Noriteru Morita

Intramuscular metabolism during low-intensity resistance exercise with blood flow restriction

Although recent studies have reported that low-intensity resistance training with blood flow restriction could stress the muscle effectively and provide rapid muscle hypertrophy and strength gain equivalent to those of high-intensity resistance training, the exact mechanism and its generality have not yet been clarified. We investigated the intramuscular metabolism during low-intensity resistance exercise with blood flow restriction and compared it with that of high-intensity and low-intensity resistance exercises without blood flow restriction using (31)P-magnetic resonance spectroscopy. Twenty-six healthy subjects (22 +/- 4 yr) participated and performed unilateral plantar flexion (30 repetitions/min) for 2 min. Protocols were as follows: low-intensity exercise (L) using a load of 20% of one-repetition maximum (1 RM), L with blood flow restriction (LR), and high-intensity exercise using 65% 1 RM (H). Intramuscular phosphocreatine (PCr) and diprotonated phosphate (H(2)PO(4)(-)) levels and intramuscular pH at rest and during exercise were obtained. We found that the PCr depletion, the H(2)PO(4)(-) increase, and the intramuscular pH decrease during LR were significantly greater than those in L (P < 0.001); however, those in LR were significantly lower than those in H (P < 0.001). The recruitment of fast-twitch fiber evaluated by inorganic phosphate splitting occurred in only 31% of the subjects in LR, compared with 70% in H. In conclusion, the metabolic stress in skeletal muscle during low-intensity resistance exercise was significantly increased by applying blood flow restriction, but did not generally reach that during high-intensity resistance exercise. This new method of resistance training needs to be examined for optimization of the protocol to reach equivalence with high-intensity resistance training.

Dose effect on intramuscular metabolic stress during low-intensity resistance exercise with blood flow restriction

Our previous study reported that metabolic stress in skeletal muscle achieved by combining moderate blood flow restriction (BFR) with low-intensity resistance exercise at 20% of one repetition maximum (1 RM) could not reach the level achieved by high-intensity resistance exercise. Since the previous protocol is typical of current regimens of this type, we sought in this study to optimize the exercise protocol for low-intensity resistance exercise with BFR by examining the dose effects of exercise intensity and pressure. Twelve healthy subjects participated in this study. They were asked to perform unilateral plantar flexion for 2 min (30 repetitions/min) under six different conditions: two resistance exercises (20% 1 RM and 65% 1 RM) without BFR, and four BFR protocols. The four BFR protocols included three different exercise intensities (20, 30, and 40% 1 RM) with moderate pressure (MP) using 130% of systolic blood pressure (147+/-17 mmHg, mean+/-SD) and 20% 1 RM with high pressure at 200 mmHg. Intramuscular metabolites and pH were obtained by 31P-magnetic resonance spectroscopy. Significant dose effects on intramuscular metabolites and pH were observed for exercise intensity (P<0.001) but not for BFR pressure. The BFR protocol combining 30% 1 RM with MP had similar results as the high-intensity load at 65% 1 RM. Intramuscular metabolic stress during BFR exercise might be susceptible to increasing exercise intensity. To replace high-intensity resistance exercise, the BFR protocol might require an intensity of >or=30% 1 RM.

Low-intensity exercise can increase muscle mass and strength proportionally to enhanced metabolic stress under ischemic conditions

Skeletal muscle bulk and strength are becoming important therapeutic targets in medicine. To increase muscle mass, however, intensive, long-term mechanical stress must be applied to the muscles, and such stress is often accompanied by orthopedic and cardiovascular problems. We examined the effects of circulatory occlusion in resistance training combined with a very low-intensity mechanical load on enhancing muscular metabolic stress and thereby increasing muscle bulk. Muscular metabolic stress, as indicated by the increases in inorganic phosphate (P(i)) and a decrease in intramuscular pH, was evaluated by (31)P-magnetic resonance spectroscopy during unilateral plantar-flexion at 20% of the one-repetition maximum (1-RM) with circulatory occlusion for 2 min in 14 healthy, male untrained participants (22 yr) at baseline. Participants performed two sets of the same exercise with a 30-s rest between sets, 2 times/day, 3 days/wk, for 4 wk. The muscle cross-sectional area (MCA) of the plantar-flexors and the 1-RM were measured at baseline and after 2 and 4 wk of training. MCA and 1-RM were significantly increased after 2 and 4 wk (P < 0.05, respectively). The increase in MCA at 2 wk was significantly (P < 0.05) correlated with the changes in P(i) (r = 0.876) and intramuscular pH (r = 0.601). Furthermore, the increases in MCA at 4 wk and 1-RM at 2 wk were also correlated with the metabolic stress. Thus enhanced metabolic stress in exercising muscle is a key mechanism for favorable effects by resistance training. Low-intensity resistance exercise provides successful outcomes when performed with circulatory occlusion, even with a short training period.

Systemic Oxidative Stress Is Associated With Lower Aerobic Capacity and Impaired Skeletal Muscle Energy Metabolism in Patients With Metabolic Syndrome

OBJECTIVE Systemic oxidative stress is associated with insulin resistance and obesity. We tested the hypothesis that systemic oxidative stress is linked to lower aerobic capacity and skeletal muscle dysfunction in metabolic syndrome (MetS). RESEARCH DESIGN AND METHODS The incremental exercise testing with cycle ergometer was performed in 14 male patients with MetS and 13 age-, sex-, and activity-matched healthy subjects. Systemic lipid peroxidation was assessed by serum thiobarbituric acid reactive substances (TBARS), and systemic antioxidant defense capacity was assessed by serum total thiols and enzymatic activity of superoxide dismutase (SOD). To assess skeletal muscle energy metabolism, we measured high-energy phosphates in the calf muscle during plantar flexion exercise and intramyocellular lipid (IMCL) in the resting leg muscle, using 31P- and 1proton-magnetic resonance spectroscopy, respectively. RESULTS Serum TBARS were elevated (12.4 ± 7.1 vs. 3.7 ± 1.1 μmol/L; P < 0.01), and serum total thiols and SOD activity were decreased (290.8 ± 51.2 vs. 398.7 ± 105.2 μmol/L, P < 0.01; and 22.2 ± 8.4 vs. 31.5 ± 8.5 units/L, P < 0.05, respectively) in patients with MetS compared with healthy subjects. Peak VO2 and anaerobic threshold normalized to body weight were significantly lower in MetS patients by 25 and 31%, respectively, and inversely correlated with serum TBARS (r = −0.49 and r = −0.50, respectively). Moreover, muscle phosphocreatine loss during exercise was 1.4-fold greater in patients with MetS (P < 0.05), and IMCL content was 2.9-fold higher in patients with MetS (P < 0.01), indicating impaired skeletal muscle energy metabolism, and these indices positively correlated with serum TBARS (r = 0.45 and r = 0.63, respectively). CONCLUSIONS Systemic oxidative stress was associated with lower aerobic capacity and impaired skeletal muscle energy metabolism in patients with MetS.

Toe flexor strength and foot arch height in children.

PURPOSE The aim of this study was to investigate the muscle strength and arch height of the foot in the standing position and the relations between these indices and physical performances involving the lower limbs in children. METHODS A total of 301 elementary school children (third grade: n = 158, age = 8.6 ± 0.5 yr; fifth grade: n = 143, age = 10.6 ± 0.5 yr; means ± SD) participated. The maximal isometric toe flexor strength (TFS) in the standing position was measured using a toe flexor dynamometer. Foot arch height was assessed as the distance between the navicular tuberosity of the foot and the floor in the standing position, and foot arch height relative to the foot length was represented by the foot arch index (FAI). For physical performance involving the lower limbs, 50-m sprint, standing broad jump, repeated side step, and rebound jump were measured. RESULTS There were no significant correlations between TFS and FAI and between relative TFS (relative TFS = TFS/body mass) and FAI. Relative TFS was significantly correlated with all physical performance tests. No significant correlations among FAI and physical performances were found, except for rebound jump ability in fifth graders. After multiple regression analyses adjusting for gender and body mass, TFS was the only significant correlating factor for all physical performances involving the lower limbs. CONCLUSIONS This study showed that TFS was associated with enhancement of some measures of lower limb physical performance in children. These results suggest that foot function should be evaluated with both the muscle strength and arch height of the foot in children.

Blood Flow Restriction Exercise in Sprinters and Endurance Runners

PURPOSE We demonstrated that blood flow restriction (BFR) remarkably enhances muscular metabolic stress in resistance exercise, although there is a wide range of individual differences in the responses. It is possible that these differences could be due to training status and muscular physiological characteristics. We investigated intramuscular metabolic responses during low-intensity resistance exercise with BFR between two different types of track athletes. METHODS Twelve age-matched male track athletes (sprinter group, n = 6; endurance runner group, n = 6) were recruited and performed unilateral plantarflexion (30 repetitions per minute). The exercise protocols were as follows: low-intensity exercise at 20% of one-repetition maximum (1RM) (L), high-intensity exercise at 65% 1RM without BFR (1.3 times of systolic blood pressure), L with BFR for 2 min (L-BFR), and prolonged exercise time in L-BFR for 3 min (prolonged BFR). Metabolic stress, defined as phosphocreatine and intramuscular pH decrease, and muscle fiber recruitment were evaluated using P magnetic resonance spectroscopy. RESULTS Endurance runners showed higher peak oxygen uptake and lower muscle strength than sprinters. Phosphocreatine decreases in endurance runners during exercise with BFR protocols were significantly greater than those in sprinters (P < 0.05), although those occurring during L were significantly lower than those in sprinters (P < 0.05). The changes in intramuscular pH and the incidence of fast-twitch fiber recruitment did not show a statistical difference between the two groups. Phosphocreatine decreases in L-BFR were significantly correlated with peak oxygen uptake (P < 0.05). CONCLUSIONS The effects of low-intensity resistance exercise with BFR are greater in endurance runners according to higher aerobic capacity.

Direct and indirect relationships of physical fitness, weight status, and learning duration to academic performance in Japanese schoolchildren

Abstract The purpose of this study was to determine, using structural equation modelling (SEM), the direct and indirect influence of daily behaviours (i.e. exercise/learning durations), weight status, and physical fitness on academic performance among seventh-grade schoolchildren, after controlling for socioeconomic status. We analysed cross-sectional data from 274 schoolchildren (159 males and 115 females; 12–13 years old). Academic performance was assessed using the total grade points in eight academic subjects. Physical fitness was evaluated using the total score of eight physical fitness tests and weight status using body mass index. The daily behaviours and socioeconomic status were assessed by the questionnaire. The SEM showed an adequate fit to the data (χ2 = 0.684, p = .710, RMSEA = .000). Physical fitness and learning durations had direct effects on academic performance (β = .301, p < .001; β = .132, p = .037, respectively) after controlling for confounders. Healthy weight status and exercise habits positively indirectly influenced academic performance via physical fitness. These findings suggest that, independent of socioeconomic status and learning durations, exercise habits and maintaining healthy weight status may indirectly contribute to academic success via better physical fitness in children.

Intramyocellular lipid is increased in the skeletal muscle of patients with dilated cardiomyopathy with lowered exercise capacity

Title Intramyocellular lipid is increased in the skeletal muscle of patients with dilated cardiomyopathy with lowered exercise capacity Author(s) Hirabayashi, Kagami; Kinugawa, Shintaro; Yokota, Takashi; Takada, Shingo; Fukushima, Arata; Suga, Tadashi; Takahashi, Masashige; Ono, Taisuke; Morita, Noriteru; Omokawa, Masashi; Harada, Kuniaki; Manabe, Noriko; Shirato, Hiroki; Matsushima, Shouji; Okita, Koichi; Tsutsui, Hiroyuki Citation International Journal of Cardiology, 176(3), 1110-1112 https://doi.org/10.1016/j.ijcard.2014.07.113 Issue Date 2014-10-20

Modeling relationships of achievement motivation and physical fitness with academic performance in Japanese schoolchildren: Moderation by gender

The aim of this study was to determine, using structural equation modeling, the comprehensive relationships of achievement motivation (self-fulfillment achievement motivation [SFAM] and competitive achievement motivation [CAM]), daily behaviors (exercise habits, screen time, and learning duration), body mass index [BMI], and cardiorespiratory fitness [CRF]) with academic performance among schoolchildren. Three hundred twenty-five schoolchildren (172 males and 153 females; 12-13 years old) were recruited. Academic performance was assessed using the total grade points in 8 academic subjects (GP8); CRF using the 20-m shuttle run; and achievement motivation, daily behaviors, and socioeconomic status using questionnaires. Socioeconomic status was included as a control variable. In males, two cascade associations of achievement motivation to GP8 were detected: (1) SFAM → screen time/learning duration → GP8, and (2) CAM → exercise habit → CRF → GP8 (χ2 = 8.72, p = .19, AGFI = .92). In females, two cascade associations were also detected: (1) SFAM → screen time/learning habit → GP8, and (2) exercise habit → BMI2 → GP8 (χ2 = 6.17, p = .41, AGFI = .93). Our results suggest that greater achievement motivation is associated with academic success via various physiological/behavioral factors, and that these associations differ by gender.

Sapporo Fitness Club Trial (SFCT)

Background The annual health check followed by lifestyle recommendations has long been the standard national strategy to improve cardiovascular disease (CVD) risk factors in Japan. Exercise at fitness clubs, now widely accessible in major cities, has a novel appeal as a strategy with the additive effect of CVD risk reduction. The Sapporo Fitness Club Trial (SFCT) is a randomized controlled trial to compare the efficacy of the national standard alone (control) with the standard plus exercise at a fitness club (intervention) for the reduction of CVD risk factors. Methods The SFCT has recruited and randomized 561 relatively inactive overweight men and women, aged 40-85 years, with elevated levels of 2 or more of the following: systolic blood pressure, fasting blood glucose, and low-density lipoprotein cholesterol. The intervention group was required to exercise at a fitness club 2-4 times per week. At the end of 6 months, risk factors, aerobic capacity, health-related quality of life measures, and adverse effects are to be compared. Conclusion The SFCT is expected to have a major impact in Japan on public health recommendations on exercise for the reduction of lifestyle-related disease. (Circ J 2004; 68: 1199 - 1204)