Journal of High Performance Sport
Online ISSN : 2434-7302
Print ISSN : 2434-7299
Volume 6
Displaying 1-16 of 16 articles from this issue
  • Toshiharu Yokozawa, Mariko Nakamura
    2020 Volume 6 Pages 1-11
    Published: 2020
    Released on J-STAGE: April 26, 2020
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    Although the double sculling technique includes crew coordination, that indicates similar oar motion pattern between rowers, few studies have identified the difference in the oar motion between single and double sculling by the same rowers on water or investigated how to change and control the oar motion in double sculling. This study aimed to identify the control the oar motion and force between rowers during double sculling. In this study, we compared the difference in oar motion and oar force between single and double scull rowing on water using a rowing instrumentation system. Two Japanese female rowers rowed on single scull boats and a double scull boat for every 10 strokes at a pace corresponding to a 2,000 m race. The difference in each parameter at 10 strokes between single and double sculling was tested using a factorial analysis of variance. The recovery time was significantly increased and the stroke rate was significantly decreased in the bow rower during double sculling compared with those during single sculling. Additionally, the time from finish to catch during the recovery phase significantly correlated between the stroke rower and the bow rower in double sculling. The bow rower significantly decreased the oar angular displacement during the driving phase in double sculling to be closer to the value of the stroke rower. On the other hand, the oar force of the bow rower during the first half of the driving phase in double sculling was much smaller than that in single sculling, increasing the bilateral difference and the difference among strokes. It appeared to be reasonable that the bow rower controlled the oar motion adjusting to the stroke rower because the bow rower could watch the motion of the stroke rower.
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  • a questionnaire-based study of the 2016 Japanese Wrestling Championship
    Mio Nishimaki, Emi Kondo, Cheryl Teo, Kohei Nakajima, Daichi Yamashita
    2020 Volume 6 Pages 12-27
    Published: 2020
    Released on J-STAGE: April 26, 2020
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    This study aims to investigate weight loss practices of elite Japanese wrestlers who participated at the 2016 Japanese Wrestling Championship. In this study, we defined rapid weight loss (RWL) as losing 5% or more of their weight relative to their intended weight class, one week before weigh-in. 241 wrestlers completed a questionnaire on their weight loss practices. 109 wrestlers reported RWL and were used for analysis. We found that wrestlers who cut weight over a longer duration utilized a greater variety of weight loss methods than those who cut weight over a shorter duration. Reduced carbohydrate intake was commonly used by wrestlers who cut weight over a longer duration utilized a greater variety of weight loss methods than those who cut weight over a shorter duration. Dehydration was commonly done by all wrestlers. We also identified that the use of low carbohydrate and low salt diets are not optimized for RWL, and suggest for wrestlers to be educated to improve the effectiveness of these methods. Studies to investigate the revision of the weigh-in rules are recommended to better understand the implications of these changes on RWL and recovery practices in wrestlers.
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  • Daichi Yamashita, Mio Nishimaki, Hideyuki Nagao, Michio Ikeda, Mikio N ...
    2020 Volume 6 Pages 33-43
    Published: 2020
    Released on J-STAGE: August 28, 2020
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    Wrestlers are categorized into a series of weight classes to ensure fair competition. Since the implementation of new rules in January 2018, weight categories and the timings of weigh-ins have changed. The purpose of the study was to establish baseline physical profiles, such as body composition, muscle strength, power, and endurance for Japanese elite freestyle wrestlers in each of the new weight classes. We collected a total of 242 data points from 70 elite Japanese male freestyle wrestlers at 14 training camps over two years. Body composition measurements, one-repetition maximum tests (bench press, parallel back squat, one-handed dumbbell snatch, and weighted chinup) and muscle endurance tests (pull-up) were performed. Body fat percentages for wrestlers in the 86-kg class or below were from 9.1% to 11.6%, whereas body fat percentages for wrestlers in the 92-, 97-, and 125-kg classes were 14.0 ± 3.5, 19.8 ± 6.9, and 26.6 ± 3.4%, respectively. This result suggests that the wrestlers in the heavier weight classes have a higher capacity to reduce body fat and increase muscle mass, which is essential if they improve strength and power. Absolute muscle strength and power performance tended to increase with heavier classes (the major results were as follows: 1RM bench press: 88.0 ± 13.0 kg in the 57-kg class and 142.0 ± 13.0 kg in the 125-kg class), whereas these relative values tended to decrease with heavier classes. Muscle endurance performance tended to decrease with heavier classes (the pull-up test: 23.8 ± 1.5 repetitions in the 61-kg class and 10.0 ± 5.4 repetitions in the 125-kg class). This study provides baseline data that can be used in the prescription of individual training programs for wrestlers, assessing areas of strength and weakness, and developing the wrestler's technical-tactical strategies.
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  • Yasuhisa Tachiya, Kiso Murakami, Hirokazu Arai, Masashi Uto, Takako Hi ...
    2020 Volume 6 Pages 44-61
    Published: 2020
    Released on J-STAGE: October 10, 2020
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    The purpose of this study was to develop an evaluation test of the psychological abilities required by Japanese elite athletes (such as national athletes). First, 11 elite athletes and coaches were interviewed to determine what they wanted to learn about the psychological factors of elite performance and what kinds of psychological testing they were willing to attempt. Second, based on the responses, we found 32 “psychological elements” required for elite athletes and used them to develop the survey questionnaire. Third, we gathered data from 824 university student-athletes regarding the psychological elements they felt were required for elite athletes and others from the survey. Among them, further analysis was specifically conducted with 194 elite athletes who either achieved a top eight ranking in a national tournament or had previous experiences in international tournaments. As a result, we were able to identify 10 psychological factors that are important for elite athletes: self-control, concentration, imagination, confidence, consistency, self-analysis, objective approaches, goal setting, motivation, and daily life management. Also, through further analysis based on competition levels, the study found that the higher the competition level of the participants, the higher their scores of 10 psychological factors. Through these findings, we developed a test that measures the psychological abilities required for elite athletes.
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  • Masae Yoshino, Nagisa Inoue, Takahiro Yoshizaki, Aya Ishibashi, Emi Ko ...
    2020 Volume 6 Pages 62-73
    Published: 2020
    Released on J-STAGE: October 10, 2020
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    Japan Institute of Sports Sciences routinely publishes information about supplements for athletes on its website. This information needs to be regularly updated based on athletes’ needs, the International Olympic Committee Consensus Statement, various health hazard reports, and evidence of performance-enhancing effects of supplements used by athletes. We investigated supplement use among 682 Japanese elite athletes who participated in the 2016 Rio de Janeiro Olympic Games. Supplement use was investigated based on a self-reported medical health questionnaire. We observed that 631 (92.5%) athletes used ≧1 supplements within the year prior to study enrollment. Amino acids were the most popular supplements consumed by 58.8% of athletes who admitted to supplement use. Recovery from fatigue was the most popular reason cited for supplement use. Among the athletes who used supplements, 57.4% received information regarding supplement use from their coaches, managers, and trainers, and 16.3% received information from healthcare professionals (i.e., physicians, pharmacists, and dietitians). Some athletes were unaware of the types of supplements that they used. A few athletes reported using supplements only because these products were being used by their teammates and admitted that their consumption of supplements was not meant for any particular purpose. This finding indicates that some athletes did not consider the necessity for and effects of supplements before using them. Therefore, athletes should have access to appropriate information regarding supplement use, including the rationale that justifies their consumption, as well as their effectiveness and safety to ensure judicious use of supplements in this population.
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  • Yuya Kimura, Toshiharu Yokozawa, Jun Yuda
    2020 Volume 6 Pages 74-87
    Published: 2020
    Released on J-STAGE: October 10, 2020
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    The purpose of this study was to identify the characteristics of female world-class skaters associated with the changes in skating speed and stroke parameters in the straight section for 3,000 m race in the speed skating international competition. Sixteen contestants were categorized into top (n=8) and second groups (n=8) according to the official records. The horizontal speeds of the end of the straight and curved sections of the skaters were recorded with the local position measurement system. In addition, 4 synchronized high-speed cameras (300 frames/s) were used to record the skaters' motions at the mid portion of the inner finishing straight lane in the initial phase (2nd or 3rd lap), middle phase (4th or 5th lap), and final phase (6th or 7th lap) and to calculate the skating velocity, stroke frequency, gliding time, push-off time, and stroke length. The skating velocity of the top group was significantly greater than that of the second group in each phase (p<0.001). In the middle phase, the skating velocity negatively correlated with stroke frequency (r=-0.53, p<0.05) and positively correlated with gliding time (r=0.62, p<0.01) and stroke length (r=0.71, p<0.01). In the final phase, the change in speed during the straight section positively correlated with stroke frequency (r=0.67, p<0.01), and negatively correlated with gliding time (r=-0.60, p<0.05) and stroke length (r=-0.64, p<0.01). The skaters who maintained large skating velocity in the middle phase would acquire a larger stroke length in the straight section by pushing-off the ice effectively. In the final phase, increasing the stroke frequency was important for suppression of the decrease in speed during the straight section.
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  • Yoshitaka Morishita, Munenori Murata
    2020 Volume 6 Pages 88-100
    Published: 2020
    Released on J-STAGE: October 10, 2020
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    In this study, we investigated the kinematic characteristics of various pitch types thrown by skilled softball pitchers. Nine female softball pitchers from the national Japanese softball team were requested to throw various pitch types that are used in competition and practice using the windmill style, while a three-dimensional motion capture system consisting of 20 infrared cameras (500 Hz) recorded reflective markers attached to the ball. The kinematic characteristics, such as the ball speed, spin rate, and direction of spin axis (angular velocity vector) were calculated from the measured coordinate values. The types of pitches (fastball, riseball, drop, and changeup) thrown by more than 5 pitchers were analyzed. The spin axes of all the analyzed trials were mostly oriented in the direction of the ball and upwards. The average ball speed of the fastball pitched by all pitchers had the highest, and in the case of the right-handed pitcher, the displacement of flight trajectory on the home plate changed by approximately 0.17 m downward and 0.06 m toward the left-handed batter under the influence of the lift force, as compared to that of the balls that were projected without rotation. Furthermore, when the flight trajectories of other pitch types were compared with that of fastball, the riseball, drop, and changeup types were shown to change in the upward, downward, and upper left directions, respectively. Our findings can be used as a guide to develop new pitch types or improve those that are currently employed in the game.
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  • Shuhei Yamashita
    2020 Volume 6 Pages 101-108
    Published: 2020
    Released on J-STAGE: October 10, 2020
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    The world is currently struggling with the global health emergency of COVID-19 (coronavirus disease 2019). The COVID-19 pandemic has put a halt to numerous high-performance sport activities; in particular, the Tokyo 2020 Olympic and Paralympic Games have been postponed until 2021. As the United Nations has pointed out, the actions that countries take now in response to the spread and impact of COVID-19 will be fundamental to a fair and sustainable transition to a new social contract in the years ahead. Thus, it is time to transform the “Old Normal” into the “New Normal” in a variety of fields, and high-performance sports is no exception. We aim to summarize what is important when seeking to determine how COVID-19 will impact high-performance sports and to discuss the challenges of high-performance sports in the “New Normal.” There is concern about the impact of COVID-19 on the mental health of elite athletes and the loss of opportunities for competition in the pathways of athlete development. In conclusion, athletes, coaches, and stakeholders in high-performance sports will compete to quickly adapt to the “New Normal” when high-performance sports activities restart. As COVID-19 could fundamentally change our approach to high-performance sports in the future, this issue requires further analysis.
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  • Yasuhiro Suzuki, Eiko Suzuki, Natsumi Chiba, Norie Nishimura, Saeko Ta ...
    2020 Volume 6 Pages 109-117
    Published: 2020
    Released on J-STAGE: November 14, 2020
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    When athletes are injured, various physical parameters decline due to the difficulty in maintaining the training volume and intensity. Among such physical factors, maintenance and improvement of aerobic fitness is considered to be one of the top priorities that the athlete must maintain or improve on in order to return to competition. The High Performance Gym (HPG) at the Japan Institute of Sports Sciences (JISS) conduct exercise training with the aim to improve aerobic capacity of athletes in rehabilitation phase. The purpose of this study was to analyze the data obtained from endurance training in athletes undergoing rehabilitation and to determine the duration and amount of training required to enhance their aerobic capacity. Twelve Japanese elite athletes underwent endurance training used by electronic-braked cycle ergometer in 2 sessions per day, each session lasting for 30 minutes with a rest interval of 5 minutes between the sessions. The athletes trained for 3-4 times per week a fixed period of time. The lactate curve test was applied before and after the training in order to determine the training load-value, and to validate the effectiveness of the endurance training. The average power at the lactate threshold (LT2) level increased by 23.8%, and the average power at the onset of blood lactate accumulation (OBLA) also increased by 16.4%. In addition, there was a significant correlation between the amount of the training and the rate of increase of average power at the LT2 level. These results indicate that an appropriate amount of endurance training could be employed based on the improvement ratio aimed by athletes.
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  • a case report of support in 2020 Australian Open
    Takashi Naito, Tatsuya Saito, Takahiko Tajima, Shunichi Someya, Toshih ...
    2020 Volume 6 Pages 118-128
    Published: 2020
    Released on J-STAGE: November 14, 2020
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    Among the tennis Grand Slam tournaments, the greatest number of heat-related health problems has occurred at the Australian Open. Previous studies showed that body cooling is effective strategy to prevent hyperthermia, in turn improving exercise performance in hot conditions. However, when support person provides athletes body cooling in tennis competition, no specific maneuver such as freezing cooling materials outside laboratory or transporting them to stadium is shown. The purpose of this paper was to investigate the strategies of support using body cooling in tennis competition according to case-based support in 2020 Australian Open. This article addresses the practical maneuvers of support using body cooling in tennis competition, as well as discussing the problems of freezing cooling materials outside laboratory or transporting them to stadium, and providing practical recommendations to optimize their success.
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  • Hideto Kato, Yui Shimada, Saeko Takahashi, Kosuke Nakazato, Yosuke Kid ...
    2020 Volume 6 Pages 129-138
    Published: 2020
    Released on J-STAGE: November 14, 2020
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    Skiing is associated with a high incidence of anterior cruciate ligament (ACL) injury. A higher incidence of ACL injuries in female skiers has been reported, similar to that in other sports; a previous study also reported a higher incidence of ACL injury in junior female skiers. Dynamic alignment of the leg is considered a risk factor for ACL injury. However, no reports have examined sex-related differences in dynamic alignment of junior athletes. Therefore, this study aimed to investigate the sex-related differences in dynamic alignment of the lower extremities as a risk factor for ACL injury in national top-level junior skiers. In total, 52 legs of 26 skiers (28 legs of 14 male junior skiers and 24 legs of 12 female junior skiers) were evaluated. The skiers performed drop vertical jump (DVJ) and single-leg squat (SLS). Frontal, sagittal, and horizontal plane images of their posture during DVJ and SLS were obtained. From these images, the joint angles of the lower extremities in the frontal and sagittal planes were calculated. The knee valgus angle at DVJ and SLS was significantly greater in female junior skiers than in males (p<0.001 and p<0.05, respectively). As knee valgus is a risk factor for ACL injury, dynamic alignment of junior female skiers seems to be improved to prevent ACL injury.
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  • Toshiharu Yokozawa, Fuminori Saikawa, Daisuke Kumagawa
    2020 Volume 6 Pages 139-151
    Published: 2020
    Released on J-STAGE: November 14, 2020
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    Although the record of speed skating has improved worldwide in recent years, the analysis of skating techniques at the international competitions has not progressed. The purpose of this study was to identify the skating technique of the world's leading male speed skaters during the curve of the track in a 1,500-m race. Thirteen skaters who participated in the men's 1,500-m race for the World Cup were selected, including the medalists in the race. Skating motion during the inner curve at the second or third lap was captured using 3 high-speed video cameras. The three-dimensional coordinates of the body were used to calculate the angles of the lower limb joints, the positional relationship between the body center of mass (CM) and the blades, and the heel elevation angle at the instant of the blade-off. All the parameters were analyzed for the correlation with the official time, and the velocity averaged in the section. In result, the characteristics of skaters who held better official time and higher section velocity were as follows: 1) the angular displacement of the right ankle dorsiflexion during gliding was smaller, 2) the angular displacement of the right hip extension and ankle plantarflexion during the push-off and the right heel elevation angle at the instant of the blade-off were smaller, 3) the direction of the right blade horizontal velocity vector was more consistent with that of the CM vector during the right stroke, and 4) the backward displacement of the blade relative to the CM during the right stroke was smaller. These results suggested that in the 1,500-m race the right stroke motion of the world's leading male skater was efficient and easy way to obtain a large centripetal force.
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  • Takuya Yanaka, Kenichiro Kawata, Takanori Kono, Yusuke Ishige
    2020 Volume 6 Pages 152-166
    Published: 2020
    Released on J-STAGE: January 06, 2021
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    The purpose of this study was to show the tendency of cross-country skiing in Nordic Combined competitions and to discuss the difference in speed between Japanese players and winners within eighth rank based on the physical characteristics of Japanese players. The fourteen 10 km races in 2018-2019 season were analyzed. Overall finish times and transit times for winners and 4 Japanese players were retrieved from official Home page of Fédération Internationale de Ski, and the segment times among the various points were calculated. Average segment speeds were calculated by dividing the segment distance by the segment time. For each race, the speed differences between winners’ average speed and Japanese players’ one was calculated. The subjects performed two exercise tests on different days. First, subjects performed multistage incremental roller-ski test to measure blood lactate concentration (La) and maximum oxygen uptake (VO2max). In another day, they performed roller-skiing on the treadmill where the speed and slope were changed assuming a 10 km race, and the La at the time was measured. In many of the 10km cross-country skiing races at the Nordic Combined, the winners skated at a fast speed in the early stages, narrowing the time difference from the beginning. Furthermore, it was shown that the speed of winners increased in last lap. The top Japanese player, who have won many prizes, was skating at the same speed as the winners, but other players were skating at a slower speed than the winners from the beginning of the race, which was the most prominent on the final lap (p < 0.01). Even though the top Japanese player’s VO2max (65 ml/kg/min) was lower than other players, the indicator showing gliding efficiency was highest (VVO2max: 5.5 m/s). These results suggest that the top Japanese player use energy-efficient gliding methods to suit various situations.
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  • Consideration from the influence of the WHO on sport in the case of COVID-19
    Takeshi Kukidome, Yoriko Noguchi
    2020 Volume 6 Pages 174-188
    Published: 2020
    Released on J-STAGE: January 06, 2021
    JOURNAL OPEN ACCESS
    The purpose of this research was to consider the possibility for the development of evidence-based policy making (EBPM) in the field of sport through the case of Coronavirus disease 2019 (COVID-19). COVID-19, originated in Wuhan, China, has rapidly spread world-wide and severely impacted society in several fields. High performance sport is no exception. The Tokyo 2020 Games, professional leagues and many competitions had to be suspended or postponed. Most of the training centers around the world partially or completely closed to protect athletes’ health and safety. Furthermore, restrictions of public life such as quarantine affected the physical and psychological conditioning of athletes. The planning and preparation to return to sport activities was therefore considered extremely important. The International Olympic Committee (IOC) developed a strategic partnership with the World Health Organization (WHO) to provide evidence-based information and advice to sports organizations. WHO published sport-specific guidelines and the IOC encouraged International Federations (Ifs) to follow WHO’s guidance. With the establishment of R&D Blueprint in 2016, the WHO is in a position to coordinate a global coalition of experts to accelerate the R&D process which develops new norms and standards during epidemics such as COVID-19. On one hand, various sporting organizations (government agencies, training centers, Olympic and Paralympic Committees), collaborated and shared information for decision-making. There was, however, concern for the lack of research-based evidence. The experience of COVID-19 showcased the importance to prepare and plan for the future based on evidence generated through research. Until now, evidence-based policy making (EBPM) has been rarely discussed in the field of sport. The High Performance Sport Center (HPSC) is the only one organization that owns a database storing various information related to sport in Japan, and therefore has the potential to foster the implementation of EBPM in the field of sport by utilizing its database.
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