Japan Institute of Sports science

Kita-ku, Japan

Japan Institute of Sports science

Kita-ku, Japan

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Shiose K.,Japan Institute of Sports science
Japanese Journal of Physical Fitness and Sports Medicine | Year: 2017

Carbohydrate is a crucial energy fuel for exercise, and carbohydrate supplementation as peri-exercise has beneficial effects on exercise performance. However, recent studies have indicated the possibility that periodized carbohydrate restriction improves exercise performance. Carbohydrate restriction before exercise increases fatty-acid oxidation (FAO) and alternatively prevents carbohydrate consumption during exercise. This may contribute to the prevention of muscle glycogen depletion during endurance exercise competition. Additionally, acute and chronic studies have shown that peri-exercise carbohydrate restriction enhances molecular and functional adaptation related to FAO. Similarly, exercise training in a low-muscle glycogen state accompanied by carbohydrate restriction was reported to enhance mitochondrial biogenesis and improve FAO capacity, aerobic capacity, and endurance performance in untrained and highly trained subjects. The potential mechanism of these metabolic adaptations may be related to elevated circulating fatty-acid and adrenaline concentration during exercise with carbohydrate restriction and/or a low-muscle glycogen state. In addition, a decrease in muscle glycogen content may trigger signaling pathways related to FAO and mitochondria biogenesis by activating proteins with a glycogen-binding domain. This article reviews the effects of exercise with carbohydrate restriction and/or low-muscle glycogen state on metabolic adaptation and exercise performance and describes the molecular mechanisms and availability.


Akagi R.,Shibaura Institute of Technology | Akagi R.,Japan Institute of Sports science | Takahashi H.,Japan Institute of Sports science
Scandinavian Journal of Medicine and Science in Sports | Year: 2014

This study investigated the effects of a static stretching (SS) program on muscle hardnesses of the gastrocnemius medialis (MG) and gastrocnemius lateralis (LG). Nineteen young men participated in this study. Either the right or left leg was randomly selected to conduct three bouts of 2-min SS of the plantar flexors 6 days a week for 5 weeks in each subject (the SS group), and the other leg was assigned to a control group. Before (pretest) and after (posttest) conducting the SS program, MG and LG hardnesses were measured using shear wave ultrasound elastography. The SS program was found to decrease muscle hardnesses, but not to change the ratio of MG hardness to LG hardness. There were no significant differences between the relative changes in the MG and LG hardnesses from pretest to posttest in both the SS and control groups. Significant correlations between the muscle hardness ratios at pretest and posttest were found in both groups. The results of this study suggest that the current SS program is useful for improving muscle condition in the plantar flexors, and that its long-term effects on the MG and LG hardnesses are of the same degree. © 2013 John Wiley & Sons A/S.


Hirayama K.,Waseda University | Hirayama K.,Japan Institute of Sports science
Journal of Strength and Conditioning Research | Year: 2014

The purpose of this study was to examine the acute effects of an ascending intensity squat protocol consisting of single-repetition exercises on subsequent vertical jump performance. Fourteen college weightlifters attended 2 testing sessions: squat (SQ) and control (CON) conditions. In the SQ condition, squat exercises with incremental loads (20% 1 repetition maximum [RM], 40% 1RM, 60% 1RM, 80% 1RM, and maximal isometric [MI] half-squat exercise) were performed with a time interval of 3 minutes after submaximal cycling and static stretching. Maximum vertical jump height was measured at the beginning of the session and after cycling, static stretching, and each squat exercise in the SQ condition. In the CON condition, vertical jump height was measured at the same times with the subject resting on a chair after cycling and stretching. Vertical jump height gradually increased after 60% 1RM, 80% 1RM, and MI half-squat exercises compared with baseline values (i.e., first trial of vertical jump), whereas no change was observed in the CON condition. These results suggest that an ascending intensity squat protocol consisting of single-repetition exercises of sufficient intensity can be useful for athletes who require high muscular power. © 2014 National Strength and Conditioning Association.


Arakawa H.,Japan Institute of Sports science
Journal of applied biomechanics | Year: 2013

The current study aimed to investigate the effect of ankle restriction on the coordination of vertical jumping and discuss the influence of energy transfer through m. gastrocnemius on the multijoint movement. Eight participants performed two types of vertical jumps: a normal squat jump, and a squat jump with restricted ankle joint movement. Mechanical outputs were calculated using an inverse dynamics analysis. Custom-made shoes were used to restrict plantar flexion, resulting in significantly (P < .001) reduced maximum power and work at the ankle joint to below 2% and 3%, while maintaining natural range of motion at the hip and knee. Based on the comparison between the two types of jumps, we determined that the ankle restriction increased (P < .001) the power (827 ± 346 W vs. 1276 ± 326 W) and work (92 ± 34 J vs. 144 ± 36 J) at the knee joint. A large part of the enhanced output at the knee is assumed to be due to ankle restriction, which results in the nullification of energy transport via m. gastrocnemius; that is, reduced contribution of the energy transfer with ankle restriction appeared as augmentation at the knee joint.


Harrison C.B.,University of Auckland | Gill N.D.,University of Auckland | Kinugasa T.,Japan Institute of Sports science | Kilding A.E.,University of Auckland
Sports Medicine | Year: 2015

The importance of a high level of aerobic fitness for team sport players is well known. Previous research suggests that aerobic fitness can be effectively increased in adults using traditional aerobic conditioning methods, including high-intensity interval and moderate-intensity continuous training, or more recent game-based conditioning that involves movement and skill-specific tasks, e.g. small-sided games. However, aerobic fitness training for youth team sport players has received limited attention and is likely to differ from that for adults due to changes in maturation. Given young athletes experience different rates of maturation and technical skill development, the most appropriate aerobic fitness training modes and loading parameters are likely to be specific to the developmental stage of a player. Therefore, we analysed studies that investigated exercise protocols to enhance aerobic fitness in young athletes, relative to growth and maturation, to determine current best practice and limitations. Findings were subsequently used to guide an evidence-based model for aerobic fitness development. During the sampling stage (exploration of multiple sports), regular participation in moderate-intensity aerobic fitness training, integrated into sport-specific drills, activities and skill-based games, is recommended. During the specialisation stage (increased commitment to a chosen sport), high-intensity small-sided games should be prioritised to provide the simultaneous development of aerobic fitness and technical skills. Once players enter the investment stage (pursuit of proficiency in a chosen sport), a combination of small-sided games and high-intensity interval training is recommended. © 2015, Springer International Publishing Switzerland.


Akagi R.,Japan Institute of Sports science | Tohdoh Y.,Japan Institute of Sports science | Takahashi H.,Japan Institute of Sports science
International Journal of Sports Medicine | Year: 2013

This study compared strength and size of reciprocal muscle groups in the lower leg between sexes. 20 young men and 14 young women volunteered as subjects. Joint torques developed during isometric maximal voluntary plantar flexion (TQPF) and dorsiflexion (TQDF) were measured using a dynamometer. Muscle volumes of plantar flexors (MVPF) and dorsiflexors (MVDF) were determined by magnetic resonance imaging. In each of the muscle groups, joint torque was significantly correlated with muscle volume in young men and women (r=0.610-0.848) and the y-intercept of the regression line between them was not significantly different from zero. Based on these observations, the dependencies of muscle strength ratio on muscle size ratio between the plantar flexors and dorsiflexors were investigated using joint torque and muscle volume. The correlations between the MVPF per MVDF and the TQPF per TQDF were significant both in young men (r=0.608) and women (r=0.773), suggesting that strength ratio is strongly affected by size ratio between the plantar flexors and dorsiflexors in young men and women. © Georg Thieme Verlag KG Stuttgart · New York.


Miyaji C.,Japan Institute of Sports Science
Advances in Intelligent Systems and Computing | Year: 2016

Although frame-by-frame is one of the important operation to see sports movement precisely, it is not implemented in the streaming videos on the Internet. This article introduces Smart-method, a new method of frame-byframe on the streaming videos. It is based on the combination of two methods, streaming and download; streaming is used for playback, the image download is used for frame-by-frame operation, and these operations are switched smoothly, users will not notice these switches. Smart-method is not only enables to see sports movement precisely it opens various applications possible on the Internet; attaching meta-data of the sports videos, flexible thumbnail, and editing (cut and join the videos) on the Internet. © Springer International Publishing Switzerland 2016.


Kawamori N.,Edith Cowan University | Kawamori N.,Japan Institute of Sports science | Nosaka K.,Edith Cowan University | Newton R.U.,Edith Cowan University
Journal of Strength and Conditioning Research | Year: 2013

Kawamori, N, Nosaka, K, and Newton, RU. Relationships between ground reaction impulse and sprint acceleration performance in team sport athletes. J Strength Cond Res 27(3): 568-573, 2013-Large horizontal acceleration in short sprints is a critical performance parameter for many team sport athletes. It is often stated that producing large horizontal impulse at each ground contact is essential for high short sprint performance, but the optimal pattern of horizontal and vertical impulses is not well understood, especially when the sprints are initiated from a standing start. This study was an investigation of the relationships between ground reaction impulses and sprint acceleration performance from a standing start in team sport athletes. Thirty physically active young men with team sport background performed 10-m sprint from a standing start, whereas sprint time and ground reaction forces were recorded during the first ground contact and at 8 m from the start. Associations between sprint time and ground reaction impulses (normalized to body mass) were determined by a Pearson's correlation coefficient (r) analysis. The 10-m sprint time was significantly (p < 0.01) correlated with net horizontal impulse (r = 20.52) and propulsive impulse (r = 20.66) measured at 8 m from the start. No significant correlations were found between sprint time and impulses recorded during the first ground contact after the start. These results suggest that applying ground reaction impulse in a more horizontal direction is important for sprint acceleration from a standing start. This is consistent with the hypothesis of training to increase net horizontal impulse production using sled towing or using elastic resistance devices, which needs to be validated by future longitudinal training studies. © 2013 National Strength and Conditioning Association.


Kon M.,Japan Institute of Sports science | Ikeda T.,Japan Institute of Sports science | Homma T.,Japan Institute of Sports science | Suzuki Y.,Japan Institute of Sports science
Journal of Strength and Conditioning Research | Year: 2012

Previous studies have shown that low-intensity resistance exercises with vascular occlusion and slow movement effectively increase muscular size and strength. Researchers have speculated that local hypoxia by occlusion and slow movement may contribute to such adaptations via promoting anabolic hormone secretions by the local accumulation of metabolites. In this study, we determined the effects of lowintensity resistance exercise under acute systemic hypoxia on metabolic and hormonal responses. Eight male subjects participated in 2 experimental trials: (a) low-intensity resistance exercise while breathing normoxic air (normoxic resistance exercise [NR]), (b) low-intensity resistance exercise while breathing 13% oxygen (hypoxic resistance exercise [HR]). The resistance exercises (bench press and leg press) consisted of 14 repetitions for 5 sets at 50% of maximum strength with 1 minute of rest between sets. Blood lactate (LA), serum growth hormone (GH), norepinephrine (NE), testosterone, and cortisol concentrations were measured before normoxia and hypoxia exposures; 15 minutes after the exposures; and at 0, 15, and 30 minutes after the exercises. The LA levels significantly increased after exercises in both trials (p ≤ 0.05). The area under the curve for LA after exercises was significantly higher in the HR trial than in the NR trial (p ≤ 0.05). The GH significantly increased only after the HR trial (p ≤ 0.05). The NE and testosterone significantly increased after the exercises in both trials (p≤ 0.05). Cortisol did not significantly change in both trials. These results suggest that low-intensity resistance exercise in the hypoxic condition caused greater metabolic and hormonal responses than that in the normoxic condition. Coaches may consider low-intensity resistance exercise under systemic hypoxia as a potential training method for athletes who need to maintain muscle mass and strength during the long in-season. © 2012 National Strength and Conditioning Association.


Akagi R.,Japan Institute of Sports science | Takahashi H.,Japan Institute of Sports science
Medicine and Science in Sports and Exercise | Year: 2013

PURPOSE: The objective of this study is to investigate the acute effects of static stretching (SS) on muscle hardness of the gastrocnemius medialis (MG) and gastrocnemius lateralis (LG). METHODS: Twenty young men participated in this study. MG and LG hardness was measured using shear wave ultrasound elastography before and after three bouts of 2-min SS. The measurement site of muscle hardness was at 30% of the lower leg length from the popliteal crease to the lateral malleolus. Similarly, the passive range of motion (ROM) of dorsiflexion, musculotendinous unit (MTU) stiffness determined by the slope of the portion of the passive torque-angle curve from 15 to 25 , and joint torque developed during isometric maximal voluntary plantarflexion at 0 of ankle joint angle were also measured before and after SS. RESULTS: SS increased ROM and decreased MTU stiffness significantly but did not change joint torque. The main effects of test time and muscle group on muscle hardness were significant without a significant interaction of these variables. Both differences between the relative changes in the MG and LG hardness and between the muscle hardness ratios before and after SS were not significant. A significant correlation between the muscle hardness ratios before and after SS was found. CONCLUSION: The results of this study suggest that three bouts of 2-min SS of the plantar flexors is useful for preventing muscle injury, improving muscle condition, and maintaining muscle strength, and that the acute effects of SS on the muscle hardness of MG and LG are of the same degree. Copyright © 2013 by the American College of Sports Medicine.

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