Finger injuries may be caused by the way a hold is grasped during sports climbing. We investigated the relationship between the flexion angle of the proximal interphalangeal (PIP) joints of the middle and ring fin ger and finger disorders. The subjects were 104 hands of 52 contestants in the Chiba Prefecture Bouldering Youth Championship in April 2016. Eighteen contestants (34.6%) suffered hand injuries at a total of 38 locations including 76.3% of the middle and ring fingers and 42.1% of the PIP joints. It is possible that finger disorders are caused by a greater degree of flexion of the middle and ring finger PIP joints as competition increases and the number of diffi cult tasks, including obstacles, increases. It is suggested that PIP joint failure is caused by hyper flexing of the PIP joints or forcing the joints to bend too far sidewards due inadequate instructions to beginner climbers.

This study is focused on the prevention of tendon elongation during the non-operative treatment of Achilles tendon rupture. We studied the MRI, US and clinical findings of 120 patients treated at our hospital. The items examined are change in elasticity between the tendon stumps on dynamic US, dynamic MRI, elastic modu lus, volume, and length. The US-based Thompson test, the appearance of a negative Thompson test and disappear ance of mechanical elasticity on dynamic US are achieved by 4 weeks and are closely connected to each other.When the difference in elasticity between the tendon stumps diminished, the dynamic MRI did not show elonga tion between the tendon stumps, suggesting that ankle movement could be started safely at that time. It was sug gested that separation between the tendon stumps did not occur, even if load and automatic movement of the an kle joint were performed 3-4 weeks after the initial fixation. This study suggests the importance of the prevention of tendon stump detachment within 3 to 4 weeks after initial fixation in case of non-operative treatment of Achilles tendon rupture.

This study analyzed how long-term exercise suspension due to COVID-19 affected the occurrence of injuries in official post-suspension Japanese collegiate American football games in 2020. Injury report data submitted by Kantoh Collegiate Football Association were analyzed and compared between A (2020) and B (1991-2010, 20years). We analyzed the number of cases of injury per match, trauma classification, trauma by body part, and trauma name. The injury incidence rate was A: 2.34 and B: 1.33 cases/match; trauma classification included bruises/contusions (A: 32.4%, B: 16.7%) and fractures (A: 9.0%, B: 2.4%); body parts included the lower leg (A: 14.5%,B: 7.8%) and thigh (A: 9.0%, B: 4.9%); and trauma diagnosis included lower-leg muscle spasm (A: 8.3%, B: 2.9%) and thigh bruises (including muscle pulls) (A: 8.3%, B: 4.0%). All were significantly higher in A (p＜0.05). We considered these factors to be due to decreased lower-limb joint flexibility caused by long-term inactivity and excessive load on muscles and tendons of the lower legs and thighs due to movements such as dashing, stopping, cutting, and turning. One cause of the increase in fractures may be the inability to avoid injury due to decreased bone strength or decreased skill due to inadequate actual practice.

The purpose of this study was to investigate the relationships between the single-leg standing-up test（SLST）, hip/knee flexion angles during single-leg landing and knee muscle strength. Sixty-five subjects with out any orthopaedic symptoms were included in the study. The subjects were classified into higher and lower SLST ability groups depending on whether they could perform SLST from the 20cm level. For the kinematic analysis of landing, single-leg landing motion from a 30cm high platform was videotaped from the lateral side.Markers were attached to bony landmarks in the pelvis and lower limbs, and knee and hip flexion angles were measured on the video image. Isometric knee extensor and flexor strength were also evaluated. During the data analysis, the obtained results were compared between the groups. The comparative analyses showed that the hip and knee flexion angles on landing were significantly larger and the knee flexor strength was significantly greater in the group exhibiting higher SLST ability. These results suggest that larger hip and knee joint flexion angles on single-leg landing and higher knee flexor strength are associated with superior performance in the SLST.

We aimed to determine droplet and aerosol concentrations during interval exercise using an aero bike. The participants were 39 healthy university students. Using Power Max V3, an anaerobic power test was performed in the first stage to determine the load used for middle power training. In the second stage, the determined load amount was used for 30 s each for two sets of full-power pedaling. A particle counter was used to measure the exhaled droplets and aerosol during the interval exercise.

The results showed an increase in particles with a diameter of 0.3 to < 0.5 μm and 0.5 to < 1.0 μm with the start of movement, and a tendency of the particle size to constantly increase during exercise. Particles with a diameter of 1.0 to < 2.0 and 2.0 to < 5.0 μm peaked under exercise load and decreased with exercise cessation. For particles with a diameter of 1.0 to < 2.0 μm and 2.0 to < 5.0 μm, there was a significant difference between the particle concentrations at the peak and exercise cessation.

During exercise, aerosols in the exhaled air showed different dynamics depending on the particle size. Infectionprevention measures during sport activities should therefore be designed according to the particle size of the aerosols or droplets that are emitted during different stages of exercising.

The objective of this study was to investigate the sports-related injuries that occurred immediately after resuming sports after activities had been suspended due to COVID-19. Athletes aged from 10 to 18 years old who visited our medical center in June and July 2020 or June and July 2019 were included. During the self exercising period, most athletes performed exercises amounting to half or less the normal amount of activity.About 30% of athletes had also gained weight. The experience as athletes who visited our institution in 2020 was significantly longer than those who visited in 2019. The lower leg, including the knee, foot and ankle, was the most common site of injury of junior athletes in this study. The rate of contact injuries in junior high school athletes was decreased in 2020 compared with that in 2019. There were significant differences concerning the future goal as an athlete among high school athletes. The recreational level (8 athletes, 34.8%) was increased and coaching staff (0 athletes, 0%) was decreased in 2020. These results suggested that mental and social support of junior athletes were also important during activity restrictions due to the spread of COVID-19 infection.

The purpose of this study is to understand the features and circumstances of anterior cruciate ligament (ACL) injuries male soccer players sustained Japanese professional (J-League) matches. The participants were J-League players from various clubs and were followed for four playing seasons, from 2016 to 2019. There were 111 cases of ACL injuries that were officially announced. Of these 111, we could confirm 42 by video. The items examined were the number of occurrences in each case, namely, (1) the injury form (non-contact / contact injury), (2) offensive/defensive, (3) movement direction (forward / backward with respect to the attack direction),and (4) injury area (offensive/defensive area). We also compared the rates of occurrence of the injured area and the direction of movement during attack and defense, and the direction of movement for each injured area during attack and defense, respectively. The results tended to be higher for more non-contact and defensive cases.

In the defensive area, the occurrence was significantly higher when moving backwards during defense.

Players should be aware that ACL injury prevention is important in high-intensity defensive play, and that there is a high risk of injury, especially when moving backwards in the defensive area.

(Background) As lumbar lordosis and anterior pelvic tilt are associated with lumbar spondylolysis,we attempted to correct the lumbar alignment of patients with fresh lumbar spondylolysis by applying physical therapy (PT). We investigated the change in lumbar and pelvic alignment resulting from our PT program.

(Materials and Methods) We retrospectively evaluated 76 children aged 7-17 years with fresh lumbar spondylosis.We measured lumbar lordosis (LL) and the sacral slope (SS) on the radiographs taken at the first visit and after pain improvement. The PT group comprised patients who had undergone the PT program.

(Results) LL was 48±10̊(PT group) and 51±11̊(control group) at the first visit (p=0.172), and 49±9̊and 54±10̊later (p=0.007), respectively. The SS was 37±7̊and38±10̊(p=0.180) at the first visit, and 36±7̊and 41±10̊(p =0.008) later in the PT and control groups, respectively. Both LL and SS in the control group were significantly increased (p=0.008 respectively).

(Conclusion) This study suggests that PT may improve lumbar spine alignment and the recurrence of lumbar spondylolysis in patients with fresh lumbar spondylolysis.

Many cases of sudden death have been reported during triathlon competitions, and most frequently occur during the swimming part. However, measures to reduce the risk of sudden death are unknown. We conducted a cross-sectional study to explore the risk factors of athletes who used the first aid station and retired during triathlon competitions in 2014. A questionnaire survey on the condition of participants was conducted on the day before the event. Those who used the first aid station and retired from the competition were defined as the “event group.”The Mann-Whitney U test and the χ-square test were used for analysis. Alcohol consumption on the day before the event was also surveyed. The number of participants was 718; nine were classified into the event group, and seven of them retired during the swimming part. Those in the swimming part event group (p＜0.05), had practiced less in an open water swimming situation (OWS) and had shorter experience of OWS (p=0.06).One case, who was transported by ambulance, had drunk sixty grams of alcohol the previous night. A relatively low frequency and experience of OWS could be a risk factor for athletes who used the first aid station and retired during triathlon competition. Alcohol consumption the previous night may also be a risk factor.

In this study, we focused on “limitation of standing forward flexion”in a musculoskeletal examination,followed the results of the examination for six years, and examined the characteristics of individual developmental status of elementary school students.

Thirty-nine children with six-year records of musculoskeletal examinations and growth data of one public elementary school in Ibaraki Prefecture were examined. The height growth velocity curve was drawn based on the individual height data, and the age at take-off, and the peak velocity was confirmed. We assigned children to the “emergence group”if they had “limitation of standing forward flexion”at least once in six years of those who had no findings in the first grade.

There were 19 boys and 12 girls who did not have “limitation of standing forward flexion”in the first grade.

When the records of this group were followed up for six years, nine boys and three girls later presented with this finding. Four out of nine boys presented with this finding at an age of take-off±1.0 years. It is necessary to conduct multivariate analysis that includes various factors such as exercise habits and physical fitness to properly understand the musculoskeletal system of children.

A total of 1149 high school or younger patients who visited our clinic due to low back pain and underwent MRI were included in this study. They were divided into two groups, namely, with and without fresh lumbar spondylolysis. The evaluation items were pain provocation tests (flexion pain, extension pain, and the Kemp test),gender, age, sports event, and duration from symptom onset to consultation.

There were no differences in the positivity rate of each pain provocation test between the two groups of with and without spondylolysis. The proportion of males with spondylolysis was significantly higher than those without spondylolysis (p＜0.01). The proportion of junior high school students with spondylolysis was significantly higher than those without spondylolysis. The proportion of high school students with spondylolysis was significantly lower than those without spondylolysis (p＜0.01). The sports events in which patients with spondylolysis exceeded those without spondylolysis were soccer, baseball, track and field, and handball. The results of this study suggest that it is necessary to conduct MRI of males, junior high school students, and those who play soccer, baseball, track and field, and handball to make a differential diagnosis of fresh lumbar spondylolysis.

The present study examined whether sideways bench training can serve as a simple method for assessing hip abduction muscle strength. In Study 1, which was conducted in 124 high school to adult basketball players, we examined hip abduction torque relative to body mass (HAT/BM) and the number of sideways bench position repetitions performed in 30 seconds (SB test) as well as the relationship between the two measurements. In Study 2, which was conducted in13 male university students, we measured the relationship between gluteus medius activity and HAT/BM during the SB test using a surface electromyogram. Consequently, we observed a significant positive correlation between HAT/BM and SB test repetitions (r=0.71, P＜0.05; research 1), as well as a significant negative correlation between HAT/BM and gluteus medius activity during the SB test (r=­0.70, P＜0.01; research 2). These results indicate that the SB test may be used as a simple assessment of hip abduction muscle strength.

The side-to-side differences in lower limb kinematics during sport-related activities and self-reported outcome measures in female athletes who returned to play following anterior cruciate ligament reconstruction(RTP-ACLR) are unknown. The purposes of this study were to identify the characteristics of side-to-side differ ences in lower limb joint kinematics during an unanticipated cutting task (UCT), and to measure the knee injury and osteoarthritis outcome score (KOOS) in female athletes following RTP-ACLR. Fifteen competitive female bas ketball athletes who RTP-ACLR participated in this study. Lower limb joint kinematics during the UCT were as sessed using a three-dimensional motion analysis system. KOOS was assessed for subjectsʼknee condition. The injured-side maximal hip flexion angle, knee flexion angle at initial contact and maximal knee flexion angle during the UCT were significantly smaller than on the uninjured side. The KOOS subscales on the injured side were sig nificantly lower than on the uninjured side. Female athletes following RTP-ACLR had reduced hip and knee flex ion angles on the injured side during the UCT, and lower KOOS scores on the injured side compared to the non injured side.

In this study, we investigated the association between lumbar stress fractures (LSF), the acute phase of lumbar spondylolysis, and physical characteristics of adolescent baseball players. Participants were categorized into a fracture group (18 male baseball players aged 12-15 years, diagnosed with magnetic resonance imaging) and a control group (25 asymptomatic baseball players aged 12-16 years). We evaluated the physical examination in both groups using the following tests: finger-floor distance, angle of straight leg raising test, the external and internal range of motion (ER and IR, respectively) of the hip joint, the Duncan-Ely test, the Thomas test, and Oberʼs test. Compared with the control group, the fracture group showed bilateral high positive rates in the Duncan-Ely test, bilateral increase in ER, and bilateral decrease in IR. Tightness of the anterior hip joint may increase the pelvic tilt and a decreased IR may limit pelvic motion during pitching, batting, and dashing, which may exaggerate lumbar load and result in LSF.

Introduction: Mechanical load causes fractures in different directions in case of lumbar spondylolysis. In this study, we compared the angle of the fracture line in lumbar spondylolysis cases between baseball and soccer players.

Methods: We assessed 37 lesions of 34 patients with spondylolysis who were baseball or soccer players and were treated conservatively at our hospital between April 2015 and February 2019. The target vertebral body of this study was only L5. The stage was early or progressive stage on axial CT imaging, and stage 1c or 2 on sagittal CT imaging. Statistical analysis was performed using the t-test, and significance was defined as p< 0.05.

Results: The angle of the fracture line on the axial CT image was 18.7±6.3̊in the baseball group and 19.7±12.2̊in the soccer group (p=0.80), and the angle on the sagittal CT image was 77.3±9.4̊in the baseball group and 66.9±9.5̊in the soccer group (p=0.0064), showing a significantly larger angle in the baseball players.

Conclusions: The angle of the fracture line on the sagittal CT image was significantly greater in baseball than soccer players. This is due to the fact that baseball involves more rotational movement than soccer.

This study assessed age- and sex-specific differences in muscle flexibility and joint laxity in junior competitive swimmers. Of the 452 recruited swimmers aged 10-18 years, 256 were male and 196 were female.Muscle flexibility and joint laxity of the upper and lower extremities were measured using five and seven tests, re spectively. Two-way analysis of variance (age group and sex) was performed. When interaction effects or the main effect by age group was detected, post hoc comparisons were used to test differences between variables by the Tukey-Kramer method. The results showed no significant interaction effects between the tests. Heel Buttock Dis tance (HBD), predominantly reflecting muscle flexibility, and ankle dorsiflexion angle during knee extension indi cated decreased flexibility in older swimmers (p< 0.05). Knee extension angle reflecting joint laxity, indicated in creased laxity in older swimmers (p< 0.05). Shoulder and hip joint internal rotation angles reflecting muscle flexi bility and joint laxity, were decreased in older swimmers (p< 0.05), while toe floor distance (TFD) showed in creased mobility (p< 0.05). Sex differences were observed in shoulder rotation width, distance between middle fin gers, shoulder joint internal and external rotation angles, elbow joint extension angle, hip joint internal rotation an gle, straight leg raising angle, HBD, and TFD (p< 0.05).

The purpose of this study was to explore the relationship between falls and winning and losing in wheelchair basketball games, and to consider the importance of fall prevention. We obtained and analyzed the game videos of the Tokyo 2020 Paralympics wheelchair basketball final tournament. The analysis items included the number of falls, classification of the faller, and the playing time when the falls occurred. We classified the falls into two groups: falls in the winning team and those in the losing team. The number of falls was compared between the winning and losing teams, and the analysis items related to falls were compared between the groups using the chi-square tests and cross-tabulation tables. A total of 326 falls were recorded. Of these, 138 occurred in the winning team and 188 in the losing team. Comparison of items related to the falls between the winning and losing teams showed a significant difference in the classification of the fallers and the playing time (p< 0.05). This study is the first report to examine the relationship between the occurrence of falls in wheelchair basketball and winning or losing a game, and will be useful in raising awareness of fall prevention.

The infraspinatus muscle consists anatomically of transverse and oblique fibers, and the different fi bers have different functions in view of the direction.

The purpose of this study was to evaluate the muscle activity level of the different fibers of the infraspinatus muscle by surface electromyography to determine the function of each fiber type during abduction and external rotation of the glenohumeral joint. The activity of the transverse fibers change during abduction depending on the internal rotation angle of the shoulder joint. The activity of the oblique fibers as related to the transverse fibers changed during shoulder joint abduction movement depending on changes in the shoulder abduction angle. The activity of the respective fibers of the infraspinatus muscle is indicated by differences in shoulder abduction and the internal rotation angle. When we perform functional evaluation and exercise, the function of the respective fi bers of the infraspinatus must be considered.

The authors were aware of shoulder and elbow disorders that collegiate baseball players experienced at the time of enrollment, and researched the characteristics of the medical checkup results of athletes with shoulder and elbow symptoms while at school.

Thirty-seven collegiate hardball baseball players answered questionnaires and underwent ultrasound examination of the shoulders and elbows, and measurement of the ROM of the shoulder and hip joints. The relation with the medical checkup results were investigated in athletes with shoulder and elbow symptoms while at school.

Twenty-six athletes (70.3%) had a history of shoulder and elbow problems.

Abnormal lesions in the rotator cuff were found in thirty-three athletes (89.2%) by ultrasound. In the elbow joints, osteochondritis dissecans of the humeral capitellum was present in four athletes.

Ten athletes (27%) complained of shoulder or elbow pain while at school, including six pitchers and eight experienced pitchers. Although ROM of the shoulder external rotation (2nd position) was increased and shoulder internal rotation (2nd position) on the throwing side was decreased, there was not a statistically significant difference.

One athlete with osteochondritis dissecans, first detected by medical checkup, could be treated early when symptoms developed. We therefore consider that medical checkup at the time of enrollment is useful.

A questionnaire survey of male and female Olympic-style boxers was conducted regarding injuries and the experience of knock out (KO) by a punch to the head. The total number of participants was 650, including 60 female and 590 male boxers. There was a significant difference in injuries between female and male boxers,with male boxers suffering more injuries of the face area (19%), fingers (12%), and hands (11%), due to a direct hit or strike by a punch. Female boxers had fewer injuries than male boxers, with 14% of injuries in the foot, 9% in the knee joint, and 8% in the elbow joint, as well as in areas affected by direct blows. Those that experienced KOs ranged from 34-48% for female boxers and 66-69% for male boxers, with significantly fewer female than male boxers. Symptoms were present after KO in 14% of female boxers and 36% of male boxers, significantly fewer in female than male boxers. Injuries and KOs are less common among female than male boxers in Olympic-style boxing in Japan.

The purpose of this study was to investigate the kinematic characteristics of the thoracolumbar area during trunk extension.

Trunk extension movement was carried out in a standing position under two different conditions by subjects as an experimental task. The first condition was trunk extension from a standing position (free, unfixed condition),and the second was trunk extension with the lower limbs fixed and leaning on a special stable stand, to minimize trunk muscle activity in the maximum extension position (fixed condition). Trunk muscle activity and extension angle from standing to the maximally extended position was measured during the experimental task. The exten sion angle was measured by dividing the thoracolumbar area into six segments, using three-dimensional motion analysis systems.

In the fixed condition, muscle activity of the rectus abdominis muscle was significantly less than that under free,unfixed conditions, and the extension angle was greater in all but the middle-upper and upper-thoracic segments than under the free, unfixed conditions. Under the free, unfixed conditions, the extension angle of the lower lumbar segment was the greatest and the movement of the upper-lumbar segment was greater than that of all other thoracic segments.

This study was intended to investigate functional differences in scapular upward rotation on the thorax among different generations of baseball players with throwing injuries. Forty-two baseball players with throwing injuries and 10 healthy baseball players, who served as controls, were included. The scapular upward rotation movements on the thorax were calculated using the frontal radiography images of the upper extremity in the down and elevated positions. Patients with throwing injuries were classified into two groups: those aged < 15 years (U15 group) and those aged > 16 years (O16 group). Each measured parameter was compared between the U15, O16, and control groups. The upper thorax showed less movement in the O16 and U15 groups than the control group, and less in the former than the latter. Thorax function decreased in cases of throwing injury of high school students and older individuals, suggesting that this may be a physical function that may increase the load on the shoulder and elbow during pitching.

Patellar stress fractures are caused by repetitive quadriceps muscle contractions and patellar tendon-stretching forces on the distal anterior patella. The surgical insertion of a cannulated cancellous screw (CCS) can fix the fracture site and reduce the anterior patellar tendon-stretching forces. This study evaluated the surgical outcome of using CCS for patellar stress fractures in athletes. The surgery was performed on six patients,all female, with an average age of 17.2 years at the time of the surgery. All six cases were sports injuries; four with incomplete fractures and two with complete fractures. The surgery was performed by inserting two CCSs through a small skin incision from the distal side of the patella. The patients started to perform loading and rangeof-motion training soon after surgery, and following bone fusion, resumed their sports activities. In one patient with an incomplete fracture, the CCS passed close to the patellofemoral articular surface, as seen in a lateral radiograph. This prevented the CCS from reducing the anterior patellar tendon-stretching forces, and the patient suffered re-fracture. Osteosynthesis using CCS for patellar stress fractures in athletes shows promising results, serving as a favorable indicator of this procedure. However, the insertion position of CCS should be selected carefully to prevent re-fracture.

The purpose of this meta-analysis was to investigate the evidence for the conservative treatment of patients with acute hamstring injury. MeSH and key words representing acute hamstring injury and conservative treatment were used to conduct an electronic search in PubMed, Central, and ICHUSHI. Randomized controlled trials, controlled clinical trials, and prospective comparative trials investigating the effects of conservative treat ment in patients with acute hamstring injury were included. The main outcomes were the numbers of days to re turn to sports and to re-injury. The quality of included studies was assessed using 12 items related to the risk of bias. Out of 583 studies, six trials met the inclusion criteria for this review. Of these, four studies (208 patients) were included in the meta-analysis to examine the effects of eccentric hamstring exercises and other exercises on the main outcomes. Meta-analysis results suggested that there are no statistical differences between the two treatments on the effect on days to return to sports and re-injury. High heterogeneity was observed. The overall quality of evidence was very low. In conclusion, the number of studies regarding the current topic is limited. It is therefore difficult to determine the true effect of conservative treatment in patients with acute hamstring injury.

Meniscal injury is a common sports-related injury. Although numerous studies about meniscal injury have been reported, only a few studies have been conducted on meniscal injury in soccer players. This study was intended to evaluate the clinical outcomes after meniscal surgery in soccer players.

This was a retrospective study on 33 knees of 32 soccer players who underwent arthroscopic meniscal surgery. All patients were men with a mean age of 19.1 years at the time of surgery. Medial and lateral meniscal injuries were diagnosed in 10 and 23 knees, respectively. The type of medial meniscal injury was a bucket-handle tear from the anterior horn to mid-portion in 9 cases, and a horizontal tear at the posterior horn in one case. Lateral meniscal tears were flap tears in the anterior horn to midbody in 6 cases who underwent partial meniscectomy, while meniscal repair was performed in the remaining cases (17 knees), with or without partial meniscectomy of the lateral meniscus. In terms of return to play, patients who underwent partial meniscectomy and meniscal repair needed 4.3 and 6.2 months, respectively.

The present study demonstrated that longitudinal tears of the anterior horn of the medial and the lateral meniscus are a frequent type of injury.

All patients could return to play and meniscal surgery yielded satisfactory outcomes in soccer players.

The purpose of this study was to investigate the association between the menstrual cycle and the re sults of specific physical fitness tests for soccer players. Twenty-three female collegiate athletes (18 to 22 years) participated in this study. Their menstrual cycle was divided into 3 phases: the menstrual phase, the follicular phase, and the luteal phase. Vertical jump, standing long jump, 30-meter sprint, pro-agility shuttle, and the Yo-Yo Intermittent Recovery Test Level 1 were assessed as fitness tests. The data of 7 participants could be analyzed. No significant differences were observed between the three menstrual phases. However, there was a strong posi tive correlation between the time of the 30-meter sprint (0 to 10 m) and the estradiol levels in the menstrual phase (r = 0.95). There was also a strong negative correlation between the time of the 30-meter sprint (0 to 30 m) and the estradiol levels in the menstrual phase (r = ­0.91), and the progesterone levels in the luteal phase (r = ­0.87). These results suggest that some physical factors in female collegiate soccer players may be affected by specific phases of their menstrual cycle and accompanying hormonal changes.

The need for graduated return to play (GRTP) following recovery from sports-induced concussions has been demonstrated. We report a case of concussion of a collegiate cycling athlete. When returning to daily training and competitions, we set a GRTP program taking cycling competitions and the training environment into consideration. As a result, successful recovery was possible based on the athleteʼs symptoms and degree of recovery. Nonetheless, the results of this study suggested the need to readjust GRTP from the viewpoint of cycling and student sports.

Since bunny hopping (jumping forward in a squatting position) has recently been recognized as a harmful training method, the incidence of proximal fibular stress fractures has decreased. We report a case of bilateral proximal fibular stress fractures due to bunny hopping exercises in a 15-year-old boy belonging to a Kendo club of which the activities were suspended due to the COVID-19 pandemic. Two weeks prior to the first consultation, when club activities resumed after being suspended for 11 months, the patient daily performed bunny hopping exercises. After one week, he developed pain in both lower legs. Plain radiographs showed bilateral proximal fibular stress fractures. After two weeks of treatment with rest, splint fixation of both ankles and lower legs and pain-limited weight-bearing, the tenderness at the fracture sites had almost resolved. Plain radiographs showed callus on both sides; thus, the splints were removed. After four weeks, the patient started running and returned to competitive activities after eight weeks. We should consider bunny hopping as one of the causes of fibular stress fractures after prolonged exercise suspension, such as the COVID-19 pandemic.

Osteochondral lesions, such as Osteochondritis dissecans (OCD) are common in the elbow and knee joints due to overuse in athletes, but are relatively rare at the femoral head of the hip joint.

We have experienced three cases with osteochondral lesions of the femoral head among elite athletes. Two of the three may have been caused by iliopsoas impingement, and the other one was caused by impaction between the femoral head and the acetabulum.

None of these cases had signs of impingement of the hip joint and the lesions were not located in a weight bearing area, and could be successfully treated with conservative methods, and could return to play at the same level as before.

Osteochondral lesions of the femoral head are caused by chronic disorders due to the instability of the pelvic or hip joints. We therefore considered that a comprehensive approach, such as assuring the stability of the hip and pelvis accompanied by kinematic chain training and form check, is necessary for the successful treatment.

We report three cases of quadratus femoris muscle injury caused by ischiofemoral impingement (IFI) in hurdlers.

All cases were teenage women who presented with symptoms on the trail leg side. In all cases, magnetic resonance imaging revealed signal changes in both quadratus femoris muscle bellies. It also revealed narrowing of the bilateral ischiofemoral space (IFS) and quadratus femoris space (QFS) in two cases. However, such narrowing was not noted in the third case, in which knee-in motion of both legs was observed. We consider that hip joint extension of the trail leg in hurdling promotes functional narrowing of IFS and QFS.

We hypothesize that hurdlers with atypical pain in the groin or buttock on the trail leg side may have IFI.

The purpose of this study was to analyze the impact of a short pitching interval of 3 days on throwing motion and ball speed.

The subject was a pitcher who threw a complete game (99 pitches) in the official semifinal baseball game for school-age children, as well as another game (110 pitches) in the final after a pitching interval of 3 days. The method was two-dimensional motion analysis using a high-speed camera.

The results revealed that the pitcherʼs throwing motion and ball speed were generally stable in the semifinal,but markedly worsened from the 51st pitch in the final, which may have allowed the opponent team to score several runs.

The pitcherʼs worsened throwing motions and ball speed suggest that a pitching interval of 3 days is not adequate to for recover from fatigue due to excessive pitching in the semifinal.