movements during volleyball match would help understand physical load causing the injuries. The present study aimed to classify different volleyball-specific high-impact movements based on the measurement of trunk acceleration in a volleyball match as a cross-sectional study. METHODS Linear accelerations of six female volleyball players were measured during a single volleyball match. The instances at which >4G and >6G of resultant acceleration was generated were detected. Movements recorded with a synchronized video were also detected and categorized. Counts (cases) and frequencies (cases/min) of the detected movements were calculated, and the resultant and each directional acceleration among the top seven volleyball-specific detected movements were compared. RESULTS For attackers, 361 and 97 movements were detected for the resultant acceleration thresholds over 4G and 6G, respectively. Landing, takeoff and running were the top three detected movements in both thresholds. Landing was the most frequently observed high-impact movement, and the ratio of landing over 6G was greater among all detected movements compared with the ratios of landing over 4G threshold. For receivers, 297 and 38 movements were detected for the resultant acceleration thresholds over 4G and 6G, respectively. Running, steps on the spot, and steps forward or backward were the top three detected movements. The top seven detected volleyball-specific movements generating over 4G were landing after blocking, landing after spiking, takeoff before spiking, takeoff before blocking, stationary steps during receiving, steps forward or backward during receiving and sidesteps during receiving. Resultant and vertical accelerations of landing after spiking were significantly greater than those of the other six movements (p < 0.001). CONCLUSIONS Using the results of present study, we were able to estimate the physical load causing injuries during a real volleyball match.

This study aimed to translate and culturally adapt the Oslo Sports Trauma Research Center Overuse Injury Questionnaire (OSTRC-O) and the Oslo Sports Trauma Research Center Questionnaire on Health Problems (OSTRC-H) into the Japanese context. The validity and reliability of these translated questionnaires examining overuse injuries and health problems among Japanese university athletes were also examined. The translation was performed following an internationally recognized methodology. A total of 145 athletes were tracked over 10 consecutive weeks and four questions were added in the 10th week to examine the questionnaires' content validity. Test-retest analysis for reliability was performed 24-72 hours after the 10th week of registration. Internal consistency was determined by calculating Cronbach's a during the cohort study. No major disagreements were found in the translation process. The translated questionnaires had high acceptance and compliance, with an average response rate of over 80% throughout the 10-week cohort study. Most participants reported that the questionnaires were not difficult to complete, there were no items they wanted to change or add, and that the web-based technique worked effectively. Good test-retest reliability and high internal consistency was observed in the translated questionnaires. The translated questionnaires were found to be valid, reliable, and acceptable for medically monitoring Japanese athletes.

The purpose of the present study was to translate and modify the Oslo Sports Trauma Research Centre (OSTRC) overuse injury questionnaire into Japanese and validate it among Japanese athletes through a longitudinal survey. A modified back-translation method was used to translate the questionnaire from English to Japanese. The longitudinal survey was performed in 29 female college swimmers who were followed up for more than 24 consecutive weeks. The response rate to the 24 weekly questionnaires was 88.8% (95% confidence interval [CI]: 85.2-92.3). Internal consistency was measured by using Cronbach's alpha (0.73 (0.69-0.77)). The anatomical areas most frequently affected by overuse injuries were the lower back (average weekly prevalence: 27.6%, 95% CI: 25.1-30.1), shoulder (16.0%, 95% CI: 13.7-18.2), knee (9.9%, 95% CI: 7.7-12.0), and ankle (9.0%, 7.6-10.5). The severity score showed that knee (22.5, range: 6-65), ankle (21.5, range: 6-67), and lower back (20.7, range: 6-80) injuries had the greatest impact. The Japanese version of the modified OSTRC overuse injury questionnaire demonstrated reliability and validity based on the results of internal consistency and trend of injury of the swimmers. The participants in the present study did not have substantial injuries or time-loss injuries and continued practicing and competing, despite these minor injuries. Although knee and ankle injuries do not occur as often as lower back and shoulder injuries, these injuries often had a greater impact on swimmers when they did occur.

The purpose of this study was to measure the change in hamstring muscle thickness between contracting and relaxing conditions following a return to sports after a hamstring muscle strain and thereby evaluate muscle function. Six male track and field sprinters participated in this study. All had experienced a prior hamstring strain injury that required a minimum of 2 weeks away from sport participation. Transverse plane scans were performed at the following four points on the affected and unaffected sides under contracting and relaxing conditions: proximal biceps femoris long head, proximal semitendinosus, middle biceps femoris long head, and middle semitendinosus. The results demonstrated an increase in the thickness of the middle biceps femoris long head and middle semitendinosus regions on the unaffected side with contraction, whereas the affected side did not show a significant increase. The proximal semitendinosus muscle thickness was increased with contraction on both the unaffected and the affected sides. By contrast, the proximal biceps femoris muscle thickness did not show a significant increase on both sides. The results of this study show that evaluation of muscle thickness during contraction may be useful for assessing the change in muscle function after a hamstring muscle strain injury.

Raising awareness on a disorder is important for its prevention and for promoting public health. However, for sports injuries like the anterior cruciate ligament (ACL) injury no studies have investigated the awareness on risk factors for injury and possible preventative measures in the general population. The sources of information among the population are also unclear. The purpose of the present study was to identify these aspects of public awareness about the ACL injury.A questionnaire was randomly distributed among the general population registered with a web based questionnaire supplier, to recruit 900 participants who were aware about the ACL injury. The questionnaire consisted of two parts: Question 1 asked them about their sources of information regarding the ACL injury; Question 2 asked them about the risk factors for ACL injury. Multivariate logistic regression was used to determine the information sources that provide a good understanding of the risk factors.The leading source of information for ACL injury was television (57.0%). However, the results of logistic regression analysis revealed that television was not an effective medium to create awareness about the risk factors, among the general population. Instead "Lecture by a coach", "Classroom session on Health", and "Newspaper" were significantly more effective in creating a good awareness of the risk factors (p < 0.001).

Some studies have listed motions that may cause Osgood-Schlatter disease, but none have quantitatively assessed the load on the tibial tubercle by such motions.To quantitatively identify the load on the tibial tubercle through a biomechanical approach using various motions that may cause Osgood-Schlatter disease, and to compare the load between different motions.Eight healthy male subjects were included. They conducted 4 types of kicks with a soccer ball, 2 types of runs, 2 types of squats, 2 types of jump landings, 2 types of stops, 1 type of turn, and 1 type of cutting motion. The angular impulse was calculated for knee extension moments ≥1.0 Nm/kg, ≥1.5 Nm/kg, ≥2.0 Nm/kg, and ≥2.5 Nm/kg. After analysis of variance, the post-hoc test was used to perform pairwise comparisons between all groups.The motion with the highest mean angular impulse of knee extension moment ≥1.0 Nm/kg was the single-leg landing after a jump, and that with the second highest mean was the cutting motion. At ≥1.5 Nm/kg, ≥2.0 Nm/kg, and ≥2.5 Nm/kg, the cutting motion was the highest, followed by the jump with a single-leg landing. They have a large load, and are associated with a higher risk of developing Osgood-Schlatter disease. The mean angular impulse of the 2 types of runs was small at all the indicators.Motions with a high risk of developing Osgood-Schlatter disease and low-risk motions can be assessed in further detail if future studies can quantify the load and number of repetitions that may cause Osgood-Schlatter disease while considering age and the development stage. Scheduled training regimens that balance load on the tibial tubercle with low-load motions after a training day of many load-intensive motions may prevent athletes from developing Osgood-Schlatter disease and increase their participation in sports.

Background: The risk of anterior cruciate ligament (ACL) injury is higher in female soccer players than in male soccer players. The most common reason for non-contact ACL injury has been found to be a cutting or stopping maneuver combined with deceleration and landing from a jump. In a previous study, there was no difference in the incidence of ACL injury between offensive and defensive players and in the risk of ACL injury between goalkeepers and other players. Recently studies reported that the most frequent injury situation was pressing in male players. However, the most common type of situation associated with ACL injury in female soccer players has not been clarified. Objectives: The purpose of the present study was to identify the most common type of situation associated with ACL injury in female soccer players. Methods: We handed out questionnaires to 80 female soccer players with a history of ACL injury (90 ACL injuries). The players were asked about the injury characteristics, injury circumstance, maneuver being performed when the injury occurred, and playing type associated with the injury. The players responded to the questionnaire under the guidance of the medical staff of each team. Results: The 80 female soccer players reported a total of 90 ACL injuries during soccer. Among 55 non-contact injuries, 29 (55%) occurred during a cutting maneuver and 22 (44%) occurred during pressing. On assessing the frequency distributions of playing type (pressing vs. others) and body contact (contact vs. nocontact), we found that non-contact injuries at pressing were significantly more common than contact injuries at pressing (odds ratio: 3.03; 95% confidence interval, 1.11 - 8.25, P = 0.036) Conclusions: ACL injury often occurs as non-contact injury during pressing at the time of defense, regardless of the playing area, in female soccer players. [ABSTRACT FROM AUTHOR]

Athletes with non-contact anterior cruciate ligament tears have common features in the sagittal plane; namely, the body's center of mass (COM) is located posterior to the base of support, the trunk and knee joints are extended, and the hip angle is flexed. However, the relationships among these variables have not been assessed in field-based movements. This study sought to determine relationships between distances from the COM to the base of support and the trunk, hip, and knee positions in women while playing soccer. Sixty events (29 single-leg landing and 31 single-leg stopping events) were analyzed using two-dimensional video analysis. The relationships among the measurement variables were determined using the Pearson's product-moment correlation coefficient, and stepwise multiple linear regression models were used to explore the relationships between the COM position and the kinematic variables. The distance from the COM to the base of support displayed a moderate negative relationship with the trunk angle (r = - 0.623, p < .0001, r2 = 0.388) and a strong positive relationship with the limb angle (r = 0.869, p < .0001, r2 = 0.755). The limb, knee, and trunk angles were selected in the best regression model (adjusted r2 = 0.953, p < .0001, f2 = 20.277). These findings suggest that an increased trunk angle and a decreased limb angle at initial contact are associated with a safer COM position. Neuromuscular training may be useful for controlling the trunk and lower limb positions during dynamic activities. [ABSTRACT FROM AUTHOR]

Objective: The objective is to assess the in vivo knee secondary motions intrinsic to flexion in isolation from actual displacements during a landing activity. For this purpose a "static zero position", which denotes the normal tibiofemoral position to the static flexion angle, was introduced to describe the intrinsic secondary motion. Methods: The three-dimensional motion data of the healthy knee were collected from 13 male and 13 female young adults by using an auto motion analysis system and point cluster technique. First, the relationship between flexion and secondary motion in the static state was determined during a single-leg quasistatic squat. The static zero position during a single-leg drop landing was then calculated by substituting the flexion angle into the flexion-secondary relational expression obtained. Results: After the foot-ground contact, the estimated static zero positions shiftedmonotonically in valgus, internal rotation, and anterior translation in the case of both the male and female groups. For the time-course change, noticeable differences between the actual displacement and estimated static zero position were found from the foot-ground contact up to 25 ms after the contact for the valgus/varus and external/internal rotation, and between 20 and 35 ms after the contact for the anterior/posterior translation. Summary: The static zero position demonstrated relatively modest but not negligible shift in comparison with the actual displacement. The intrinsic tibiofemoral motion, or baseline shift,would beworth taking into account when examining the fundamental function and injury mechanics of the knee during an impulsive activity. [ABSTRACT FROM AUTHOR]