Kinematics, Kinetics and Muscle Activity Analysis during Single-leg Drop-jump Landing Followed by an Unanticipated Task: Focusing on Differences in Neurocognitive Function.

Background: Lower neurocognitive function is a risk factor for anterior cruciate ligament (ACL) injury. However, the mechanism by which lower neurocognitive function increases the risk of ACL injury remains unclear. Purpose: To clarify the effect of differences in neurocognitive function on landing mechanics during a single-leg drop-jump landing motion followed by an unanticipated task. Study Design: Cross-sectional study. Methods: Fifteen collegiate female athletes were recruited (20.1 ± 1.3 years, 166.6 ± 7.3 cm, 60.6 ± 6.9 kg) and were divided into two groups (the high-performance (HP) group and the lower-performance (LP) group) using the median Symbol Digit Modalities Test (SDMT) score. Three-dimensional motion analysis was employed for the analysis during the experimental task of a single-leg drop-jump followed by an unanticipated landing task from a 30-cm high box. Joint angular changes of the trunk, pelvis, hip, and knee were calculated within the interval from initial contact (IC) to 40ms. Knee and hip moments were calculated as the maximum values within the interval from IC to 40ms. Surface electromyography data from key muscles were analyzed 50ms before and after IC. Independent t-tests were used to compare the effects of different neurocognitive function on the measurement items. Statistical significance was set at p < 0.05. Results: The SDMT score was significantly higher in HP group (HP: 77.9 ± 5.5; LP: 66.0 ± 3.4; p < 0.001). The LP group had a significantly greater trunk rotation angular change to the stance leg side (HP: 0.4 ± 0.8; LP: 1.2 ± 0.4; p = 0.020). There were no significant differences between the two groups in terms of joint moments, and muscle activities. Conclusion: Differences in neurocognitive function by SDMT were found to be related to differences in motor strategies of the trunk in the horizontal plane. Although trunk motion in the sagittal and frontal planes during single-leg drop-jump landing increases the ACL injury risk by affecting knee joint motion, the effect of trunk motion in the horizontal plane remains unclear. Level of Evidence: 3© The Authors.

Injury Prevalence among Young Elite Baseball Players.

This study aimed to describe the injury profiles of young Korean baseball players according to position and age as the proportion and distribution of injuries based on playing position and age remains unclear. A total of 271 elite youth baseball players aged 8 to 16 years were divided into two groups: elementary school (ES) (n = 135) and middle school (MS) (n = 136). The participants' basic, baseball practice, and injury information were collected. Injuries in the MS group were not limited to the elbow and shoulder, and injury prevalence varied by age group and baseball position. The most injured body region in the ES group was the elbow joint, regardless of the position. In contrast, the most injured body region in the MS group was the lower back, except for infielders whose elbows were the most injured. Additionally, the MS group was more likely to experience injuries to the lower back (OR = 4.27, 95% CI = 2.47-7.40), shoulder (OR = 1.93, 95% CI = 1.08-3.43; p = 0.024), and knee (OR = 2.15, 95% CI = 1.17-3.94; p = 0.012). Our findings indicate that excessive practice and a lack of rest during MS (growth spurt period) can significantly increase the risk of lower back problems in young baseball players.

Analysis of trunk rotation during baseball batting with lumbar disc degeneration.

Lower back pain (LBP) is common among baseball players, and the occurrence of lumbar intervertebral disc degeneration is high. The dynamic load on the lumbar spine due to the postures and movements characteristic of baseball is suspected of aggravating LBP caused by degeneration, but the difference in batting action between players with and without degeneration is not known. The purpose of this study was to investigate the difference in batting motion in the presence and absence of lumbar disc degeneration (LDD). The subjects were 18 male baseball players belonging to the University League Division I: seven with disc degeneration and 11 without. The motion task analyzed tee batting. The items examined were the angles of rotation of shoulder, pelvis, hip, and twisting motion; rotation angular velocity; time to maximum angular velocity; and muscle activity potentials of the bilateral latissimus dorsi, erector spinae, multifidus, external oblique, internal oblique, rectus abdominis, and gluteus medius muscles; at each stage of batting action. There were significant differences between the shoulder and pelvis in rotation angle, time to maximum angular velocity, and muscle activity in the presence and absence of LDD, and in the time to maximum angular velocity between the shoulder and pelvis. We infer that these differences are characteristic of batting motion due to LDD.

Taurine supplementation enhances endurance capacity by delaying blood glucose decline during prolonged exercise in rats.

Taurine enhances physical performance; however, the underlying mechanism remains unclear. This study examined the effect of taurine on the overtime dynamics of blood glucose concentration (BGC) during endurance exercise in rats. Male F344 rats were subjected to transient treadmill exercise until exhaustion following 3 weeks of taurine supplementation or non-supplementation (TAU and CON groups). Every 10 min during exercise, BGC was measured in blood collected through cannulation of the jugular vein. Gluconeogenesis-, lipolysis-, and fatty acid oxidation-related factors in the plasma, liver, and skeletal muscles were also analyzed after 120-min run. Exercise time to exhaustion was significantly longer with taurine supplementation. BGC in the two groups significantly increased by 40 min and gradually and significantly decreased toward the respective exhaustion point. The decline in BGC from the peak at 40 min was significantly slower in the TAU group. The time when the once-increased BGC regressed to the 0-time level was significantly and positively correlated with exercise time until exhaustion. At the 120-min point, where the difference in BGC between the two groups was most significant, plasma free fatty acid concentration and acetyl-carnitine and N-acetyltaurine concentrations in skeletal muscle were significantly higher in the TAU group, whereas glycogen and glucogenic amino acid concentrations and G6Pase activity in the liver were not different between the two groups. Taurine supplementation enhances endurance capacity by delaying the decrease in BGC toward exhaustion through increases of lipolysis in adipose tissues and fatty acid oxidation in skeletal muscles during endurance exercise.

The effects of using a combination of static stretching and aerobic exercise on muscle tendon unit stiffness and strength in ankle plantar-flexor muscles.

The purpose of the present study was to investigate the effects of using a combination of static stretching and aerobic exercise on muscle tendon unit stiffness and muscle strength in the ankle plantar-flexor muscles. Fifteen healthy males (23.3 ± 2.7 years, 170.3 ± 6.5 cm, 64.9 ± 8.7 kg) received three different interventions, in random order. Intervention 1 received 10 min of aerobic exercise after five cycles of one minute of static stretching. Intervention 2 received 10 min of aerobic exercise before the static stretching. Intervention 3 received 5 min of aerobic exercise both before and after the static stretching. The range of motion of ankle dorsiflexion, stretch tolerance, muscle tendon unit stiffness, peak torque of ankle plantarflexion, and the amplitude of electromyography were measured. In all interventions, the range of motion and stretch tolerance significantly increased (p < 0.05), but muscle tendon unit stiffness decreased significantly for all interventions (p < 0.05). Peak torque of ankle plantar flexion and amplitude of electromyography significantly increased for Interventions 1 and 3 (p < 0.05), while these significantly decreased for Intervention 2 (p < 0.05). These data indicated that range of motion and stretch tolerance were increased, but muscle tendon unit stiffness was decreased regardless of the order of static stretching and aerobic exercise. Aerobic exercise after static stretching increased the peak torque and amplitude of electromyography.

Chronological changes in neuromuscular cooperativeness before and after muscle fatigue loading using the silent period of the quadriceps and hamstrings in young female athletes.

[Purpose] Understanding the neuromuscular cooperativeness functions when an athlete is fatigued is essential in preventing sports injuries and examining post-injury return standards. This study aimed to investigate the kinds of changes in neuromuscular cooperativeness before and after fatigue loading. [Participants and Methods] Fifteen female university athletes were examined for chronological changes in neuromuscular cooperativeness. Muscle fatigue loading was performed using BIODEX (180°/s) during knee flexion and extension exercises on one side. Surface electromyography of the rectus femoris and biceps femoris was performed on both sides before and immediately, 5 min, 10 min, and 15 min after loading. The switching silent period and pre-motor time were calculated from the electromyographic waveforms to indicate neuromuscular cooperativeness. [Results] The switching silent periods in the loading side immediately and 5 min after loading were significantly prolonged compared with that before loading. [Conclusion] Muscle fatigue loading instantaneously prolonged the switching silent period and decreased the neuromuscular cooperativeness. Furthermore, recovery generally occurred within 10 minutes after loading.

Effect of temporary school closure due to COVID-19 on musculoskeletal function in elementary school children.

Objective: In 2020, coronavirus disease-2019 (COVID-19) became the cause of a pandemic. In response, the Japan Sports Agency issued warnings about secondary damage to health, such as the threat to physical and mental well-being due to the lack of exercise in this situation. In this study, we report on cross-sectional and longitudinal examinations of standing trunk flexion to evaluate how temporary long-term school closures affected musculoskeletal function in elementary school students. Patients and Methods: All children in one public elementary school in T-city during the school years 2019 and 2020 were included in this study. A digital forward flexion meter was used to measure standing trunk flexion. Results: In this study, 284 (284/289: 98.3%) and 266 (266/274: 97.1%) children in school years 2020 and 2019, respectively, were found to have valid data for cross-sectional analysis. The standing trunk flexion did not show significant differences between grades or sexes. In the longitudinal analysis, the results of the comparison of standing trunk flexion in children for two consecutive years revealed significant differences only between grades 3 and 4 (P<0.05) and between girls in grades 3 and 4 (P<0.01), but no significant differences in other grades or among boys or girls were observed. Conclusion: Initially, we expected that there would be a difference in the results of functional assessment using standing trunk flexion depending on the period of absence from school. However, the results of this study showed no significant changes in standing trunk flexion. Moreover, since children's musculoskeletal functions may be affected by various factors during the COVID-19 pandemic, they should be carefully monitored in the future.

Differences in Muscle Activities and Kinematics between Forefoot Strike and Rearfoot Strike in the Lower Limb during 180° Turns.

BACKGROUND: A forefoot strike (FFS) could be a safer landing technique than a rearfoot strike (RFS) during a cutting motion to prevent anterior cruciate ligament (ACL) injury. PURPOSE: This study aimed to determine the joint angles, ground reaction force (GRF), and muscle activity levels associated with FFS and RFS landings during 180° turns. STUDY DESIGN: Cross-sectional study. METHODS: Fourteen male soccer players from the University of Tsukuba football (soccer) club participated in this study. The FFS consisted of initial contact with the toes on the force plates followed by the rearfoot; meanwhile, the initial contact was performed with the heels on the force plates followed by the forefoot for the RFS. Ankle, knee, and hip joint angles were recorded using a three-dimensional motion capture system. GRFs were measured using a force plate. Gluteus medius (GM), rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), biceps femoris (BF), tibialis anterior (TA), and lateral gastrocnemius (GL) activities were measured by electromyography. RESULTS: The activities of GM, GL, and ST from initial contact to early periods during landing into the ground with the FFS are larger than those with RFS. In addition, the results showed significant differences in lower-limb angles and GRFs between the FFS and RFS. CONCLUSION: These results suggest that there might be differences in ACL injury risk during a 180° turn between the FFS and the RFS pattern. An investigation into the grounding method that prevents injury is necessary in future studies. LEVELS OF EVIDENCE: Level 3b.

Male collegiate soccer athletes with severe ankle laxity display increased knee abduction during side-cutting tasks compared to those with only perceived ankle instability.

This study aimed to examine lower limb kinematics during a side-cutting task in male collegiate soccer athletes with severe ankle laxity. Forty-seven participants with a history of ankle sprains and perceived ankle instability were categorized into non-laxity (n = 17), laxity (n = 19), and severe laxity (n = 11) groups using stress radiography tests. Three-dimensional kinematic data during the stance phase of a 45° side-cutting task were analysed. The frontal plane kinematics of the knee significantly differed between the three groups (p < 0.05). The severe laxity group exhibited a greater abduction angle than the non-laxity group (p < 0.05). The horizontal and sagittal plane kinematics of the rearfoot differed between the three groups during the end of the stance phase (p < 0.05). Our data suggest that collegiate soccer athletes with both perceived ankle instability and severe ankle laxity exhibit greater knee abduction movement during a 45° side-cutting task compared to those with only perceived ankle instability.

Effects of Active and Passive Warm-ups on Range of Motion, Strength, and Muscle Passive Properties in Ankle Plantarflexor Muscles.

ABSTRACT: Takeuchi, K, Takemura, M, Nakamura, M, Tsukuda, F, and Miyakawa, S. Effects of active and passive warm-ups on range of motion, strength, and muscle passive properties in ankle plantarflexor muscles. J Strength Cond Res 35(1): 141-146, 2021-The purpose of this study was to examine the effects of active and passive warm-ups on flexibility and strength of calf muscles. Fourteen healthy males (age: 23.1 ± 2.6 years, height: 172.7 ± 5.6 cm, and body mass: 64.5 ± 7.0 kg) performed 3 types of warm-ups respectively for 10 minutes in a random order: an active warm-up by pedaling a cycling ergometer, an active warm-up doing repeated isometric contractions, and a passive warm-up in a hot water bath. To assess flexibility, range of motion (ROM) of ankle dorsiflexion, passive torque of ankle plantarflexion, and muscle tendon junction (MTJ) displacement were measured and then muscle tendon unit (MTU) stiffness was calculated. After the flexibility assessment, peak torque during maximum voluntary isometric contraction was measured to assess the isometric strength. These data were compared before and after each warm-up. As a result, all 3 types of warm-ups increased ROM (p < 0.05) and passive torque at terminal ROM (p < 0.01), but there were no significant changes in MTU stiffness or MTJ displacement. The active warm-up by pedaling a cycling ergometer increased peak torque during isometric contraction (p < 0.05), whereas the other warm-ups did not show significant alterations. In conclusion, the active warm-up with aerobic exercise increased flexibility and strength of the calf muscles.

Four-year musculoskeletal examinations among elementary and junior high school students across a single city.

Objective: In 2016, Japan started conducting musculoskeletal examinations that included "limb status" of students as an essential item. Our institution implemented a unified musculoskeletal examination for all public elementary and junior high schools in T-city. In this study, we aimed to report the progress in the past 4 years. Patients and Methods: The Tsukuba Childhood Locomotive-Organ Screening Sheet (T-CLOSS), which is a questionnaire that includes some nationwide-recommended questions, was prepared and distributed to students. Results of the questionnaires were analyzed, and the orthopedic surgeon conducted examinations for the extracted items. From these questionnaires, the ratio of each item, rate of advisory for screening, and content of the advisory were investigated. Results: During 2016-2019, musculoskeletal examinations were conducted in every public schools, with nearly 20,000 students in T-city. The consultation advisory rate was 6.7% in 2019. Of the 524 students who received the third screening recommendation, the actual consultation rate was 248 (40.8%). After the third screening, the proportion of students requiring treatment and outpatient visits was 46.7% (n=248), which accounted for 1.2% of all elementary and junior high school students in the city. Conclusion: We reported the results of 4-year musculoskeletal examinations in a city. In our screening, we distributed a uniform questionnaire throughout the city, and orthopedic surgeons performed secondary examinations of identified students in all schools. This appears to be an advanced effort to prevent musculoskeletal impairment in students. We hope to conduct more sophisticated musculoskeletal examinations using our results, aiming at early detection, early treatment, and improvement of musculoskeletal function in elementary and junior high school students.

Ankle laxity affects ankle kinematics during a side-cutting task in male collegiate soccer athletes without perceived ankle instability.

OBJECTIVES: To investigate whether ankle joint laxity alone influences lower limb kinematics during a side-cutting task. DESIGN: A cross-sectional study. SETTING: Sports medicine research laboratory. PARTICIPANTS: In total, 66 male collegiate soccer players with history of ankle sprains with no perceived ankle instability were categorised into three groups: no-laxity copers (n = 26), laxity copers (n = 23), and severe-laxity copers (n = 17). MAIN OUTCOME MEASURES: The hip, knee, ankle, rearfoot, midfoot, and forefoot kinematic data during the stance phase (0%-100% indicated initial contact to take-off) of a 45° side-cutting task were analysed using one-dimensional statistical parametric mapping. RESULTS: The horizontal plane kinematics of the rearfoot differed significantly among the three groups during 30%-91% of the stance phase (P < .05). Severe-laxity copers exhibited a greater external rotation angle than no-laxity copers during 6%-14% and 32%-92% of the stance phase (P < .05). CONCLUSION: Our data suggest that severe ankle joint laxity affects rearfoot horizontal plane kinematics in individuals without perceived ankle instability performing a 45° side-cutting task. These findings could be used by clinicians in developing rehabilitation programs to prevent further ankle sprains in patients with severe ankle joint laxity.

Determining the relationship between physical status and musculoskeletal injuries in children: a cohort study.

Background: In Japan, in 2016, the School Health and Safety Act was revised and examination of extremities in addition to scoliosis became mandatory. Musculoskeletal examinations were subsequently started using a mark sheet-type questionnaire. In the present study, we aimed to analyze the relationship between physical findings and musculoskeletal problems and propose a preventive strategy for musculoskeletal injuries. Methods: In 2017, a total of 4,073 elementary and middle school students underwent direct musculoskeletal examination. In a direct examination, the following elements were included: torticollis; scoliosis; stiffness of the shoulder, elbow, hip, knee, and ankle; flexion and extension in standing position; flat foot; hallux valgus; and alignment of the upper and lower extremities. Of the 4,073 students who underwent direct examination in early 2017, only 3,754 were able to complete the mark sheet-type questionnaires in early 2018. A prospective longitudinal analysis of the data gathered was performed. Results: A total of 396 (11%) students had injuries. The ankle sprain/non-ankle sprain group comprised 119 (3%)/3,635 (97%) students, while the fracture/non-fracture group comprised 105 (2.8%)/3,650 (97.2%) students, respectively. Comparing the sprain group with the non-sprain group, ankle stiffness significantly correlated with ankle sprain in the univariable and multivariable analyses. Injuries occurred more frequently among boys, older students, students with stiff bodies, and students who were involved in sports activities of longer duration. Conclusion: Ankle stiffness was assumed to be a risk factor for ankle sprain. Stretching of the ankle might be effective for preventing ankle sprain. However, further interventional studies are needed to confirm this finding.

Directions of single-leg landing affect multi-segment foot kinematics and dynamic postural stability in male collegiate soccer athletes.

BACKGROUND: Understanding lower limb kinematics and postural control in different directions of single-leg landings is critical to evaluate postural control and prevent lower limb injuries. However, foot and ankle kinematics and postural control during single-leg landings in different directions are less known. RESEARCH QUESTION: Does the difference in the direction of single-leg landing affect the foot kinematics on the frontal plane and dynamic postural stability? METHODS: A cross-sectional study was conducted. Forty-nine male collegiate soccer players performed single-leg forward (FL), 45° lateral (LL), and medial (ML) direction landings. The lower limb, foot (rearfoot, midfoot, forefoot), and ankle kinematics during an impact phase were evaluated, and a curve analysis was performed using a statistical parametric mapping method to compare the three landings. The three landings were compared in terms of postural control parameters, including time to stabilization (TTS), peak of ground reaction forces (GRFs), root-mean-square of the mediolateral GRFs for 0-0.4 s (GRFML0.4), loading rate, and magnitude of horizontal GRFs from 0-0.4 s (HGRF-0.4), 0.4-2.4 s (HGRF-2.4), and 3.0-5.0 s. RESULTS: Ankle and rearfoot kinematics in LL exhibited smaller eversion and pronation positions than FL and ML (p < 0.01). The TTS-mediolateral (TTS-ML) was longer in the LL than in FL and ML (p < 0.001). The GRFML0.4, HGRF-0.4, and -2.4 in the LL and ML were greater than those in the FL (p < 0.001). SIGNIFICANCE: Directions of single-leg landing affect foot and ankle kinematics and postural stability. Specifically, the LL exhibits more inverted ankle and supinated rearfoot positions, and longer TTS-ML. Thus, the LL may induce stretching of the lateral ankle ligament. These findings can help understand foot kinematics and assess dynamic postural control.

Relationship between early-onset muscle soreness and indirect muscle damage markers and their dynamics after a full marathon.

BACKGROUND/OBJECTIVE: Muscle soreness and damage occurs after completing a full marathon. Here we refer to muscle soreness induced by prolonged running as early-onset muscle soreness (EOMS) because muscle soreness and damage markers induced after prolonged running are different from delayed-onset muscle soreness (DOMS) and muscle damage markers induced after eccentric contraction, such as resistance exercise. The dynamics and relationship between muscle damage markers and EOMS are unclear; therefore, in this study, we aimed to elucidate the relationship between EOMS and indirect muscle damage markers, and their dynamics after a full marathon. METHODS: The following measurements were performed in 19 subjects who completed a full marathon: perceived muscle soreness (using a numeric rating scale), thigh circumference (CIR), hip joint range of motion (ROM), jump height (JH) and muscle damage marker activities in the blood (CK, AST, LDH, ALD) before (Pre), after (Post) and every day for 4 days after a full marathon (D1-4). RESULTS: EOMS was induced, as determined by the numeric rating scale score peaking immediately after a full marathon. ROM and JH significantly decreased and all muscle damage markers significantly increased after a full marathon. Serum CK and AST peaked at D1. Serum LDH and ALD peaked at Post and D3. Each marker showed different dynamics. CIR significantly decreased after a full marathon. CONCLUSION: Muscle soreness peaked and muscle damage markers in the blood showed different dynamics after a full marathon. In other words, this is different from DOMS.

Ten-year results of 55 dysplasia hips of hip offset and leg length reconstruction in total hip arthroplasty with cementless tapered stems having a high offset option designed for dysplastic femur.

PURPOSE: In developmental dysplasia of the hip (DDH), the centers of hip rotation move in the superior and lateral direction. In total hip arthroplasty for such cases, movement of the center of hip rotation is in the inferior and medial direction. It causes an increase in leg length and a decrease in acetabular offset. We therefore evaluated the change of hip offset and leg length before and after surgery with two stems having a high offset option. PATIENTS AND METHODS: The preoperative diagnosis was secondary osteoarthritis due to DDH excluded Crowe IV. A stem selection was decided based on preoperative two-dimensional templating. Total 55 hips in 50 patients were followed up for minimum 10 years. Pre- and postoperative clinical evaluations were performed using a hip joint function scoring system. Radiographic evaluations were used for offset and leg length measurements and other associated factors. RESULTS: Both stems showed excellent clinical results. A high offset option was used in 60% of all cases. No postoperative dislocations were observed. The biological fixation was stable in all cases. The hip offset was restored without excessive leg lengthening in most cases. CONCLUSION: Anatomical consistency could be maintained by using a stem which matched geometry of the proximal part and had offset option. These cementless tapered stems having a high offset option are suitable for Crowe I to III hip dysplasia if two-dimensional X-ray templates fit the shape of the proximal femurs. They were associated with excellent clinical results and biological fixation. The offset option may be useful to adjust leg length and offset in DDH patients.

Sex Differences in Iliotibial Band Strain under Different Knee Alignments.

BACKGROUND: Increased strain of the iliotibial band (ITB) is a plausible contributing factor for the development of iliotibial band syndrome (ITBS). Although several studies have found relationships between the strain of the ITB and kinematic factors during running, the associations of the ITB strain with knee alignment and sex, which are considered intrinsic factors, are not well understood. OBJECTIVE: To clarify the sex differences in the ITB strain between genu varum and normal knee alignments in different postures. DESIGN: Observational cross-sectional study. SETTING: Laboratory research within a university. PARTICIPANTS: Forty-four healthy recreational athletes (21 men and 23 women) volunteered for this study and were divided into four groups by sex and knee alignment: men with genu varum alignment, men with normal knee alignment, women with genu varum alignment, and women with normal knee alignment. METHODS: An ultrasound real-time elastography (RTE) unit was used for distal ITB strain measurements in weight bearing and for different non-weight-bearing: neutral, knee flexion, hip adduction, and hip adduction with knee flexion. Gender information and the intercondylar distance data were collected to divide the participants into two groups. MAIN OUTCOME MEASUREMENTS: Main Outcome was the ITB strain (strain ratio) measured by the RTE. RESULTS: There were no significant differences in neutral and hip adduction postures among the four groups. However, during weight-bearing, the women's genu varum group (6.91 ± 1.69; Mean ± SD) exhibited greater strain than both the men's normal group (3.50 ± 1.04, P = .005) and the women's normal group (4.42 ± 1.42, P = .048). In addition, there were significant positive correlations between the intercondylar distance and the ITB strain during weight-bearing (r = 0.315, P = .037). CONCLUSIONS: The women's genu varum group exhibited a higher ITB strain during weight-bearing, which may be related to the high incidence of ITBS in women athletes. Furthermore, the changes in alignment and muscle activities during weight-bearing could influence the strain of the ITB. LEVEL OF EVIDENCE: III.

Characteristics and factors of concussion events for tacklers in collegiate rugby union.

The purpose of this study was to determine the factors related to the occurrence of concussion in rugby tacklers. Match video records showing tackles leading to concussion were used to identify injury-inciting events. Additionally, noninjury tackles by concussed tacklers (prior to concussion) and position-matched tacklers from the same matches were used as a control cohort. All tackles were coded according to the tackling characteristics. The odds ratio (OR) was reported by logistic regression. The results demonstrated that a side step of the ball-carrier reduced the risk of concussion for tacklers (OR = 0.13 [95% CI, 0.03-0.58]; P = .008). Conversely, the tackler's head/neck contacting the ball-carrier (OR = 18.62 [95% CI, 4.59-75.49]; P < .001) and not remaining bound to the ball-carrier since making initial contact (OR = 4.38 [95% CI, 1.69-11.34]; P = .002) were identified as risk factors for the concussion of tacklers. These results suggest that avoidance movements of the ball-carrier prior to tackling reduced the risk of concussion and that incorrect tackling techniques contributed to an increased occurrence of concussion. Furthermore, the probability of concussion for tacklers increased when their head was in front or to one side of the ball-carrier, and the direction of the tackle also affected the risk of concussion, especially from the side. Therefore, it is important to emphasize the tackler's head position in conjunction with the direction of tackle.

Relationship between exercise time and musculoskeletal problems in children.

Objectives: The purpose of this study was to evaluate the relationship between exercise time and musculoskeletal problems and to determine the appropriate amount of exercise for children in both lower- and higher-grade levels of elementary and junior high schools. Materials and Methods: Mark-sheet-type questionnaires were distributed to and collected from all elementary and junior high schools in two cities. We collected 22,494 questionnaires in total. The relationship between exercise time and musculoskeletal problems was analyzed. The χ2 test and multivariate logistic regression analysis were used for statistical analyses. Results: The mean exercise time in school, in addition to physical education time, was 3.1 hours per week. In 56% of the children, the exercise time was less than 2 hours per week, and in 13% of the children, the exercise time was more than 10 hours per week. Although the rate of sports injury increased with an increase in exercise time, the duration of one-leg stand (a test of balance and muscle strength) also increased with an increase in exercise time. The cut-off values for sports injuries in boys/girls were 2.9/2.9 hours, 4.0/2.9 hours, and 7.5/4.2 hours in lower grade elementary school, higher grade elementary school, and junior high school, respectively. Conclusions: Although an appropriate amount of exercise improves one's physical health and ability, excessive exercise leads to musculoskeletal problems. Approximately 7 hours/week of exercise is recommended for junior high school students. In elementary school, the exercise time should be carefully decided as the musculoskeletal system of the students is still immature.

Prophylactic pinning should be considered in patients at risk for slipped capital femoral epiphysis.

Background: The use of prophylactic contralateral pinning for slipped capital femoral epiphysis (SCFE) remains controversial. This study evaluated the outcome of SCFE treatment and examined the use of prophylactic pinning. Methods: The study included 44 patients (33 men, 11 women; 54 hips [right, 31; left, 23]), with mean age of 12.9 (7.3-29) years, who underwent treatment between 1986 and 2017, with follow-up for more than 6 months. Patients were divided into 3 groups: group 1 had bilateral SCFE at first presentation, group 2 developed contralateral side SCFE during follow-up, and group 3 had unilateral SCFE until final follow-up. Three patients who received prophylactic pinning were excluded. Univariate and multivariate logistic analyses were performed. Results: Overall, 93% (50/54) of hips underwent positional reduction and in situ fixation and 7.4% (4/54) underwent open reduction. Mean follow-up period was 4.8 (0.5-25) years. Groups 1, 2, and 3 had 7, 3, and 31 cases, respectively. Sex, age, and follow-up period showed no significant differences among the groups. The Rohrer index was significantly higher in group 1, the affected side posterior sloping angle (PSA) was significantly higher in group 3, and the contralateral side PSA and percentage with endocrinopathy were significantly higher in group 2. In multivariate logistic analysis, age, sex, Rohrer index, affected side PSA, and endocrinopathy were significantly correlated with bilateral SCFE. Conclusion: We recommend prophylactic contralateral side pinning in patients with risk factors of obesity, high PSA before slipping, and endocrinopathy. Careful observation until growth plate closure is required in patients without risk factors.