Published papers

© 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.

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 (T-2)-weighted magnetic resonance images (MRI). 20 healthy collegiate marathon runners (15 males) were recruited for this study. T-2-MRI was performed before (PRE) and at 1 (D1), 3 (D3), and 8 days (D8) after marathon, and the T(2)values of each hamstring muscle at the distal, middle, and proximal sites were calculated. Results indicated that no significant intermuscular differences in T(2)changes were observed and that, regardless of muscle, the T(2)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. T(2)significantly increased at distal and middle sites of the biceps femoris long head on D1 (p= 0.030 andp= 0.004, respectively) and D3 (p= 0.007 andp= 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 andp= 0.040, respectively) and D3 (p= 0.002 andp= 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.

The purpose of this study was to examine the current health status and physical activity levels among students at Keio University under public restrictions during the COVID-19 pandemic. The findings are outlined as follows.1) About 47% of the students in this study had not achieved the recommended amount of physical activity for the prevention of lifestyle-related diseases. In addition, about 35 % of the students were likely to be in a depressive state.2) The group of students who had not achieved the standard amount of physical activity reported lower mental health levels and life skill scores for physical health management than those who had reached the standard amount of physical activity.3) The findings indicated the importance of practical physical education that can promote physical and mental health. Furthermore, it is necessary to provide students with guidance on health management, information that aims at promoting physical activity, and opportunities to be physically active.

【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

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There is a broad understanding that the primary benefit of in-person-teaching of university physical education classes develops students’ physical and mental health. However, to adapt to restricted mobility due to the COVID-19 pandemic, most universities had to cancel in-person classes in the spring term (first semester) 2020. While some universities decided to cancel physical education classes, others shifted online. There are concerns about the adverse effects on students’ mental health and social skills during this unusual situation. Subsequently, our university returned to in-person teaching of physical education classes from the autumn term (second semester) 2020. Within this context, in-person teaching is promising for the expected educational benefits of university physical education. Therefore, this study aimed to examine the effects of in-person physical education classes on students’ mental health and social skills. The study recruited 455 students (230 males and 225 females) in our university. A total of 316 students attended in-person physical education classes (PE group), and 139 students did not register for the classes (non-PE group). We administered web-based questionnaires to the participants pre- and post-the 2020 autumn term. The questionnaires consisted of a survey of physical activity opportunities, the WHO-5 Well-Being Index (WHO-5), and the Kikuchi’s Scale of Social Skills (KiSS-18). The results revealed the following: (1) The two-way mixed ANOVA results showed that the Time x Group interaction effect was significant for the WHO-5 and KiSS-18. Specifically, the PE group students improved in the WHO-5 score, while students in the non-PE group declined in the KiSS-18 score; (2) Concerning the status of belonging to university athletics club or sports club, the Time x Group interaction effect was significant for the KiSS-18. Expressly, the non-PE group who belong to university athletics club or sports club significantly declined in the KiSS-18 score; (3) The analysis including the type of sport showed no significant Time x Group interaction effect for the WHO-5 and KiSS-18. We concluded that attending in-person physical education classes had a significant positive effect on enhancing their psychological wellbeing and social skills. Notably, attending physical education classes, rather than the type of sport and belonging to a university athletics club or sports club, was one of the most influential factors in promoting and maintaining mental health and social skills.

This study aimed to examine the status of the conventional policy on the perspectives and practices of assessment in physical education at Japanese universities, and to analyze their responses to the shift to remote classes during the COVID-19 pandemic. An online survey was administered, which included the following items: the status of physical education classes for liberal arts; the forms of teaching and the reasons for offering them in the fall semester of 2020 and the spring semester of 2021; and the existing policy regarding assessment methods and the response to the shift to remote classes. Valid responses provided by 131 universities (19.2%) were included in the analysis. The assessment criteria could be classified into four categories: techniques and skills, knowledge and understanding, attitude and motivation, and attendance. The most common assessment methods corresponding to each were practical skill tests, reports and written tests, teacher observation, and attendance counts. However, many respondents stated that the distribution and methods were left up to individual faculty members in charge, which was considered a challenge for the Assessment Policy initiative for authentic assessment. The number of universities that conducted only in-person physical education classes during the pandemic was 51 (38.9%) in the fall semester and 61 (46.6%) in the spring semester, and more than half of them shifted to remote classes. New measures regarding assessment methods were taken in 54 universities to adapt to the situation during the pandemic. These included ‘restructuring the assessment criteria’, ‘distribution, and methods; providing supplemental methods using conventional criteria’; and ‘increasing the ratio of assignments and reports’ compared to the past. This study sheds light on the actual assessment practices in university physical education and provides information on new measures for assessment methods due to the adoption of remote classes, which can lead to promoting higher education reform.

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