PURPOSE: This study aimed to clarify the order of the lumbar maturity stage, each at L1 to L5, and the relationships between age at peak height velocity (APHV) and the lumbar maturity stage. METHODS: A total of 120 male first-grade junior high school soccer players were enrolled and followed for two years, and measurements were performed five times (T1 to T5). The lumbar maturity stage was assessed according to the degree of lesion of the epiphyseal from L1 to L5 using magnetic resonance imaging and classified into three stages: cartilaginous stage, apophyseal stage, and epiphyseal stage. The relationships between T1 and T5 temporal changes and developmental stages divided by 0.5 year increments based on APHV and the lumbar maturity stage at L1 to L5 were examined. For the apophyseal stage, developmental age calculated based on the difference between APHV and chronological age between each lumbar vertebra was compared. RESULTS: We found that part of the cartilaginous stages decreased as time progressed, while that of the apophyseal and epiphyseal stages increased at L1 to L5 (chi-square test, p < 0.01). L5 matured earlier with the apophyseal stage than L1 to L4 (p < 0.05). The lumbar maturity stage was attained toward L1 from L5, comparing different lumbar levels. CONCLUSION: The lumbar maturity stage progresses from L5 toward L1, and the apophyseal and epiphyseal stages would replace the cartilaginous stage at approximately 14 years of age or after APHV.

BACKGROUND: Lumbar bone stress injury (BSI) is a high-risk long time-loss injury for adolescent soccer players. However, the risk factors for lumbar BSI are unclear. PURPOSE: To identify the risk factors for bilateral lumbar BSI for adolescent soccer players. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Adolescent soccer players underwent orthopaedic examination, whole-body dual energy x-ray scan, lumbar magnetic resonance imaging (MRI), and muscle tightness testing at baseline. Lumbar lordosis (LL), sacral slope, maturity stage of lumbar vertebral body, and bone marrow edema (BME) at the L5 were examined via MRI. In addition, bone mineral density and content; trunk lean body mass via dual energy x-ray scan; and bilateral muscle tightness including the iliopsoas, hamstrings, and quadriceps were measured. Lumbar BSI was diagnosed as positive bilateral BME and extension-based lumbar pain. All participants were examined twice, one at 6 months and one at 1 year, after the baseline examination. Multivariate logistic regression analysis was performed to identify the risk factors for bilateral lumbar BSI. RESULTS: A total of 69 (26.3%) players were diagnosed with bilateral lumbar BSI. Asymptomatic BME (odds ratio [OR], 4.260; 95% CI, 2.153-8.431), apophyseal stage of the lumbar vertebral body (OR, 3.438; 95% CI, 1.698-6.959), sacral slope relative to LL ≥5° (OR, 4.067; 95% CI, 2.021-8.181), and hamstring tightness ≥50° (OR, 3.221; 95% CI, 1.385-7.489) were significantly associated with bilateral lumbar BSI. CONCLUSION: The incidence of bilateral lumbar BSI was common at 26.2%. Asymptomatic BME, sacral anterior tilt relative to LL, immature lumbar epiphyses, and hamstring tightness were found to be risk factors for bilateral lumbar BSI. The results of this study suggest that regular MRI examination could facilitate the early detection of BME, and improvement in hamstring flexibility and lumbosacral alignment may prevent bilateral lumbar BSI in young athletes.

BACKGROUND: Lumbar spondylolysis (LS) is a common cause of low back injury in adolescent athletes; however, little is known about the relationship between trunk muscle morphology, lumbopelvic control, and LS. This study aimed to clarify trunk muscle morphology and clinical test characteristics in adolescent male soccer players with unilateral lumbar spondylolysis (uni-LS). METHODS: In total, 19 of the 107 adolescent male soccer players were enrolled and categorized into a uni-LS group, based on magnetic resonance imaging (MRI), and an age-, height-, and weight-matched control group. MRI-derived cross-sectional areas (CSAs) of the L4/5 vertebrae were extracted, and the psoas major (PM), multifidus (MF), and erector spinae (ES) muscles were analyzed. Active straight leg raise (ASLR) and hip extension (HE) tests were performed, and lumbopelvic depression was evaluated. Two-way analysis of variance was applied to determine trunk muscle CSA differences between groups, and the two-sided Fisher's exact test was employed to evaluate the association between uni-LS and clinical findings. RESULTS: A significant main effect [F (1,35) = 15.1, p < 0.001] and interaction effect [F (1,35) = 4.1, p = 0.047] were found in the PM, indicating a smaller PM on the LS side in the uni-LS group. A significant association was also observed between uni-LS and ASLR on the LS side, with 13 of 16 players (81.2%) showing positive ASLR corresponding to the uni-LS group (p = 0.003). CONCLUSION: A smaller PM and lumbopelvic depression during ASLR on the LS side characterize adolescent soccer players with uni-LS. These findings may provide useful information to help clinicians understand potential characteristics of uni-LS.

OBJECTIVE: This study aimed to investigate the foot morphology, flexibility of foot and ankle joints, and cross-sectional areas of intrinsic and extrinsic foot muscles in competitive swimmers. METHODS: This study included 18 male university swimmers (swimmer group) and 12 healthy male participants (control group). RESULTS: The swimmer group exhibited greater foot and ankle joint flexibility, less ankle dorsiflexion range of motion, lower toe-floor distance values, and larger foot circumference and width. The cross-sectional areas of the abductor hallucis, tibialis posterior, flexor pollicis longus, and extensor digitorum longus muscles were larger in the swimmer group than in the control group. CONCLUSION: Kicking motion during ankle plantarflexion, especially the plantarflexors of the ankle joint, may lead to the development of intrinsic foot and extrinsic ankle muscles.

Background

Foot strike patterns during running are typically categorized into two types: non-rearfoot strike (NRFS) and rearfoot strike (RFS), or as three distinct types: forefoot strike (FFS), midfoot strike (MFS), and RFS, based on which part of the foot lands first. Various methods, including two-dimensional (2D) visual-based methods and three-dimensional (3D) motion capture-based methods utilizing parameters such as the strike index (SI) or strike angle (SA), have been employed to assess these patterns. However, the consistency between the results obtained from each method remains debatable.

Hypothesis/Purpose

The purpose of this study was to examine the agreement for assessing foot strike patterns into two (NRFS and RFS) or three types (FFS, MFS, and RFS) between 2D visual- and 3D motion capture-based methods. The authors hypothesized that using two description types (NRFS and RFS) would have high inter-method reliability; however, using three description types (FFS, MFS and RFS) would have lower inter-method reliability because of the difficulty in distinguishing between FFS and MFS.

Study design

Controlled Laboratory Study

Methods

Overall, 162 foot strikes from four healthy runners with various foot strike patterns were analyzed. Running kinematics and kinetics were recorded using a 3D motion capture system with a force platform. Each foot strike was filmed at 240 fps from the sagittal perspective. The visual, SI, and SA methods were used, and the kappa values for each method were calculated.

Results

An assessment of the two types of foot strike: NRFS and RFS, revealed almost perfect kappa values (κ = 0.89–0.95) among the visual, SI, and SA methods. In contrast, an assessment of the three types: FFS, MFS, and RFS, revealed relatively low kappa values (κ = 0.58–0.71). Kappa values within the NRFS category, which includes MFS and FFS, ranged from fair to slight (κ = 0.08–0.33).

Conclusion

Previous laboratory findings that categorized foot strike patterns into two distinct types may be applied in observational studies, clinical practice, and training situations.

Level of evidence

Level 2

This study aimed to determine the influence of sport type and training volume during adolescence on low bone mineral density (BMD) in long-distance runners. In total, 125 competitive long-distance runners (64 males; 21.3±4.2 years, 61 females; 21.4±3.1 years) participated in this retrospective cohort study. We collected training history data during adolescence using a questionnaire and measured BMD of the lumbar spine and whole body using dual-energy X-ray absorptiometry (DXA). Male runners with low BMD ran for more hours (p=0.02) and had a smaller proportion of multidirectional loading activity (p=0.03) in elementary school than those with normal BMD. Although female runners with low BMD performed multidirectional activity for more hours in middle school than those with normal BMD (p=0.01), running volume was similar between groups. There was an increasing trend in the total number of hours of physical activity in middle school in female runners with low BMD (p=0.05). These results suggest that avoiding specialization in long-distance running, increasing the proportion of multidirectional sports, and preventing overload during the bone growth phase may reduce the risk of low BMD among runners.

BACKGROUND: Calcaneal apophysitis is the most common cause of heel pain in children and adolescents. However, the relationship between skeletal maturity and heel pain in the specific youth cohort is unclear. PURPOSE: To clarify the relationship between the maturity stages of the calcaneal apophysis and heel pain in youth baseball players. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 336 youth male baseball players participated in this study. Ultrasound scanning of the calcaneal apophysis was performed along the longitudinal line connecting the middle of the Achilles tendon, the middle of the calcaneus, and the second toe, between the proximal calcaneal edge and the medial calcaneal tubercle. The authors classified the maturity of the calcaneal apophysis into 5 stages, from nonpresence of the apophysis (stage 1) to complete fusion (stage 5). The diagnosis of heel pain was based on subjective report of feeling pain on the squeeze test. The relationship between the maturity stages and physical characteristics was investigated using 1-way analysis of variance or the Kruskal-Wallis test, and the relationship between the maturity stages and heel pain was investigated using the chi-square test. RESULTS: Of the 336 players, 49 had heel pain, for a prevalence of 14.6%. Eighteen (5.4%) players had unilateral heel pain, and 31 (9.2%) players had bilateral heel pain. There were no significant differences in the maturity stages of the calcaneal apophysis between the players with no heel pain and those with heel pain. However, no players had heel pain during stage 5, when the calcaneus had completed its maturation. CONCLUSION: The prevalence of heel pain was 14.6% in Japanese youth male baseball players. There was no relationship between the maturity stages of the calcaneal apophysis and heel pain. Heel pain that could be associated with calcaneal apophysitis did not occur during stage 5, when maturation of the calcaneal apophysis was complete.

BACKGROUND: The purpose of this study was to clarify the differences in the movement of the superficial microchambers and deep macrochambers of the heel fat pad during loading and unloading movements, and to clarify the influence of height and weight on this movement. METHODS: The subjects were 21 healthy adults. The right foot was placed on an evaluation instrument stand made of polymethylpentene (PMP) resin plate, and the left foot was placed on a scale stand used to adjust the amount of load. When measuring, the heel fat pad is divided into the superficial microchamber layer and the deep macrochamber layer, and the thickness due to loading from 0% to 100% of the body weight and unloading from 100% to 0% is measured. Measurement was performed every 20% using an ultrasound imaging device. We also examined the rate of change in the thickness of the superficial and deep layers of the heel fat pad when applying 100% load (end load) from 0% load (unload). RESULTS: No changes were observed in the superficial layer of the heel fat pad during unloading, but significant changes were observed in the deeper layers. Additionally, the thickness of the microchamber and macrochamber layers tended to increase under each loading condition as the height and weight increased. On the other hand, the rate of change in the thickness of the macrochamber layer tended to decrease. CONCLUSION: The microchamber layer and the macrochamber layer of the heel fat pad may have different functions. As height and weight increase, the thickness of the microchamber and macrochamber layers may increase, and the rate of change in the thickness of the macrochamber layer appears to decrease. Although the thickness increases as the load increases, we found that the related elasticity decreases. LEVEL OF EVIDENCE: Level Ⅳ, cross-sectional survey study.

BACKGROUND: This study aimed to investigate the thickness changes of the heel fat pad and the plantar fascia associated with loading and unloading in healthy individuals and patients with heel pain and reveal the differences between them. METHODS: The study included adult male participants with (n = 9) and without (n = 26) heel pain. The participants placed their right foot on an evaluation apparatus with a polymethylpentene resin board (PMP), while their left foot was positioned on a weighing scale used to adjust the loading weight. The heel fat pad was differentiated into superficial Microchamber and deep Macrochamber layers. These layers and plantar fascia thickness were measured using an ultrasonographic imaging device at loading phase ranging from 0% to 100% of their body weight and unloading phase from 100% to 0%. Additionally, the study examined the thickness change ratios of the superficial and deep heel fat pad layers when the load increased from 0% (unload) to 100% (full load). RESULTS: In healthy individuals and patients with heel pain, no significant thickness changes were observed in the Microchamber layer of the heel fat pad or the plantar fascia during loading and unloading evaluations. However, significant thickness changes were observed in the Macrochamber layer of the heel fat pad, and the pattern of change differed between the loading and unloading phases. Additionally, patients with heel pain showed differences in the thickness change and thickness change ratios of the microchamber and macrochamber layers of the heel fat pad during both loading and unloading phases. The thickness of the plantar fascia did not show significant differences between both groups. CONCLUSION: Compared with healthy individuals, in our relatively small study, patients with heel pain had greater deep fat pad compression in loading and less recovery after load removal. This finding suggests that these patients have different intrinsic fat pad function and related morphology than those without heel pain. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

BACKGROUND: Low-frequency acupuncture is used to maintain skeletal muscle flexibility and improve joint range of motion; however, its definite effects are unclear. This study aimed to determine the effects of low-frequency acupuncture on muscle and fascial stiffness and ankle dorsiflexion range of motion. METHODS: The participants included 12 randomly selected healthy adults. The medial head of the gastrocnemius muscle was selected as the target muscle, and changes in hardness and dorsiflexion range of motion of the ankle joint in the deep fascia, muscle, and deep intermuscular fascia of the same region were measured before and after low-frequency acupuncture intervention. Acupuncture needles were inserted until they passed through the deep intermuscular fascia and electrically stimulated at a frequency of 2 Hz for 15 min. The 12 right legs were the intervention legs, and the 12 left legs were the non-intervention legs. RESULTS: In the intervention leg, hardness increased in the deep fascia immediately after low-frequency acupuncture, but decreased in all regions (deep fascia, muscle, and deep intermuscular fascia) after 15 min. The rate of change in hardness was the greatest in the muscles and deep intermuscular fascia. Additionally, the ankle's dorsiflexion range of motion increased after 15 min. In contrast, the non-intervention leg showed no significant changes in stiffness or ankle dorsiflexion angle. CONCLUSIONS: Low-frequency acupuncture may decrease muscle stiffness and improve fascial gliding. The change in hardness tended to be greater in the deeper areas.

Abstract

Background

Identifying the characteristics of batting mechanics, such as the proper angle and position of each body segment in youth baseball players, is important for proper instructions. This study aimed to identify the age-related changes in batting kinematics including rotational and separational movements of the head, upper trunk, pelvis, and arms, in youth baseball players.

Methods

Over the three seasons, we measured the batting motion of baseball players aged 6- to 12 years using three high-speed cameras. Participants were divided into six age categories according to the little league eligibility rules (players were classified according to their age as of July 31 of a given year). Toss batting was performed using an automatic tossing machine set obliquely in front of the batter. Additionally, we analyzed the rotation angles of the head, upper trunk, pelvis, and arm direction, and the separation angles—calculated using the difference of each rotational angle and the head movement distance and step width—at five points in batting phase: stance, load, foot contact, pre-swing, and ball contact. Finally, 17 players from under 8 (U8, i.e., approximately 7–8 years) to U10 and 13 from U11 to U13 were analyzed. A one-way repeated measures analysis of variance was performed to analyze age-related changes in batting kinematics.

Results

Several age-related changes in batting kinematics at various batting point were observed. The head-to-upper trunk separation angle increased with age from U8 to U10 during the foot contact (effect sizes [ES] = 0.658) and from U11 to U13 during the pre-swing (ES = 0.630). Additionally, the U13 showed a significantly increase in the upper and pelvis separation angles during load, foot contact, and pre–swing compared with U11 and U12 (ES = 0.131, 0.793, and 0.480).

Conclusion

Various changes in batting kinematics occurred among each age group. Notably, U12 and U13 had the greater upper trunk-to-pelvis separation angle at foot contact and pre-swing compared to U11. Therefore, it would be important for the instruction of younger baseball players to understand the underdevelopment of trunk separation when batting and encourage the acquisition of such separation movements.

BACKGROUND: Risk factors for throwing injuries related to pitching mechanics are unknown. Insufficient pelvic rotation during pitching may be a risk factor for shoulder and elbow injury. HYPOTHESIS: This cohort study aimed to identify biomechanics risk factors for throwing injuries in young baseball players. We hypothesized that excessive mechanical load and motion errors would be risk factors for throwing injuries. METHODS: Young baseball pitchers (aged 8-9 years) were recruited from regional baseball leagues between December 2016 and December 2019. Pitching measurements were performed before the start of each season and after the end of the last season in December 2019. The trunk tilt angular displacement, pelvic rotation angular displacement, and forearm rotation angle were calculated using a markerless motion capture system. We also measured elbow varus torque using an accelerometer. After the initial test session, each participant was followed-up for 3 years to determine the occurrence of throwing injuries. Players with throwing shoulder and elbow injuries were categorized into the throwing injury group, and those without shoulder and elbow pain for 3 years were categorized into the non-injured group. RESULTS: In this study, 97 baseball pitchers completed a 3-year follow-up. Among those participants, 66 (68.0%) had throwing injuries. A significant difference was observed between the throwing injury and non-injured groups, whereby the injured players had less pelvic rotation angular displacement. CONCLUSION: Insufficient pelvic rotation during pitching is a newly discovered risk factor related to throwing injuries.

(目的)Magnetic resonance imaging(MRI)を用いた仙骨傾斜角評価を基準とし,傾斜計を用いた腰仙椎角の計測の精度を検証とすること,予測回帰式を探索することを目的とした.(方法)中学生の男子70名を対象とし,腰部のMR撮像および傾斜計を用いた腰仙椎アライメント測定を実施した.得られたMR画像から脊柱の正中矢状断を抽出し,仙骨の上縁と画像の水平線をなす角を仙骨傾斜角として算出した.また,腰仙椎角の測定には傾斜計を用い,腰仙椎部に傾斜計の0°の軸が通る位置で計測を行った.そしてBland-Altmanプロットを用いた両測定法の一致度の検証に加え,MR撮像による仙骨傾斜角と傾斜計による腰仙椎角との関係を線形回帰分析によって検討した.(結果)MRIを用いた仙骨傾斜角と傾斜計による腰仙椎角との差で求められる固定誤差は10.06±3.29°を示した一方で,比較誤差および偶然誤差は小さかった.MRIを用いた仙骨傾斜角と傾斜計による腰仙椎角との間には有意な関連が見られ,予測回帰式はy=0.85x+13.49が得られた.(結論)傾斜計を用いた腰仙椎角の評価はMRIを用いた仙骨傾斜角と比べて計測値が過小評価されやすい可能性がある.しかしながら比例および偶然誤差は小さく,傾斜計で得られる数値を基に仙骨傾斜角の予測が可能となると考える.(著者抄録)

バスケットボールにおける足関節捻挫要因である,ポジション(ガード,フォワード,センター),受傷場面(試合,練習),受傷機転(接触の有無及び接触部位(足・足関節部,足・足関節部以外))の3点を複合的に検討し,足関節捻挫発生率との関連性を明らかにするために,大学女子バスケットボール選手延べ60名を対象に3シーズン33ヵ月の疫学調査を行った.単一因子での検討では,Forward,試合時,足部同士の接触による発生率がそれぞれ最も高かった.複数因子での検討では,Guardで試合時の足部同士の接触による発生率が最も高かった.単一因子と複数因子の検討間で結果に差異があることから,単一因子ではなく,複数因子によるより詳細な検討の必要性が明らかとなった.(著者抄録)

Abstract

Background

A flat foot is a common cause of chronic sports injuries and therefore many opportunities for arch support interventions exist. However, young athletes change their foot morphology due to developmental influences even without intervention. Therefore, developmental influences need to be considered when examining the effects of arch support, but there have not been sufficient longitudinal studies to date. This study aimed to determine the effect of the arch support intervention by performing a 9-weeks arch support intervention on the foot morphology and cross-sectional area of the foot muscles in flat-footed young athletes. Thirty-one elementary school boys (Age 11.4 ± 0.5 years, Height 145.2 ± 7.4 cm, Weight 38.8 ± 8.3 kg, BMI 18.2 ± 2.2 kg/m²) with a decreased medial longitudinal arch in the foot posture index were selected as participants from a local soccer club and randomly divided into two groups.

Methods

In one group, in the intervention period, an existing arch supporter was used to provide arch support, while in the other group, no special intervention was provided in the observation period. To account for developmental effects, the intervention study was conducted as an 18-weeks crossover study in which the intervention and observational phases were switched at 9 weeks after the intervention. Foot morphology was assessed using a three-dimensional foot measuring machine, and the cross-sectional area (CSA) of the internal and external muscles of the foot was assessed using an ultrasound imaging device. We examined the effect of the intervention by comparing the amount of change in the measurement results between the intervention and observation periods using corresponding t-tests and Wilcoxon signed-rank sum test, analysis of covariance methods.

Results

After adapting the exclusion criteria, 14 patients (28 feet) were included in the final analysis. The CSA of the abductor hallucis muscle (ABH) increased 9.7% during the intervention period and 3.0% during the observation period (p = 0.01). The CSA of the flexor digitorum longus muscle (FDL) increased 7.7% during the intervention period and 4.2% during the observation period (p = 0.02).

Conclusion

A 9-weeks arch supporter intervention may promote the development of the ABH and FDL CSA in young flat-footed soccer players.

<jats:p>The timing and tempo of growth rate varies inter-individually during adolescence and can have an impact on athletic performance. This study aimed to determine the difference in growth rate for each maturity status. We combined data collected both retrospectively and prospectively from 78 adolescent boys aged 12 years old; growth charts were collected from their elementary school records, and the height of each participant was subsequently measured every six months over a period of two years. Take Off Age (TOA), Peak Height Velocity Age (PHVA), and Final Height Age (FHA) were estimated using the AUXAL 3.1 program. Growth Tempo 1 and 2 were calculated by dividing the height increase by the time difference between TOA and PHVA, and FHA, respectively. Our results showed three group differences based on the maturation status of PHVA: Growth Tempo 1 and 2 were both higher in the early than during middle and late maturation. Additionally, entering the height at each event as a covariate, the group differences for Growth Tempo 1 did not change; however, for Growth Tempo 2, group differences were eliminated. Therefore, we conclude that during early maturation, growth from TOA to PHVA occurs rapidly and in a shorter period.</jats:p>

【目的】健常成人正常足と比較した回内足の足内在筋および外在筋の筋横断面積(以下、CSA)の違いを明らかにすることである。【方法】対象は健常成人25名50足(男性15名女性10名、年齢24.3±1.4歳、身長167.5±7.7cm、体重62.4±12.6kg、BMI22.1±3.0kg/m2)とした。CSAに関しては超音波画像診断装置を用いて、短母趾屈筋、母趾外転筋、短趾屈筋、長趾屈筋(以下、FDL)、長母趾屈筋(以下、FHL)、腓骨筋、後脛骨筋の測定を行った。その後Foot posture indexを用いて足部形態の評価を行い、回内足群、正常足群に群分けし、群間での各筋CSAの比較を行った。【結果】回内足群16足(男5名8足、女6名8足)では、正常足群32足(男11名20足、女8名12足)と比較しFDL(p=0.007)、FHL(p=0.04)のCSAが有意に大きかった。【結論】回内足群は正常足群と比較してFDL、FHLのCSAが有意に大きく、能動的足部支持機能としてはFDL、FHLが優位に機能することが示唆された。回内足に対して足部筋のトレーニングなどを行う際には、足部形態の特徴に留意する必要がある。(著者抄録)

【目的】中学生野球選手における投球障害肩の既往が上肢分節重量および肩甲帯除脂肪量に与える影響を明らかにすることを目的とした。【方法】対象は中学1〜3年生の野球選手149名とし、その内16名をInjured Shoulder群、133名をNon Injured群に分類し、比較検討を行った。測定はDXA装置を用い、whole body modeを用いて全身スキャンを行った。そしてSubRegion機能を用いて上肢を分画し、上腕、前腕、手部の重量、ならびに肩甲帯部の除脂肪量を算出した。上肢、上腕、前腕、手部の重量、肩甲帯除脂肪量、肩甲帯除脂肪量に対する上腕重量の群間比較にはt検定もしくはMann-WhitneyのU検定を用いた。また、上腕重量、上肢重量、肩甲帯除脂肪量については群間の体格差を考慮するため、体重を共変量とする共分散分析を実施した。【結果】前腕重量、上腕重量、上肢重量はInjured Shoulder群がNon Injured群と比較して有意に高値を示した(p=0.045、0.014、0.028)。また、肩甲帯除脂肪量に対する上腕重量はInjured Shoulder群がNon Injured群よりも有意に高値を示した(p=0.045)。共分散分析の結果、肩甲帯除脂肪量はInjured Shoulder群がNon Injured群と比較して有意に低値(p=0.028)を示した一方、上肢および上腕重量は高値を示した(p=0.049、0.046)。【結論】投球障害の既往を有する中学野球選手は上肢重量に対して肩甲帯筋量が不足することが明らかとなった。肩痛の既往は肩障害再発の危険因子となることから、肩甲帯除脂肪量の発育がピークとなる中学生期に肩甲骨周囲筋のトレーニングを介入することは再発予防に貢献する可能性がある。(著者抄録)

膝関節は下肢の中心に位置し人々のADLに重要な役割を担っている。その膝関節の正常な働きを可能にするのが動作の潤滑さと負荷の緩衝に寄与する軟骨である。軟骨厚は近年日本で増加する変形性膝関節症の発症と進行を説明する1つの重要な尺度であり、一般的に厚い軟骨は薄い軟骨よりも衝撃緩衡能力に優れ健康な軟骨と考えられている。運動と軟骨厚の関係を明らかにし後年においても正常な軟骨を保つ生活習慣を促すことは急務である。本研究では、超音波画像診断装置を用いて大学生の膝関節軟骨厚を測定し運動習慣や運動様式による違いを明らかにすることを目的とした。対象は大学生510名(男子356名、女子154名)、計1020膝とした。超音波画像診断装置を用いて大腿骨内側顆荷重部の軟骨厚を測定し、異なる運動習慣と運動様式を持つ群間で比較した。男子においては、バスケットボールや陸上競技など、下肢に高頻度、高強度の負荷がかかる競技において軟骨厚が厚かった。また、男子、女子ともに継続的な運動を行っていない非運動群ならびに荷重負荷のかからない競技である競泳は、他の群に比べ軟骨厚が薄い傾向が見られた。本研究結果から、運動習慣や下肢への荷重負荷が加わる運動の実施が軟骨厚を厚くしている可能性が示唆された。したがって、若年期の運動により正常な軟骨厚を保つことが、後年においても関節の働きを維持することに役立つ可能性が考えられる。(著者抄録)

We aimed to investigate the changes caused by focused extracorporeal shock wave pain therapy (f-ESWT) in patients with patellar tendinopathy by means of ultrasound imaging. We included 18 knees from 11 college athletes with patellar tendinopathy. We assessed the tendon thickness and blood flow of the patellar tendon using ultrasound imaging, rest pain using NRS and tenderness using a pressure pain gauge. We recorded four measurements: immediately before f-ESWT (PRE 1) and after f-ESWT (POST 1) and two weeks after the first irradiation before f-ESWT (PRE 2) and after f-ESWT (POST 2). Only the resting pain in both the first and second irradiations showed a significant difference immediately before and after the treatment. In terms of pain changes after two weeks later, we observed significant differences in the resting pain between PRE 1 and PRE 2 and also in the resting pain, tenderness and blood flow area between PRE 1 and POST 2. No significant difference was seen in the tendon thickness. We concluded that pain in the patellar tendon at rest decreased before and after irradiation, suggesting that f-ESWT may have influenced the nociceptive structures and had an analgesic effect.

BACKGROUND: Identifying the characteristics of physical function and muscle strength related to swing velocity is necessary for improving batting performance. The purpose of this study was to identify the factors related to swing velocity in youth baseball players. METHODS: 191 youth baseball players aged 7-13 years old participated and were divided into the Tee Ball (˂9.5 years) and Major (≥9.5 years) divisions. We measured the swing velocity for batting performance, medicine ball (MB) back throw and modified star excursion balance test (SEBT) for physical function, and hip muscle torque for lower extremity muscle strength. RESULTS: Height and MB back throw (β=0.403 and 0.380) for physical function (R2=0.646), and height and internal rotation (IR) torque of the step leg (β=0.620 and 0.216) in lower extremity muscle strength (R2=0.616) were all extracted as related independents for the multiple regression analysis on swing velocity in all subjects. Additionally, height, MB back throw and modified SEBT in the pivot leg (β=0.420, 0.324 and 0.218) for the Major division (R2=0.579), and IR torque of the pivot leg and step leg (β=0.555 and 0.525) for the Tee Ball Division (R2=0.568) were selected. CONCLUSIONS: Swing velocity was related to height, MB back throws on physical function, and IR torque of the stepping leg in lower extremity muscle strength in youth baseball players. Therefore, the explosive power and strength for stopping the body opposite to the hitting direction are considered necessary to increase the swing velocity.

BACKGROUND: In understanding the onset factors associated with Plantar heel pain and the structure of heel fat pad, measuring its thickness is the most basic frequently reported evaluation. This study aimed to determine changes to heel fat pad thickness associated with age and gender and the relationship between heel fat pad thickness, age, and physique in Japanese. METHODS: This study was carried out in 1126 healthy individuals between the ages of 1 and 96 years. Participants were categorized according to age. Heel fat pad thickness was measured with an ultrasonography device using a linear ultrasonography probe. FINDINGS: Heel fat pad tends to become thicker from ages 1-5 to 30-44 years and thinner from ages 30-44 to 80-96 years. Heel fat pad thickness in males and females was similar within each group, and males had higher heel fat pad thickness than females of corresponding ages. Heel fat pad thickness of males had a good correlation with height and body mass. Moreover, male heel fat pad thickness had a fair correlation with age. Heel fat pad thickness of females had a moderate correlation with height and body mass and a fair correlation with age. INTERPRETATION: Heel fat pad thickness became thicker from ages 1-5 to 30-44 years and thinner from ages 30-44 to 80-96 years. Females had a lower heel fat pad thickness than males of corresponding ages. This result suggests that higher heel fat pad thickness in males is related to body mass and height.

It is important to understand the timing of the maximum increase of forearm-hand inertia value and lean body mass (LBM) of the shoulder girdle musculature when elbow injury frequently occurs. This study aimed to clarify the discrepancies of those in youth baseball players. Forty-three male baseball players (8- to 14-years-old) participated in this study. The forearm-hand inertia value and LBM of the shoulder girdle musculature were calculated using dual-energy X-ray absorptiometry (DXA). A cubic spline fit was applied to the annual increase forearm-hand inertia value and LBM of the shoulder girdle musculature for each chronological age and years from peak height velocity (PHV) age. As a result of cubic splines fitting, the peak timing for forearm-hand inertia value and LBM of the shoulder girdle musculature was 12.42 and 12.75 years in chronological age, -0.66 and -0.11 years in PHV age. Therefore, the peak timing of forearm-hand inertia value was about 4 months earlier in chronological age and half a year earlier in PHV age than LBM of the shoulder girdle musculature. Acquiring sufficient shoulder girdle musculature during the period when the growth of the shoulder girdle musculature cannot catch up with forearm-hand inertial value is necessary to reduce the elbow load while throwing.

The purpose of this study was to identify the growth changes of the inertial in baseball players from both chronological age and relative growth, and to play a part in the elbow injury prevention. The subjects were 184 baseball players from elementary school students to university students. A whole body scan was performed using a DXA device, and the forearm-and-hand inertia were calculated according to Ganley’s method of calculating the inertia. In addition, the inertia ratio was calculated by the forearm-and-hand inertia for the region of scapular lean mass and the inertia ratio of that under the condition of the ball holding. In addition, the allometry method was used to determine the inertia ratio and the inertia ratio of ball holding condition from the viewpoint of relative growth based on height. The inertial ratio showed the peak at the age of 12 or about 150 cm in height, suggesting an increased risk of elbow disorders at this time.

本研究は発育過程にある野球選手の前腕・手部慣性値の変化、ならびに肩甲帯部除脂肪量に対する前腕・手部慣性値の変化を明らかにすることで、肘障害リスクの考察の一助とすることを目的とした。対象は小学生から高校生までの野球選手120名とし、DXA装置を用いて全身スキャンを行った。そしてSub-Region機能を用い、最小にした関心領域を投球側の肘関節から手指末梢まで並べ、それぞれの質量データを抽出した。その後n番目までの質量×関節からの距離の二乗の積分値をもって前腕・手部慣性値とした。また、上肢を支持する肩甲帯部除脂肪量を算出し、肩甲帯除脂肪量に対する前腕・手部慣性値で求められる慣性値比を算出した。前腕・手部慣性値は線形に近い形で回帰したが、暦年齢において11歳頃、PHV経過年数において約2年前を境に傾きが増加傾向にあった。慣性値比は暦年齢で12歳頃、PHV経過年数で約-2年まで増加し、その後はやや減少傾向にあるもののほぼ横ばいであった。暦年齢で12歳頃、また身長最大増加時期を迎える約2年前までは上肢を支持する肩甲帯部除脂肪量が相対的に不足しており、肘への負荷が高まり障害発生の一要因となりうる。(著者抄録)

【緒言】健常投手、肩痛投手および一般人を対象とし肩甲骨面上での外転角度の違いによる肩関節位置覚を硬式球保持・非保持で比較することで、肩障害ならびに投手の競技特性が肩関節位置覚に与える影響を明らかにすることを目的とした。【方法】対象は健常投手9名、肩痛投手6名、一般人9名とした。肩関節位置覚測定はBalkeらの方法を改良し、上腕近位部にレーザーポインターを装着して行った。座位姿勢にて、肩関節水平内転30°上での外転60、90、および120°の関節位置覚測定を硬式球保持・非保持の2条件で行った。【結果】硬式球保持時では、外転60および90°におけるcontrol群と野球健常群との間、外転120°における野球健常群と野球肩痛群との間に有意な差が見られた(p=0.017および0.040、0.002)。さらに野球健常群は外転60と120°、90と120°との間に有意な差が認められた(ともにp=0.005)。【考察】固有感覚には学習の要素があり、利き手の方が高値を示すとされている。このことから肩関節外転位で投球動作を繰り返し行う投手の競技特性の影響が考えられる。また、随意運動であるリリース動作の繰り返しが健常投手の肩関節位置覚の高値につながったと推察できる。【結論】健常投手において、硬式球保持時の肩甲骨面上における外転120°での関節位置覚は高値を示し、競技特性を反映する可能性が示唆された。(著者抄録)