Japanese Journal of Physical Fitness and Sports Medicine
Online ISSN : 1881-4751
Print ISSN : 0039-906X
ISSN-L : 0039-906X
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Showing 1-9 articles out of 9 articles from the selected issue
Review
  • Masamichi Yamamoto
    Type: Review
    2019 Volume 68 Issue 4 Pages 245-249
    Published: August 01, 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

    Muscle contraction requires energy. However, the dynamics of adenosine triphosphate (ATP) in the skeletal muscle contraction in vivo is unknown. Therefore, we tried to visualize ATP dynamics in mice. By performing various gene modifications using Goateam reported as FRET-type fluorescent protein that senses ATP, we succeeded in creating a mouse that can visualize ATP level in the cytoplasm. By resting the skeletal muscle of this mouse from contraction exercise, it succeeded in capturing in vivo the decrease in the amount of ATP by exercise and the recovery of the amount of ATP by rest. This mouse can be used to evaluate muscle movement in vivo by ATP dynamics.

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Original
  • Miki Eto, Hiroyuki Sasai, Takehiko Tsujimoto, Rina So, Kiyoji Tanaka
    Type: Original
    2019 Volume 68 Issue 4 Pages 251-259
    Published: August 01, 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

    This study described 1-year changes in body weight and metabolic syndrome components in middle-aged obese Japanese men participating in a 6-month weight loss program. This study comprised two phases: 6-month weight loss program and 12-month weight maintenance. Data were collected at Tsukuba, between July 2009 and February 2011. Overweight or obese Japanese men aged 40-64 years without any cardiovascular disease history participated. The primary outcome was the 18-month weight change. Secondary outcomes were 18-month changes in metabolic syndrome components. Primary analyses included all participants who had provided baseline data, and all missing follow-up values were replaced with their baseline data. Of the 58 participants, 39 (67.2%) completed all measurement visits. Their body weight decreased significantly immediately after the 6-month weight loss program (-8.0 kg; 95% confidence interval [CI]: -10.2 kg, -5.8 kg). However, it increased significantly, by 3.7 kg (95% CI: 1.4 kg, 6.0 kg), at Month 18 (a year after the program ended). The 18-month weight loss was 4.3 kg (95% CI: 2.1 kg, 6.5 kg). Among the metabolic syndrome components, visceral fat area, systolic blood pressure, and high-density lipoprotein cholesterol levels improved significantly at Month 18. The other components did not improve over the 18 months. In this study, the obese, middle-aged Japanese men experienced modest weight regains after its substantial reduction. Unlike other ethnicities, factors associated with long-term weight loss maintenance remain understudied among Japanese adults. Therefore, accumulating evidence from Japanese studies with longer follow-up is necessary in the future.

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  • Yumiko Onodera, Naruki Kitano, Tsutomu Kuchiki, Yuko Kai, Toshiya Naga ...
    Type: Original
    2019 Volume 68 Issue 4 Pages 261-268
    Published: August 01, 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

    In this study, we performed isotemporal substitution analysis to examine potential associations of sedentary time and physical activity with mental health of Japanese office workers. This study employed a cross-sectional study design. We analyzed data on 108 Japanese office workers (mean age 46.4 ± 9.8 years; 64.8% women) in the study. Sedentary behavior (SB; ≤ 1.5 metabolic equivalents [METs]), light-intensity physical activity (LPA; 1.6–2.9 METs), and moderate-to-vigorous physical activity (MVPA; ≥ 3 METs) were measured with a triaxial accelerometer. Two kinds of self-administered questionnaires, the mental stress (K6) and work engagement (Utrecht Work Engagement Scale), were used to assess negative/positive mental health. A cut-off score of 5 or higher on the K6 was used to define persons with mental stress. Logistic and multiple regression analyses using an isotemporal substitution model was applied to demonstrate the association between replacing 30 min/d of SB with an equal amount of time spent on LPA or MVPA and mental stress and work engagement; the studied covariates were age, sex, body mass index, economic status, education, and overtime hours. The results showed that replacing SB with MVPA for 30 min/d was significantly decreased odds ratio (OR) of mental stress (OR = 0.38, 95% confidence interval 0.15–0.92), whereas the replacement was not associated with work engagement (B = 0.16, P = 0.38). In contrast, substitution of SB with LPA was not associated with mental stress and work engagement. These results indicate that substituting sedentary time with MVPA could be associated with mental stress of Japanese office workers.

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  • Takamasa Mizuno
    Type: Original
    2019 Volume 68 Issue 4 Pages 269-277
    Published: August 01, 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

    This study aimed to examine the effects of different voluntary forces of dynamic stretching (DS) on the maximal dorsiflexion angle of the ankle joint, passive torque, and subjective fatigue. Eleven healthy male participants were included in this study. Ankle angle and passive torque were measured before and after DS, which involved four sets of ankle plantarflexion-dorsiflexion performed for 30 s while sitting on an isokinetic machine with the knees fully extended. Although ankle plantarflexion was passively performed via an isokinetic machine, participants were instructed to perform the active ankle dorsiflexion under either of the following two conditions: with maximal voluntary contraction (MVC) (DSmax) or with submaximal voluntary contraction (DSsub). In DSsub, 80% MVC was set as the target voluntary force. Subjective fatigue during DS was measured using the visual analogue scale. In DSsub, participants actually demonstrated 87.0 ± 5.8% MVC. The maximal ankle dorsiflexion angle significantly increased after DS in both conditions. Subjective fatigue was significantly greater after two, three, and four sets of DSmax than after the corresponding repetitions of DSsub. Although passive torque at the maximal dorsiflexion angle tended to increase after stretching, no significant changes were observed in the passive torque from before to after DS. These results compared MVC with approximately 87% MVC, indicating that the voluntary force of DS did not influence the increment of the maximal dorsiflexion angle after DS. Our study findings also suggested that 80–90% MVC is recommended during DS to increase the maximal dorsiflexion angle without excessive subjective fatigue.

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