著者

Yudai Takarada Tomomi Tsuruta Naokata Ishii

出版者

日本生理学会

雑誌

The Japanese Journal of Physiology (ISSN:0021521X)

巻号頁・発行日

vol.54, no.6, pp.585-592, 2004 (Released:2005-03-12)

参考文献数

36

被引用文献数

56 120

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To obtain insight into the relative contributions of exercise and occlusive stimuli to these muscular adaptations, the present study investigated the short- and long-term effects of varied combinations of low- intensity exercise and vascular occlusion. The subjects were separated into 3 groups (n = 6 for each group): low- intensity with vascular occlusion (LIO), low-intensity without vascular occlusion (LI), and vascular occlusion without exercise (VO). LIO and LI groups performed bilateral knee extension exercises in seated positions with an isotonic extension machine. In the LIO group, both sides of the thigh were pressure-occluded at the proximal end by means of a tourniquet during the entire session of exercise (˜10 min), whereas only the occlusion with the same pressure and duration was given in the VO group. The mean occlusion pressure was 218 ± 8.1 mmHg (mean ± SE). The exercise session consisted of five sets of exercise at an intensity of 10-20% 1RM and was performed twice a week for 8 wk. After the period of exercise training, isometric and isokinetic strengths at all velocities examined increased significantly in the LIO group (p < 0.05), whereas no significant change in strength was seen in the LI and VO groups. The increase in muscular strength in LIO was associated with a significant increase in the cross-sectional area of knee extensor muscles by 10.3 ± 1.6%. The plasma growth hormone concentration measured 15 min after the session of exercise showed a marked increase only in LIO. The results showed that the low-intensity exercise and occlusive stimuli have cooperative effects in the long-term adaptation of muscle and an acute response to growth hormone.

著者

Naokata Ishii Riki Ogasawara Koji Kobayashi Koichi Nakazato

出版者

一般社団法人日本体力医学会

雑誌

The Journal of Physical Fitness and Sports Medicine (ISSN:21868131)

巻号頁・発行日

vol.1, no.1, pp.83-94, 2012-05-25 (Released:2012-08-22)

参考文献数

118

被引用文献数

2 11 6

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To learn the mechanisms underlying resistance exercise-induced muscle hypertrophy, recent studies on muscle protein metabolism and myogenic progenitor cells were reviewed. Numerous studies have suggested that activation of the translation process plays a major role in a resistance exercise-induced increase in muscle protein synthesis, and also in muscle hypertrophy after a prolonged period of training. Among regulators of the translational activity, the mTORC1 signaling pathway has been shown to be important, although the relation between its upstream regulation and exercise regimen remains unclear. In addition, the muscle satellite cells play a part, even if not indispensable, in exercise-induced muscle hypertrophy, by supplying muscle fibers with new myonuclei. Middle to high exercise intensity has been regarded as essential for gaining muscle mass, because it causes the recruitment of large motor units with fast, type II muscle fibers, which are readily hypertrophied through activation of mTORC1 signaling. However, several studies have shown that low-intensity resistance exercises with either large exercise volume or prolonged contraction time effectively activate protein synthesis and induce muscle hypertrophy. These findings suggest that various strategies are possible in exercise regimens, and exercise intensity is not necessarily a primary factor for gaining muscular size.

著者

Takahisa Ohta Junzo Nagashima Wataru Fukuda Hiroyuki Sasai Naokata Ishii

出版者

Japan Epidemiological Association

雑誌

Journal of Epidemiology (ISSN:09175040)

巻号頁・発行日

vol.32, no.12, pp.543-550, 2022-12-05 (Released:2022-12-05)

参考文献数

39

被引用文献数

1

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Background: Knee extensor muscle strength and cardiorespiratory fitness (CRF) are major components of physical fitness. Because the interactive association of knee extensor muscle strength and CRF with bone health remains unclear, we aimed to investigate such association in Japanese adults.Methods: Altogether, 8,829 Japanese adults (3,731 men and 5,098 women) aged ≥45 years completed the maximum voluntary knee extension test, submaximal exercise test, medical examination, and a questionnaire on lifestyle habits. Using an osteo-sono assessment index, low bone stiffness tendency was defined as 80% under the young-adults mean. Multivariable odds ratios (ORs) and 95% confidence intervals (CIs) were calculated after confounder adjustment.Results: Overall, 542 men (14.5%) and 978 women (19.2%) had low bone stiffness tendency. We observed an inverse association between muscle strength and low bone stiffness tendency after adjustment for CRF in both sexes (P for linear trend <0.001). Compared with the lowest CRF, the multivariable ORs for low bone stiffness tendency in the highest CRF were 0.47 (95% CI, 0.36–0.62) for men and 1.05 (95% CI, 0.82–1.35) for post-menopausal women (P < 0.001 and P = 0.704, respectively). No interactive association between muscle strength and CRF for low bone stiffness tendency existed in both sexes and irrespective of menopausal status.Conclusion: Knee extensor muscle strength and CRF were associated additively, not synergistically, with bone health. Maintaining high levels of both physical fitness components may improve musculoskeletal health in the cohort. The relationship between physical fitness and bone status should be longitudinally investigated in the future.

著者

Sho Hatanaka Naokata Ishii

出版者

The Japanese Society of Physical Fitness and Sports Medicine

雑誌

The Journal of Physical Fitness and Sports Medicine (ISSN:21868131)

巻号頁・発行日

vol.11, no.5, pp.295-303, 2022-09-25 (Released:2022-09-13)

参考文献数

60

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This study conducted a secondary survey based on the hypothesis that the “total mechanical activation of fast-twitch fibers in the muscles determines the effects of muscle hypertrophy”, with resistance training of the knee extensor muscles as the target because of its importance in preventing sarcopenia. Using a mathematical model that estimates the mechanical activation of each muscle fiber (fast-twitch and slow-twitch fiber) during exercise, which was developed in a previous study, we estimated the total mechanical activation of fast-twitch fibers in 30 training programs described in 23 selected previous studies on leg extension exercise programs and their muscle hypertrophy effect. With the estimated value and other factors of the training effect described in previous studies (training volume, etc.) as explanatory variables and muscle hypertrophy effect as an objective variable, we performed multiple regression analysis. The results revealed that the training effect was related to total mechanical activation of the fast-twitch fibers (standardized partial regression coefficient: 0.66), training load (standardized partial regression coefficient, 0.29) and number of sets (standardized partial regression coefficient: −0.37). The total mechanical activation of fast-twitch fibers was the strongest determinant of the muscle hypertrophy effect. In addition, we predicted the relationship between the level of the training effect of leg extension exercise and program variables. This study is the first to demonstrate “the relationship between total mechanical activation of fast-twitch fibers and muscle hypertrophy effect” in the field of muscle physiology, and the first to elucidate the association between the program variables and the training effect.

著者

Takahisa Ohta Junzo Nagashima Wataru Fukuda Hiroyuki Sasai Naokata Ishii

出版者

Japan Epidemiological Association

雑誌

Journal of Epidemiology (ISSN:09175040)

巻号頁・発行日

pp.JE20200581, (Released:2021-04-10)

参考文献数

39

被引用文献数

1

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BackgroundKnee extensor muscle strength and cardiorespiratory fitness (CRF) are major components of physical fitness. Because the interactive association of knee extensor muscle strength and CRF with bone health remains unclear, we aimed to investigate such association in Japanese adults.MethodsAltogether, 8,829 Japanese adults (3,731 men and 5,098 women) aged ≥45 years completed the maximum voluntary knee extension test, submaximal exercise test, medical examination, and a questionnaire on lifestyle habits. Using an osteo-sono assessment index, low bone stiffness tendency was defined as 80% under the young-adults mean. Multivariable odds ratios (ORs) and 95% confidence intervals (CIs) were calculated after confounder adjustment.ResultsOverall, 542 men (14.5%) and 978 women (19.2%) had low bone stiffness tendency. We observed an inverse association between muscle strength and low bone stiffness tendency after adjustment for CRF in both sexes (p for linear trend < 0.001). Compared with the lowest CRF, the multivariable ORs (95% CI) for low bone stiffness tendency in the highest CRF were 0.47 (0.36, 0.62) for men and 1.05 (0.82, 1.35) for post-menopausal women (p < 0.001 and p = 0.704, respectively). No interactive association between muscle strength and CRF for low bone stiffness tendency existed in both sexes and irrespective of menopausal status.ConclusionKnee extensor muscle strength and CRF were associated additively, not synergistically, with bone health. Maintaining high levels of both physical fitness components may improve musculoskeletal health in the cohort. The relationship between physical fitness and bone status should be longitudinally investigated in the future.

著者

Eisuke Ochi Koichi Nakazato Naokata Ishii

出版者

日本生理学会

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.57, no.1, pp.1-6, 2007 (Released:2007-02-24)

参考文献数

36

被引用文献数

15 26

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We investigated the effects of repeated eccentric exercise for rat medial gastrocnemius muscle on ankle joint stiffness and muscle connectin (titin) isoform composition (longer form, α-connectin; shorter form, β-connectin). Male Wistar rats were trained on a custom-made, isokinetic dynamometer (eccentric-exercise group, n = 6; sham-operated group, n = 6). The exercise session consisted of 20 eccentric contractions elicited by submaximal electric stimulations under anesthesia. The contracting muscle was forcibly lengthened by an isokinetic dorsi-flexion of the ankle joint (velocity, 30°/s; range of motion, 45°). Rats in the eccentric-exercise group were trained every two days for 20 days (10 sessions in total). The static passive resistive torque (PRT) of 45° at the ankle joint was used as a measure of the joint stiffness, and was determined before and after the experimental period. After 10 sessions of eccentric exercise, the wet weight of medial gastrocnemius muscle significantly increased (P < 0.05), whereas the static PRT significantly decreased (P < 0.05) in the eccentric-exercise group, when compared to the sham-operated group. Myosin-ATPase staining showed a decrease in the number of type IIb/IId fibers (P < 0.001) and an increase in the number of type IIa fibers (P < 0.05). However, no significant difference was seen in the connectin (titin) isoform composition between the eccentric-exercise group and the sham-operated group, suggesting that the reduction in PRT was not due to change in resting mechanical properties of muscle fibers.

著者

Kazushige Goto Naokata Ishii Kaoru Takamatsu

出版者

Japan Society of Physical Education, Health and Sport Sciences

雑誌

International Journal of Sport and Health Science (ISSN:13481509)

巻号頁・発行日

vol.2, pp.111-118, 2004 (Released:2008-01-23)

参考文献数

25

被引用文献数

3 4 6

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We had previously shown that performing a single set of resistance exercise at 50% of 1 repetition maximum (RM) added after a high-intensity, low-repetition exercise (strength-type regimen) greatly enhanced growth hormone (GH) secretion [Goto et al. (2003)]. The present study aimed to investigate the effect of an additional set at 50% to 20% of 1RM after a strength-type regimen on anabolic hormone secretion. Eight male subjects performed bilateral knee extension exercises using a strength-type regimen (5 sets at 90% of 1RM, with 3-min rests), and other 3 types of regimens, in which 1 set of exercise at either 50%, 30% or 20% of 1RM was added immediately after the strength-type regimen (defined as C50-type, C30-type and C20-type regimens, respectively). Concentrations of serum GH, testosterone and blood lactate were measured before and after exercises. The number of repetitions in the added set showed a significant dependence on the exercise intensity: 82.3 times in C20-type > 46.1 times in C30-type > 22.6 times in C50-type (p ≤ 0.05). Post-exercise GH concentrations were significantly (p ≤ 0.05) higher in C50- and C30-type regimens than in the strength-type regimen, whereas no significant difference was observed between C20- and strength-type regimens. Testosterone did not change in any types of regimen. These results indicated that performing a single set of exercise at low intensity added after a strength-type regimen caused a significant increase in GH concentration. However, such an effect might be diminished when the intensity of the additional exercise was extremely low (below 20% of 1RM).