This study aimed to compare the foot muscle morphology and foot posture between healthy adults and lifesavers in sandy beach sports. The participants included 15 lifesaver athletes and 15 healthy adults. Using a non-contact three-dimensional foot measurement device, the foot length, width, and arch height of the right foot were measured while standing and sitting without back support, and the transverse arch length ratio and arch height index were subsequently calculated. Muscle cross-sectional area was measured using an ultrasound imaging device. Muscle cross-sectional areas, arch height, foot width, arch height index, and transverse arch length ratio were larger in the lifesaver than in the healthy adult group. Lifesavers had higher arches and more developed intrinsic and extrinsic muscles than healthy adults. Performing physical activity while barefoot on sandy beaches may effectively develop the foot intrinsic and extrinsic muscles and raise the arch.

Long-distance running results in lowering of the foot medial longitudinal arch, but it is unknown whether the left and right arches decrease equally. This study aimed to determine whether foot arch asymmetry increases upon completion of a full marathon and to identify factors capable of explaining the degree of asymmetry of navicular height and navicular height displacement. The three-dimensional foot posture data of 74 collegiate runners were obtained using an optical foot scanner system before (PRE) and immediately after (POST) a full marathon. The navicular height and arch height ratio (normalised navicular height by foot length) of both feet significantly decreased from PRE to POST full marathon completion (44.3 ± 6.3 mm versus 40.8 ± 6.5 mm, 17.8 ± 2.5 versus 16.6 ± 2.7, respectively; p < 0.001, both). The asymmetry of the arch height ratio was significantly greater POST than PRE marathon. Multiple linear regression analysis indicated that the POST-race Asymmetry Index (AI) of navicular height was significantly predicted by the PRE-race AI of navicular height; navicular height displacement was predicted by PRE-race navicular height and the marathon time. Full marathon running induced increasing asymmetry and lowering of the medial longitudinal arch in runners.

PURPOSE: The flexor digitorum longus and posterior tibial tendon as well as the perforating veins are located along the distal posteromedial tibial border. Adipose tissue may surround these structures and possibly play a role in reducing mechanical stress. This study aimed to examine the adipose tissue along the posteromedial tibial border via magnetic resonance imaging (MRI), ultrasound, and gross anatomical examination. METHODS: The lower legs of 11 healthy individuals were examined every 3 cm from the medial malleolus using MRI and ultrasound. The fat fraction was calculated using fat fraction images. In addition, the gross anatomy of the flexor digitorum longus origin and adipose tissue along the posteromedial tibial border was examined in seven fresh cadavers. The fat fraction was compared at different heights along the posteromedial tibial border and in Kager's fat pads; we also compared the height of the flexor digitorum longus origin and adipose tissue. RESULTS: In vivo, the adipose tissue was identified along the entire posteromedial tibial border using MRI and ultrasound. There was no significant difference in fat fraction between Kager's fat pads and the adipose tissue along the posteromedial tibial border, except at the 6 cm mark. All seven cadavers presented adipose tissue along the posteromedial tibial border, significantly more distal than the flexor digitorum longus origin. CONCLUSION: The adipose tissue was identified along the posteromedial tibial border via MRI, ultrasound, and gross anatomical examination; thus, this tissue may play a role in reducing friction and compressive stress in tendons.

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.

The peak increase in lean mass in adolescents is delayed from peak height velocity (PHV), and muscle flexibility temporarily decreases as bones grow. If the decrease in muscle flexibility is caused by muscle elongation, the relationship between the exerted torque and the joint angle could change in adolescents. The purpose of this study was to investigate the change in the optimum angle of force production due to growth. Eighty-eight healthy boys were recruited for this study. Isokinetic knee extension muscle strength of the dominant leg was recorded. The outcome variable was the knee flexion angle when maximal knee extension torque was produced (optimum angle). The age at which PHV occurred was estimated from subjects' height history. We calculated the difference between the age at measurement and the expected age of PHV (growth age). A regression analysis was performed with the optimal angle of force exertion as the dependent variable and the growth age as the independent variable. Then, a polynomial formula with the lowest p-value was obtained. A significant cubic regression was obtained between optimum angle and growth age. The results suggest that the optimum angle of force production temporarily changes in male adolescence.

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.

本研究は野球選手の発育に伴う慣性値の変化を暦年齢ならびに相対発育の2つの発育指標から明らかにし，肘障害予防の一端を担うことを目的とした．対象は小学生から大学生までの野球選手133名とした．DXA装置を用いて全身スキャンをし，Ganleyの慣性モーメントの算出法に準じて，前腕・手部慣性値を算出した．また，肩甲帯部除脂肪量に対する前腕・手部慣性値を示す慣性値比，野球ボール保持想定での慣性値比を求めた．さらにアロメトリー法を用いて身長に基づく相対発育の観点から慣性値比および野球ボール保持想定での慣性値比の変位点を求めた．慣性値比は12歳頃，または身長約150cmでピークとなり，この時期には肘障害のリスクが高まることが示唆された．

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)

Previous studies suggest that marathon running induces lower extremity muscle damage. This study aimed to examine inter- and intramuscular differences in hamstring muscle damage after a marathon using transverse relaxation time (T2)-weighted magnetic resonance images (MRI). 20 healthy collegiate marathon runners (15 males) were recruited for this study. T2-MRI was performed before (PRE) and at 1 (D1), 3 (D3), and 8 days (D8) after marathon, and the T2 values of each hamstring muscle at the distal, middle, and proximal sites were calculated. Results indicated that no significant intermuscular differences in T2 changes were observed and that, regardless of muscle, the T2 values of the distal and middle sites increased significantly at D1 and D3 and recovered at D8, although those values of the proximal site remained constant. T2 significantly increased at distal and middle sites of the biceps femoris long head on D1 (p = 0.030 and p = 0.004, respectively) and D3 (p = 0.007 and p = 0.041, respectively), distal biceps femoris short head on D1 (p = 0.036), distal semitendinosus on D1 (p = 0.047) and D3 (p = 0.010), middle semitendinosus on D1 (p = 0.005), and distal and middle sites of the semimembranosus on D1 (p = 0.008 and p = 0.040, respectively) and D3 (p = 0.002 and p = 0.018, respectively). These results suggest that the distal and middle sites of the hamstring muscles are more susceptible to damage induced by running a full marathon. Conditioning that focuses on the distal and middle sites of the hamstring muscles may be more useful in improving recovery strategies after prolonged running.

＜文献概要＞はじめに 踵骨下に存在する脂肪組織は,踵部脂肪褥,heel fat padと呼ばれており,主な役割として,足底部への衝撃を吸収するshock absorberとしての機能があげられる.踵部着地の際に衝撃が加わることで,隔壁のあるコラーゲン袋の中で脂肪の粒が拡散し,それらの中隔が変形することで衝撃が吸収されると考えられている.サッカーは非対称性動作競技の一つであり,ボールを蹴る蹴り脚と,蹴る際に体重を支える軸脚にわけられる.脚の使用用途が異なることから,軸脚と蹴り脚それぞれに加わる負荷にも差異があることが予想される.また,踵部へ加わる衝撃への適応として,踵部脂肪褥構造(厚さ,硬度など)が変化することが報告されている.サッカー特有動作であるインステップキック動作時に,軸脚には通常歩行の6〜9倍の負荷が加わっているとされており,踵部に加わる負荷や頻度の差異から,サッカー選手の踵部脂肪褥構造に左右差が生じていることが考えられる.そこで本研究では,中学生サッカー選手における踵部脂肪褥厚と踵部脂肪褥硬度に着目し,蹴り脚と軸脚間での左右差を検討することを目的とした.

踵骨下に存在する踵部脂肪褥は、heel fat padとも呼ばれる脂肪組織で、構成要素の異なる浅層のmicrochamber layer(MIC)と深層のmacrochamberlayer(MAC)の大きく2層から構成されており、歩行などの際にクッション機能として働く。本研究では、超音波B-modeによる押し込み手法の前後の変化量とMICとMACの硬度値の相関を検討し、クッション機能を評価する手法について検討することを目的とした。押し込み変化量とMICのSRとの相関は見られなかったが、MACのSRと有意な正の相関が見られた。RTE法による踵部脂肪褥の硬度測定は、MACの弾性評価に有用である。(著者抄録)

画像解析技術の進歩にともなって、骨格筋3特性のひとつ、質的特性に関する研究が盛んに行われている。超音波エラストグラフィを用いた当該研究領域では、原理原則の異なるいくつかのエラストグラフィ手法が用いられているものの、従来の体表面から押圧した評価法や関節運動をともなった測定法とは一線を画し、画像から生体軟部組織硬度の位置情報を取得できる点に最大の特徴がある。筋の硬さを個別に評価できる利点は、特定の筋のみに焦点を絞った経時変化の観察が可能になることを示しており、特異的なリカバリー手法を提供する起点となっている。本編では、超音波エラストグラフィを用いて評価される筋の質的特性の概略と、硬化した筋に対する戦略的なリカバリー方策(経口補水液と特殊シューズ)の知見に関して報告する。(著者抄録)