論文

© 2015 Elsevier B.V. The purpose of this study was to quantify activation of the biceps femoris (BF) and medial hamstring (MH) during overground sprinting. Lower-extremity kinematics and electromyography (EMG) of the BF and MH were recorded in 13 male sprinters performing overground sprinting at maximum effort. Mean EMG activity was calculated in the early stance, late stance, mid-swing, and late-swing phases. Activation of the BF was significantly greater during the early stance phase than the late stance phase (p< 0.01). Activation of the BF muscle was significantly lower during the first half of the mid-swing phase than the other phases (p< 0.05). The MH had significantly greater EMG activation relative to its recorded maximum values compared to that for the BF during the late stance (p< 0.05) and mid-swing (p< 0.01) phases. These results indicate that the BF shows high activation before and after foot contact, while the MH shows high activation during the late stance and mid-swing phases. We concluded that the activation properties of the BF and MH muscles differ within the sprinting gait cycle.

© 2016 EDIZIONI MINERVA MEDICA. BACKGROUND: hamstring strain injuries often occur during sprinting. Many factors have been hypothesized to cause these injuries. the purpose of this study was to investigate the effects of the strength ratios in the hip and knee joints, contralateral hip flexor tightness, and hamstring flexibility on musculotendon length of the biceps femoris long head during sprinting for providing a better understanding of this multifactorial injury. METHODS: Twelve male sprinters performed maximal effort overground sprinting. A three-dimensional musculoskeletal model was used to compute musculotendon length of the biceps femoris in a sprinting gait cycle. the straight leg raising (SLR) test, Thomas test of the contralateral limb, and hamstrings-to-quadriceps and hip extensors-to-flexors strength ratios were measured. Stepwise linear regression analysis was used to assess whether factors measured could predict the biceps femoris length during terminal swing of sprinting. RESULTS: Decreased hip extensors-to-flexors ratio and SLR scores and increased contralateral Thomas test scores predicted 53.2% of variance in biceps femoris muscle length, at peak knee extension during terminal swing (P<0.05). CONCLUSIONS: The results indicate that a composite factor including a combination of hamstring flexibility, contralateral hip flexor tightness, and hip extensors-to-flexors strength ratio can predict biceps femoris musculotendon length during the terminal swing phase of sprinting.

© 2017 Informa UK Limited, trading as Taylor & Francis Group. This study aimed to investigate activation characteristics of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles during the acceleration and maximum-speed phases of sprinting. Lower-extremity kinematics and electromyographic (EMG) activities of the BFlh and ST muscles were examined during the acceleration sprint and maximum-speed sprint in 13 male sprinters during an overground sprinting. Differences in hamstring activation during each divided phases and in the hip and knee joint angles and torques at each time point of the sprinting gait cycle were determined between two sprints. During the early stance of the acceleration sprint, the hip extension torque was significantly greater than during the maximum-speed sprint, and the relative EMG activation of the BFlh muscle was significantly higher than that of the ST muscle. During the late stance and terminal mid-swing of maximum-speed sprint, the knee was more extended and a higher knee flexion moment was observed compared to the acceleration sprint, and the ST muscle showed higher activation than that of the BFlh. These results indicate that the functional demands of the medial and lateral hamstring muscles differ between two different sprint performances.

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. In this study, we aimed to clarify the characteristics of neuromuscular function, kinetics, and kinematics of the lower extremity during sprinting in track and field athletes with a history of strain injury. Ten male college sprinters with a history of unilateral hamstring injury performed maximum effort sprint on an athletic track. The electromyographic (EMG) activity of the long head of the biceps femoris (BFlh) and gluteus maximus (Gmax) muscles and three-dimensional kinematic data were recorded. Bilateral comparisons were performed for the EMG activities, pelvic anterior tilt angle, hip and knee joint angles and torques, and the musculotendon length of BFlh. The activity of BFlh in the previously injured limb was significantly lower than that in the uninjured limb during the late-swing phase of sprinting (p < 0.05). However, the EMG activity of Gmax was not significantly different between the previously injured and uninjured limbs. Furthermore, during the late-swing phase, a significantly more flexed knee angle (p < 0.05) and a decrease in BFlh muscle length (p < 0.05) were noted in the injured limb. It was concluded that previously injured hamstring muscles demonstrate functional deficits during the late swing phase of sprinting in comparison with the uninjured contralateral muscles.

© 2020 Higashihara et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 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.

Hamstring strain often occurs when an opponent unanticipatedly perturbs an athlete’s movements. We examined the neuromuscular responses of hamstring and trunk muscles during unanticipated trunk perturbations in athletes with and without a history of hamstring strain injury. Male college athletes (11 with a history of a unilateral hamstring injury and 10 without prior injury) knelt while wearing a chest harness attached to a cable that was pulled backward. They were instructed to resist the force isometrically and maintain their position when the perturbations were applied. The pressure was released with or without a cue (CUE or NoCUE). We measured trunk acceleration, three-dimensional kinematic data, and surface electromyography (EMG) signals of the erector spinae, internal oblique, gluteus maximus, biceps femoris long head, and semitendinosus muscles. Maximum trunk acceleration and displacement were greater with NoCUE in both groups (p < 0.05). EMG amplitude did not differ after perturbation of any investigated muscle. The injured group demonstrated a delayed onset of the gluteus maximus and erector spinae muscles in NoCUE versus CUE stimuli (p < 0.05). Athletes with a history of hamstring strain injury exhibited a reduced neuromuscular coordination of the lumbopelvic muscles in response to unanticipated trunk movement.

The semitendinosus (ST) muscle is primarily used during Nordic hamstring exercise (NHE), which is often prescribed for preventing hamstring injury, though the biceps femoris long head (BFlh) muscle that is more susceptible to injuries. Thus, this study aimed to identify the modulation of BFlh muscle activity with different knee flexion angles during NHE using an inclined platform. Fourteen male athletes performed NHE and maintained their position at maximum inclination (NH). Subjects also performed isometric NHE using a platform inclined to 50° (ICL) and 40° (ICH), and the knee flexion angle was controlled to 50° and 30°. The electromyography (EMG) activity of the BFlh, ST, semimembranosus, gluteus maximus, elector spinae, and rectus abdominus muscles was determined during each exercise. The EMG of the ST was higher than that of the BFlh during NHE and the highest of all muscles in all exercises (p < 0.05). Moreover, the activity of the BFlh tended to be higher than that of the ST for ICH than for ICL, regardless of the knee joint angle. The activity of the BFlh becomes equivalent to that of the ST during NHE at a knee flexion angle of less than 50°. These results indicate that performing NHE at a shallow knee flexion angle will enhance the activity of the BFlh muscle.

The neuromuscular activity in the hamstring and quadriceps muscles is vital for rapid force control during athletic movements. This study aimed to investigate the recruitment properties of the corticospinal pathway of the biceps femoris long head (BFlh) and rectus femoris (RF) muscles. Thirty-two male subjects were participated in this study. Corticospinal excitability was investigated for BFlh and RF during the isometric knee flexion and extension tasks, respectively, using transcranial magnetic stimulation. A sigmoidal relationship was observed between the stimulus intensity and amplitude of motor-evoked potentials and characterized by a plateau value, maximum slope, and threshold. Compared with RF, BFlh had a significantly lower plateau value (P < 0.001, d = 1.17), maximum slope (P < 0.001, r = 0.79), and threshold (P = 0.003, d = 0.62). The results showed that the recruitment properties of the corticospinal pathway significantly differ between BFlh and RF. These results reveal that when a sudden large force is required during athletic movements, the RF can produce force through a rapid increase in the recruitment of motor units. The BFlh, on the other hand, requires larger or more synchronized motor commands for enabling the proper motor unit behavior to exert large forces. These differences in the neurophysiological factors between the hamstrings and quadriceps can have a substantial effect on the balance of force generation during athletic activities.

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

研究資料

【諸言】コロナ禍の外出自粛や遠隔授業の実施による身体活動制限下において大学生の心身の健康に関わる諸問題が懸念されている。そうした中、大学の体育実技について、2020年度春学期は対面形式での実施を見送った大学が多かったが、秋学期には一部の大学で対面形式による実施が再開された。本研究では、春学期の休講措置の後、秋学期に対面形式で実施された体育実技が大学1年生の身体不活動時間とライフスキルに与える影響・効果について検討することを目的として調査を実施した。【方法】対象は首都圏の私立大学に在籍している1年生277名とした（男性136名、女性141名）。体育実技履修者は201名、非履修者は76名であった。調査はWebアンケートにより2020年度秋学期授業期間（10月-12月）の前後で計2回実施した。調査内容は（1）身体不活動時間（2）ライフスキル尺度（目標設定・考える力・謙虚な心・感謝する心）について質問項目を設定した。【結果】2要因の分散分析（時間要因×履修要因 ）の結果、身体不活動時間について履修者と非履修者ともに授業期間前後で減少傾向にあり、有意な交互作用は認められなかった。ライフスキル尺度の「目標設定」と「感謝する心」においては交互作用効果が認められた。さらに、運動部に所属していない学生に限定した比較では、身体不活動時間については有意な交互作用が認められなかったが、ライフスキル尺度の４因子すべてにおいて交互作用効果が認められた。【まとめ】本研究の結果は、対面形式で再開した体育実技履修が秋学期中の身体活動量の増加を有意に促進したものではないが、体育実技が大学１年生のライフスキルの獲得に貢献することを示した。特に、運動部に所属していない大学１年生にとって体育実技履修の効果が顕著に見られたことは、対面による体育実技実施の教育的意義を高めると考えられる。

慶應義塾大学 (日吉キャンパス) は横浜市、川崎市とともに東京2020オリンピック・パラリンピックに出場する英国代表チームを受け入れる。本編では、その際に躍動する学生ボランティアを養成するための教育プログラム【KEIOスポーツレガシー】を実践する組織「KEIO 2020 project」の活動を紹介する。特集 オリパラ サイコウ招待論文 : 実践報告

type:text

大学体育実技授業は，対面授業による実施を前提に心身の健康の維持・改善に寄与してきた．しかし，新型コロナウイルス感染症パンデミックの影響により，2020年度春学期（前期）に多くの大学で対面授業による体育実技が実施不可となり，その授業形態を遠隔授業に変更し，大学によっては休講を決定した．このような極めて特殊な状況下において，特に大学生のメンタルヘルスや社会的スキルへの否定的な影響が懸念されていた中，筆者らの所属する大学（以下本学）では，2020年度秋学期（後期）に体育実技を対面授業で再開するのに際し，これらの要素に対する体育実技の肯定的な教育的効果が期待された．そこで，本研究では，対面授業による体育実技の履修が大学生のメンタルヘルスの向上および社会的スキルの育成に与える影響を検証することを目的とした．対象者は本学の学生455名（男性230名，女性225名）であった．体育実技授業を履修した者は316名（履修者群），履修していなかった者は139名（非履修者群）であった．調査は2020年度秋学期授業期間の前後でWeb アンケートによって実施した．Web アンケートは対象者の属性，精神的健康状態表（WHO-5），社会的スキル尺度（KiSS-18）から構成した．結果は以下の通りである．（1）二要因分散分析の結果，WHO-5とKiSS-18において履修要因と時間要因で有意な交互作用が認められた．また，WHO-5は履修者群で向上，KiSS-18では非履修者群で低下の傾向が示された．（2）課外活動への所属有無を踏まえた検討では，KiSS-18の得点について有意な交互作用が認められた．特に，課外活動に所属している非履修者群において，受講後の得点が受講前のKiSS-18の得点に比べて有意に低かった．（3）履修種目を踏まえた検討では，WHO-5とKiSS-18において有意な交互作用が認められなかった．結論として，体育実技の履修が授業期間前後においてメンタルヘルスの向上，および社会的スキルの維持に寄与したことが示された．とりわけ，その維持・促進要因として課外活動への所属有無や履修種目の違いは関連が小さく，体育実技への参加が最も影響を与えている要因のひとつである可能性が示された．

本研究は，大学体育実技の成績評価の観点と方法に関してアンケート調査を実施し，従来の方針と新型コロナウイルス感染症拡大下（以下，「コロナ禍」と略す）における対応について，その実態を分析することを目的とした．調査内容は，教養体育科目の開講状況，2020年度秋学期と2021年度春学期の授業実施形態と実施理由，成績評価方法に関する従来の方針と遠隔授業による対応，などであった．有効回答が得られた131校（19.2％）を分析の対象とした．回答結果の分析から，成績評価の観点は技術や技能，知識や理解，態度や意欲，出席の4つに分類でき，それぞれに対応する評価方法として，実技テスト，レポートや筆記テスト，教員の観察，出席回数が代表的なものとして示された．しかし，「配分や方法は担当教員に一任」という回答も多く，厳格な成績評価を行う「アセスメント・ポリシー」の取り組みとしては課題と考えられた．コロナ禍に対面のみで体育実技を実施できたのは2020年度秋学期で51校（38.9％），2021年度春学期で61校（46.6％）であり，半数以上は遠隔を含む展開がなされていた．成績評価方法に関してコロナ禍に新たな対応を行ったのは54校であった．その内容は，「評価の観点・配分・方法等を再構築」，「従来の観点を評価するための補足的方法を付加」，「従来よりも課題・レポートの比率が増加」などであった．本研究は，近年における大学体育実技の成績評価方法の実態を明らかにし，また遠隔授業の導入による成績評価方法の新たな対応について情報を得た点で，大学教育改革を進める上での資料的価値が高いと考えられる．

type:text