Acute effects of low-intensity one-legged electrical muscle stimulation on arterial stiffness in experimental and control limbs.

The aim of this study was to examine the acute effects of low-intensity one-legged electrical muscle stimulation (EMS) for skeletal muscle on arterial stiffness in EMS and non-EMS legs. Eighteen healthy subjects received two different protocols (Control (CT) and Experimental (ET) trials) in random order on separate days. EMS was applied to the left lower limb at 4 Hz for 20 min at an intensity corresponding to an elevation in pulse rate of approximately 15 beats/min (10.9 ± 5.1% of heart rate reserve). Before and after the experiment, arterial stiffness parameters in the control right leg (CRL) and control left leg (CLL) in CT and non-EMS leg (NEL) and EMS leg (EL) in ET were assessed by pulse wave velocity (baPWV, faPWV) and cardio-ankle vascular index (CAVI). No significant changes in all parameters were observed in either leg in CT. Conversely, in ET, low-intensity, single-leg EMS significantly reduced CAVI, baPWV, and faPWV in the EL, but not in the NEL. Acute, low-intensity single-leg EMS reduces arterial stiffness only in the EL. These data support our idea that physical movement-related regional factors rather than systematic factors are important for inducing acute reductions in arterial stiffness.

Graded arc beam in light needle microscopy for axially resolved, rapid volumetric imaging without nonlinear processes.

High-speed three-dimensional (3D) imaging is essential for revealing the structure and functions of biological specimens. Confocal laser scanning microscopy has been widely employed for this purpose. However, it requires a time-consuming image-stacking procedure. As a solution, we previously developed light needle microscopy using a Bessel beam with a wavefront-engineered approach [Biomed. Opt. Express13, 1702 (2022)10.1364/BOE.449329]. However, this method applies only to multiphoton excitation microscopy because of the requirement to reduce the sidelobes of the Bessel beam. Here, we introduce a beam that produces a needle spot while eluding the intractable artifacts due to the sidelobes. This beam can be adopted even in one-photon excitation fluorescence 3D imaging. The proposed method can achieve real-time, rapid 3D observation of 200-nm particles in water at a rate of over 50 volumes per second. In addition, fine structures, such as the spines of neurons in fixed mouse brain tissue, can be visualized in 3D from a single raster scan of the needle spot. The proposed method can be applied to various modalities in biological imaging, enabling rapid 3D image acquisition.

Effects of acute cervical stretching on arterial wall elastic properties.

Purpose: Acute (immediate) or regular (mid- or long-term) stretching increases arterial compliance and reduces arterial stiffness. Stretching is widely known to induce arterial functional factor changes, but it is unclear whether stretching alters arterial structural factors. Ultrasound shear wave elastography can quantify the distribution of tissue elastic properties as an index of arterial structural factors. This study thus aimed to examine the effects of acute cervical stretching on arterial wall tissue elastic properties. Methods: Seventeen healthy young adults participated in two different trials for 15 min in random order on separate days: a resting and sitting trial (CON) and a supervised cervical stretching trial (CS). In CS, subjects performed 10 different stretches. At each site, the stretch was held for 30 s followed by a 10-s relaxation period. In CON, subjects rested on a chair for 15 min. Results: After the experiment, carotid arterial compliance, assessed by combined ultrasound imaging and applanation tonometry, was significantly increased in CS, but not in CON. However, there was no significant change in tissue elasticity properties of the arterial wall in either trial, as assessed by ultrasound shear wave elastography. Conclusion: Acute cervical stretching significantly increased carotid artery compliance in young participants, but did not reduce elastic tissue properties (i.e., arterial structural factors) of the carotid artery wall. These results strongly suggest that changes in structural factors have little relation to stretching-induced acute increases in arterial compliance.

Three-minute bench step exercise as a countermeasure for acute mental stress-induced arterial stiffening.

Acute mental stress (MS) induces a transient increase in arterial stiffness. We verified whether a single bout of bench step (BS) exercise for 3 minutes counteracts acute MS-induced arterial stiffening. Fifteen healthy young men (mean age, 21.7 ± 0.3 years) underwent two experimental trials: rest (RE) and exercise (EX) trials. Following a 5-minute MS task, the participants in the RE trial rested on a chair for 3 minutes (from 10 to 13 minutes after task cessation), whereas those in the EX trial performed the BS exercise for the same duration. The heart-brachial pulse wave velocity (PWV) (hbPWV), brachial-ankle PWV (baPWV), heart-ankle PWV (haPWV), and the cardio-ankle vascular index (CAVI) were measured at baseline and at 5 and 30 minutes after the task. In both trials, significant increases in hbPWV, haPWV, and CAVI occurred at 5 minutes after the task; these elevations persisted until 30 minutes after the task in the RE trial, but significantly decreased to baseline levels in the EX trial. baPWV was significantly elevated at 30 minutes after the task in the RE trial, but not in the EX trial. This study reveals that a 3-minute BS exercise offsets acute MS-induced arterial stiffening.

Neighborhood-level socioeconomic factors moderate the association between physical activity and relative age effect: a cross-sectional survey study with Japanese adolescents.

BACKGROUND: Relative age effect is defined as a phenomenon where children born early generally perform better than children born later in the same cohort. Physical activity is an important factor that might be influenced by the relative age effect. Socioeconomic factors (e.g., parent's income, education level) are also associated with the adolescent's physical activity. However, no existing study has examined whether socioeconomic factors moderate the relative age effect on the adolescent's physical activity. This study aims to clarify whether and how birth month and socioeconomic factors relate to organized sports and physical activity among adolescents in Japan. METHODS: We conducted a questionnaire survey targeting 21,491 adolescents who live in a widespread neighborhood. We included 8102 adolescents (4087 males and 4015 females: mean age 13.1 ± 1.4) in the analysis. Based on the participants' birth months, we divided them into four groups (April to June, July to September, October to December, January to March). We asked participants to report their organized sports participation. Using the International Physical Activity Questionnaire for Japanese Early Adolescents, we identified their moderate to vigorous physical activity (MVPA). Neighborhood-level socioeconomic factors (areal deprivation, average annual income, education level) were analyzed based on national surveys, such as the population census. We performed multilevel logistic and linear regression analysis for organized sports participation and MVPA, respectively. Moreover, a simple slope analysis was implemented if the interaction between birth month and socioeconomic factor was significant in the multilevel linear regression analysis. RESULTS: Among males, relatively younger adolescents (adolescents who were born later in the same grade) were less likely to participate in organized sports activites (OR=0.90, 95% CI 0.82-0.97, p<0.05), while both males and females engaged in less MVPA (b=-0.54, b=-0.25, p< 0.01, respectively). We observed an interaction between birth month and socioeconomic factors. Among males in low-income neighborhoods, and females in more deprived neighborhoods, relatively younger adolescents engaged in less MVPA. CONCLUSIONS: Socioeconomic factors moderate the relative age effect on adolescents' physical activity. The relative age effect on adolescents' physical activity might be more likely to appear among adolescents from socioeconomically disadvantaged neighborhoods.

Impact of acute mental stress on ankle blood pressure in young healthy men: a pilot study.

OBJECTIVE: Acute mental stress (MS) increases arm blood pressure (BP); however, it remains unclear whether a stress-induced pressor response is also observed in other vessels. This study aimed to examine the impact of acute MS on ankle BP. Fifty-six young, healthy men aged 19-24 years were divided into the MS (n = 29) and control (CON) (n = 27) groups; each group performed 5-min MS (mental arithmetic) or CON tasks. Systolic and diastolic BPs (SBP and DBP, respectively) of both the brachial and posterior tibial arteries were simultaneously measured at the baseline and 5 and 30 min after the task. RESULTS: In the MS group, brachial BP measures significantly increased (P < 0.05) until 30 min after the task; ankle BP measures were also significantly (P < 0.05) elevated during this time. In the CON group, no significant changes were found in brachial BP measures or ankle SBP, whereas a significant increase (P < 0.05) in ankle DBP was observed 30 min after the task. Our findings indicate that both brachial and ankle BP exhibit a sustained elevation after acute MS, suggesting a systemic pressor response by stress exposure. The measurement of ankle BP in addition to arm BP may be important to assess the stress response. TRIAL REGISTRATION: UMIN Clinical Trials Registry UMIN000047796 Registered on: 20th May 2022.

The effectiveness of bench step exercise for ameliorating acute mental stress-induced arterial stiffening.

PURPOSE: This study aimed to evaluate the effectiveness of bench step (BS) exercise for ameliorating arterial stiffening caused by acute mental stress (MS). METHODS: Fifteen young healthy men participated in two randomized trials: rest (RE) and exercise (EX) trials. Following a 5-min MS task (first task), the RE trial participants rested on a chair for 10 min (from 10 to 20 min after task cessation); the EX trial participants performed BS exercise for the same duration. At 40 min after the first task, the participants performed the same task (second task) again. Heart-brachial pulse wave velocity (PWV) (hbPWV), brachial-ankle PWV (baPWV), heart-ankle PWV (haPWV), and the cardio-ankle vascular index (CAVI) were measured simultaneously at 5, 30, and 50 min after the first task. RESULTS: Both trials caused significant elevations in hbPWV, haPWV, and CAVI at 5 min after the first task; these changes persisted until 30 min after the task in the RE trial, while they were abolished in the EX trial. baPWV significantly increased at 30 min after the task in the RE trial, but not in the EX trial. After the second task (from 30 to 50 min after the first task), none of the parameters significantly increased in the RE trial, although the values remained above baseline levels. In the EX trial, hbPWV, haPWV, and CAVI showed significant elevations. CONCLUSION: Our findings suggest that a 10-min BS exercise after acute MS can counteract stress-induced arterial stiffening, but has only a limited effect against subsequent acute MS.

Association of Neighborhood Food Environment and Physical Activity Environment With Obesity: A Large-Scale Cross-Sectional Study of Fifth- to Ninth-Grade Children in Japan.

Objective: This study examined the relationship between neighborhood food and physical activity environment, and obesity among elementary and junior high school students in Japan. Methods: The participants were fifth- to ninth-grade children (n=7277), who were attending municipal schools in Japan. Percent overweight (POW) was calculated using their age, gender, height, and weight, which were collected through a questionnaire. A POW of < 20% was considered non-obese, while ≥ 20% was considered obese. Furthermore, using a geographic information system, we investigated the density of convenience stores, fast-food stores, casual restaurants, supermarkets and department stores, parks, sports facilities, stations, and intersections in the school district. Additionally, from the census, we obtained information regarding the population density of the municipality where the participants' schools were located. Multiple logistic regression analysis was used to examine the relationship between obesity and food environment (the food environment model), between obesity and physical activity environment (the physical activity environment model), and among obesity, food, and physical activity environment (the food and physical activity environment model). Results: In the food environment model and the food and physical activity environment model, the density of convenience stores showed a significant positive association. In the physical activity environment model, the density of stations showed a significant negative association. Conclusion: This study's findings can contribute to the development of appropriate community interventions for improving children's health in Japan and similar areas.

Acute mental stress-caused arterial stiffening can be counteracted by brief aerobic exercise.

PURPOSE: Acute mental stress (MS) causes an elevation in pulse wave velocity (PWV), an index of arterial stiffness. In contrast, aerobic exercise acutely decreases arterial stiffness, even in the short term. The present study aimed to examine whether acute MS-caused arterial stiffening can be counteracted by brief aerobic exercise. METHODS: Thirteen young healthy men (mean age, 20 ± 1 years) participated in two randomized experimental visits where they were subjected to acute MS followed by seated rest (RE) or cycling exercise (EX) trials. Following a 5-min MS task, the participants in the RE trial rested on a chair for 10 min (from 10 to 20 min after the cessation of the task), whereas those in the EX trial cycled at 35% of heart rate reserve for the same duration. Heart-brachial PWV (hbPWV), brachial-ankle PWV (baPWV), heart-ankle PWV (haPWV), and the cardio-ankle vascular index (CAVI) were simultaneously measured at baseline and 5, 30, and 45 min after the task. RESULTS: Both trials caused significant elevations (P < 0.05) in hbPWV, haPWV, and CAVI at 5 min after the task; subsequently, this persisted until 45 min after the task in the RE trial, whereas the elevations in the EX trial were eliminated. In the RE trial, baPWV significantly increased (P < 0.05) at 30 and 45 min after the task, whereas such an increase was not observed in the EX trial. CONCLUSION: The findings of the present study reveal that brief aerobic exercise counteracts arterial stiffening caused by acute MS.

Impact of acute mental stress on segmental arterial stiffness.

PURPOSE: It has been reported that acute brief episodes of mental stress (MS) result in a prolonged increase in carotid-femoral pulse wave velocity (cfPWV), an index of aortic stiffness. However, whether acute MS also impacts arterial stiffness in other segments is unclear. The present study aimed to examine the impact of acute MS on segmental arterial stiffness. METHODS: In the main experiment, 17 young male subjects (mean age, 20.1 ± 0.7 years) performed a 5-min MS and control (CON) task in a random order. Pulse wave velocity (PWV) from the heart to the brachium (hbPWV) and the ankle (haPWV), PWV between the brachial artery and the ankle (baPWV), and the cardio-ankle vascular index (CAVI) were simultaneously measured at baseline and 5, 15, and 30 min after the task. RESULTS: Compared to baseline values, hbPWV, baPWV, haPWV, and CAVI significantly increased until 30 min after the MS task, whereas these variables did not significantly change following the CON task. At 5 and 30 min after the MS task, percentage changes from baseline were significantly higher in hbPWV (+ 5.2 ± 4.4 and 6.6 ± 4.9%) than in baPWV (+ 2.2 ± 2.1 and 2.2 ± 2.0%) or haPWV (+ 3.6 ± 2.6 and 4.3 ± 2.9%) and were also significantly lower in baPWV than in haPWV. CONCLUSION: These findings suggest that acute MS elicits an increase in arterial stiffness in various segments and this arterial stiffening is not uniform among the segments.

Onset of Accelerated Muscle Deoxygenation During the 20-m Shuttle Run Test in Boys.

PURPOSE: This study aimed to compare the relative exercise intensity at which the onset of accelerated muscle deoxygenation occurs during the 20-m shuttle run test (20mSRT) between boys and men and to examine whether the timing of the onset of acceleration appearance is related to 20mSRT performance in boys. METHODS: Twenty-four boys performed the 20mSRT, during which concentration changes in oxygenated and deoxygenated hemoglobin and myoglobin (ΔOxy-Hb and ΔDeoxy-Hb, respectively) in the m. vastus lateralis were monitored using a portable near-infrared spectroscopy device. The boys' data were compared with those of 29 men in a previous study. RESULTS: An onset of accelerated decrease in Δ[Oxy-Hb - Deoxy-Hb] was found in 11 of the 24 boys (45.8%) and 20 of the 29 men (69.0%) and was found at a higher relative exercise intensity in the boys than in the men. The number of laps at which the onset of acceleration occurred correlated with total laps in the boys (r = .87). CONCLUSIONS: These findings demonstrate that the onset of accelerated muscle deoxygenation during the 20mSRT occurs at a higher relative exercise intensity in boys than in men. Our findings also show that the timing of the onset of acceleration appearance is associated with 20mSRT performance in boys.

Accelerated point of muscle deoxygenation during the 20-m shuttle run test.

This study examined whether the point of accelerated deoxygenation of active muscle occurs during the 20-m shuttle run test (20mSRT) and, if so, whether it is associated with exercise performance in the test. Twenty-nine male subjects performed the 20mSRT, and concentration changes in oxyhaemoglobin (ΔOxy-Hb) and deoxyhaemoglobin (ΔDeoxy-Hb) in the m. vastus lateralis were measured using a portable near-infrared spectroscopy device. The difference between the relative concentration changes in ΔOxy-Hb and ΔDeoxy-Hb (Δ[Oxy-Hb - Deoxy-Hb]) was regarded as the muscle oxygenation index. Group-averaged Δ[Oxy-Hb - Deoxy-Hb] showed progressive decrease during the test. However, among the individuals, we found an accelerated point of decrease in Δ[Oxy-Hb - Deoxy-Hb] in 20 subjects, which revealed that the laps at the accelerated point correlated with the total laps (r = 0·78). These results demonstrate that the accelerated deoxygenation of active muscle occurs during the 20mSRT, but not in all cases. Our findings also indicate that if the accelerated point of muscle deoxygenation occurs, the timing of its appearance is related to 20mSRT performance.

Does voluntary hypoventilation during exercise impact EMG activity?

It has been reported that exercise under hypoxic conditions induces reduced muscle oxygenation, which could be related to enhanced activity on electromyography (EMG). Although it has been demonstrated that exercise under conditions of voluntary hypoventilation (VH) evokes muscle deoxygenation, it is unclear whether VH during exercise impacts EMG. Seven men performed bicycle exercise for 5 min at 65 % of peak oxygen uptake with normal breathing (NB) and VH. Muscle oxygenation; concentration changes in oxyhemoglobin (Oxy-Hb), deoxyhemoglobin (Deoxy-Hb) and total hemoglobin (Total-Hb); and surface EMG in the vastus lateralis muscle were simultaneously measured. In the VH condition, Oxy-Hb was significantly lower and Deoxy-Hb was significantly higher compared to those in the NB condition (P < 0.05 for both), whereas there was no significant difference in Total-Hb between the two conditions. We observed significantly higher values (P < 0.05) on integrated EMG during exercise under VH conditions compared to those under NB conditions. This study suggests that VH during exercise augments EMG activity.