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There is no evidence of the effect of exercise training on human brown-like adipose tissue vascular density (BAT-d). Here, we report whether whole-body strength training (ST) in a cold environment increased BAT-d. The participants were 18 men aged 20–31 years. They were randomly assigned to two groups: one that performed ST twice a week at 75% intensity of one-repetition maximum for 10 weeks during winter (EX; n = 9) and a control group that did not perform ST (CT; n = 9). The total hemoglobin concentration in the supraclavicular region determined by time-resolved near-infrared spectroscopy was used as a parameter of BAT-d. ST volume (Tvol) was defined as the mean of the weight × repetition × sets of seven training movements. The number of occasions where the room temperature was lower than the median (NRcold) was counted as an index of potential cold exposure during ST. There was no significant between-group difference in BAT-d. Multiple regression analysis using body mass index, body fat percentage, NRcold, and Tvol as independent variables revealed that NRcold and Tvol were determined as predictive of changes in BAT-d. An appropriate combination of ST with cold environments could be an effective strategy for modulating BAT.

Background/objectives The thermogenic function of brown adipose tissue (BAT) is generally activated in winter and tightly regulated through various metabolic processes. However, the mechanisms mediating these changes have not been elucidated in humans. Here, we investigated the relationships between BAT density (BAT-d) and lipid metabolites in plasma from men and women in the winter and summer. Subjects/methods In total, 92 plasma samples were obtained from 23 men and 23 women, aged 21–55 years, on two different occasions (summer and winter). Lipid metabolites were comprehensively quantified using liquid chromatography-time-of-flight-mass spectrometry. BAT-d was evaluated by measuring total hemoglobin concentrations in the supraclavicular region using near-infrared time-resolved spectroscopy. Anthropometric parameters, such as the percentage of whole body fat and visceral fat area (VFA), were evaluated. Factors influencing BAT-d were investigated by univariate and multivariate regression analyses. Results A variety of metabolite peaks, such as glycerophospholipids (168 peaks), steroids and derivatives (78 peaks), fatty acyls (62 peaks), and glycerolipids (31 peaks), were detected. Univariate regression analysis, corrected by false discovery rate to yield Q values, revealed significant correlations in BAT-d and phosphatidylethanolamine (PE(46:2), r = 0.62, Q = 4.9 × 10−2) in the summer, androgens (r = 0.75, Q = 7.0 × 10−3) in the winter, and diacylglycerol (DG(36:1), r = −0.68, Q = 4.9 × 10−2) in the summer in men, but not in women. Multivariate regression analysis in the winter revealed a significant correlation between BAT-d and plasma androgens (P = 5.3 × 10−5) in men and between BAT-d and VFA (P = 2.2 × 10−3) in women. Conclusions Certain lipids in plasma showed unique correlations with BAT-d depending on sex and season. BAT-d showed a specific correlation with plasma androgens in men in the winter.

The primary symptom in patients with chronic heart failure (CHF) is exercise intolerance. Previous studies have reported that reduced exercise tolerance in CHF can be explained not only by cardiac output (a central factor) but also by reduced skeletal muscle aerobic capacity (a peripheral factor). Although exercise training in CHF improves exercise tolerance, few studies have evaluated the effects of exercise training on each specific central and peripheral factor in CHF. The aim of this study was to investigate the central and peripheral aerobic functions in CHF and the effects of exercise training in CHF on cardiac output and skeletal muscle deoxygenation during exercise. We assessed peak oxygen uptake (VO

Previous studies have reported that the reduced scattering coefficient (μ

Brown adipose tissue (BAT) is negatively correlates with adiposity in adult humans. Near-infrared time-resolved spectroscopy has been used to noninvasively measure the density of BAT (BAT-d). We examined the relationship between body adiposity and total hemoglobin concentration in the supraclavicular region ([total-Hb]sup), that is a parameter for BAT-d, in healthy children (113 boys and 127 girls, aged 1 month to 5 years). Age and [total-Hb]sup were significant predictors of the Kaup index and subcutaneous adipose tissue thickness. BAT-d, determined by [total-Hb]sup, was negatively associated with body adiposity in infants, which is in line with the result found in adults.

The aim of this study was to investigate the relationship between brown adipose tissue density (BAT-d) and muscle strength, one of the major parameters relating to physical fitness. The total hemoglobin concentration ([Total-Hb]) , an index of BAT-d in the supraclavicular region using near-infrared time-resolved spectroscopy, handgrip strength, and leg-extension strength were measured in winter in healthy adults (n = 27). BAT-d was not correlated with handgrip strength (r = 0.18, p = 0.37), but with 1-RM leg extension (r = 0.41, p < 0.05). A higher leg muscle strength was associated with a higher BAT-d.

The primary symptom in patients with chronic heart failure (CHF) is exercise intolerance. Previous studies have reported that reduced exercise tolerance in CHF can be explained not only by cardiac output (a central factor) but also by reduced skeletal muscle aerobic capacity (a peripheral factor). Although exercise training in CHF improves exercise tolerance, few studies have evaluated the effects of exercise training on each specific central and peripheral factor in CHF. The aim of this study was to investigate the central and peripheral aerobic functions in CHF and the effects of exercise training in CHF on cardiac output and skeletal muscle deoxygenation during exercise. We assessed peak oxygen uptake (VO2) during cardiopulmonary exercise testing, peak cardiac output (CO) using noninvasive hemodynamic monitoring, and muscle oxygen saturation (SmO2) using near-infrared spectroscopy (NIRS). Patients with CHF were trained for 12 weeks and performed ramp cycling exercise until exhaustion before and after the exercise training. Peak VO2, peak CO, and SmO2 changes from rest to peak exercise (ΔSmO2) were significantly lower in CHF than those in healthy subjects. As a result of exercise training, peak oxygen uptake in patients with CHF was improved and positively associated with change in ΔSmO2. In contrast, there was no change in peak cardiac output. The results of this study indicate that both cardiac and skeletal muscle functions in patients with CHF were lower than those in healthy subjects. Further, the results suggest that the improvement of exercise capacity in patients with CHF by exercise training was related to the improved utilization of oxygen (a peripheral factor) in skeletal muscle.

Previous studies have reported that the reduced scattering coefficient (μs′) in the vastus lateralis changes during ramp-incremental exercise due to blood volume changes or accumulation of metabolic by-products. We aimed to clarify the influences of deoxygenation and blood volume changes during exercise on μs′ dynamics in subjects with various aerobic capacities. Twenty-three healthy young men participated in this study. All subjects performed a ramp-incremental cycling exercise until exhaustion and were divided into two groups: lower (Low: n = 12; peak pulmonary oxygen uptake per kg of fat-free mass (VO2peak), 54.2 ± 5.3 mL/kg/min) and higher aerobic capacity group (High: n = 11; VO2peak, 69.7 ± 5.2 mL/kg/min) by median of VO2peak. Deoxygenated hemoglobin and myoglobin concentrations (deoxy[Hb + Mb]) and total [Hb + Mb] (total[Hb + Mb]) in the vastus lateralis were monitored during the exercise by three-wavelength (760, 800, and 830 nm) time-resolved NIRS. Similarly, μs′ at each wavelength was continuously monitored. With increasing exercise intensity, deoxy[Hb + Mb] and total[Hb + Mb] significantly increased in both groups, and the average values of the peak amplitudes of deoxy[Hb + Mb] and total[Hb + Mb] during exercise showed a 106.4% increase and a 17.9% increase from the start of the exercise, respectively. Furthermore, the peak amplitude of total[Hb + Mb] was significantly greater in High. Conversely, there were no changes in μs′ at any wavelength during exercise and no differences between two groups, suggesting that the great deoxygenation and blood volume changes during incremental exercise have little effect on μs′ dynamics.

PURPOSE Near-infrared spectroscopy (NIRS), performed with a commonly available noninvasive tissue oxygenation monitoring device, is based on the modified Beer-Lambert law (MBLL). Although NIRS based on MBLL (NIRSMBLL) assumes that the optical path length (PL) is constant, the effects of changes in PL during exercise on muscle oxygenation calculated by MBLL are still incompletely understood. Thus, the purposes of this study were to examine the changes in optical properties during ramp incremental exercise and to compare muscle oxygen dynamics measured by time-resolved NIRS with those calculated based on MBLL. METHODS Twenty-two healthy young men performed ramp incremental cycling exercise until exhaustion. Optical properties (reduced scattering coefficient and PL) and absolute oxygenated, deoxygenated, and total hemoglobin and myoglobin concentrations (oxy[Hb + Mb], deoxy[Hb + Mb], and total[Hb + Mb], respectively) at the vastus lateralis were continuously monitored by a three-wavelength (763, 801, and 836) time-resolved NIRS device. The values of oxy-, deoxy-, and total[Hb + Mb] were then recalculated by assuming constant PL. RESULTS PL at all wavelengths statistically significantly shortened during exercise. In particular, PL at 763 nm was greatly shortened, and the average changes during exercise were a 9.8% ± 3.1% reduction. In addition, significant differences in the kinetics of oxy-, deoxy-, and total[Hb + Mb] between directly measuring PL and assuming constant PL were found. The average changes in measured PL and assuming constant PL-deoxy[Hb + Mb] were increases of 28.8 ± 16.0 μM and increases of 16.4 ± 9.3 μM, respectively. CONCLUSION Assuming constant PL in NIRSMBLL significantly underestimated actual muscle oxy/deoxygenation as compared with measurements obtained by real-time PL determination. The percent degree of the underestimated oxy/deoxygenation was greater than the percent degree of the changes in PL.

Brown adipose tissue (BAT) plays a role in adaptive thermogenesis in response to cold environments and dietary intake via sympathetic nervous system (SNS) activation. It is unclear whether physical activity increases BAT density (BAT-d). Two-hundred ninety-eight participants (age: 41.2 ± 12.1 (mean ± standard deviation), height: 163.6 ± 8.3 cm, weight: 60.2 ± 11.0 kg, body mass index (BMI): 22.4 ± 3.0 kg/m2, body fat percentage: 25.4 ± 7.5%) without smoking habits were categorized based on their physical activity levels (a group performing physical activities including walking and moderate physical activity (WM) and a group performing WM + vigorous-intensity physical activities (VWM)). We measured the total hemoglobin concentration ([Total-Hb]) in the supraclavicular region, an index of BAT-d, and anthropometric parameters. [Total-Hb] was significantly higher in VWM than WM for all participant groups presumably owing to SNS activation during vigorous-intensity physical activities, and unrelated to the amount of total physical activity levels. Furthermore, multiple regression analysis revealed that BAT-d was related to visceral fat area and VWM in men and related to body fat percentage in women. We conclude that vigorous-intensity physical activities are associated with high BAT-d in humans, especially in men.

Mitochondrial oxidative phosphorylation, which modulates resynthesis of PCr, depends in part on the availability of O2 for the mitochondria in working muscle. Particularly during intense exercise, the induced lower O2 availability due to hypoxic condition by inadequate blood flow affects mitochondrial oxidative phosphorylation. However, there are few studies which have reported the relationship between mitochondrial stimuli and oxygen diffusion rate from capillary to mitochondria in skeletal muscle (muscle rDO2) during varying-workload exercise including under severe acidosis conditions in humans. The purpose of this study was to investigate the relationship between muscle PCr, rDO2, and muscle deoxygenation in humans during incremental dynamic exercise. Twelve healthy, nonsmoking male subjects participated in this study. The subjects performed incremental dynamic handgrip exercise until exhaustion. Muscle PCr during exercise was evaluated using 31-phosphorus magnetic resonance spectroscopy. Muscle deoxygenation level was monitored using near-infrared spectroscopy, and muscle rDO2 was determined by the rate of muscle deoxygenation during temporary arterial occlusion immediately after the end of each exercise stage. Muscle PCr level subsequently decreased with higher workloads, and muscle rDO2 above 10%MVC significantly increased from the resting, and was constant with higher workloads. Muscle deoxygenation level was also significantly greater above 10%MVC, and gradually increased with higher workloads. These results suggest that muscle rDO2 is limited at higher workloads, although mitochondrial stimuli are increased. The constant muscle rDO2 with higher workloads may be caused by reduced O2 gradient from capillary to mitochondria.

Brown/beige adipose tissue (BAT) is expected to contribute to protecting lifestyle-related diseases. The purpose of this study was to examine if near-infrared time-resolved spectroscopy (NIRTRS) is capable of distinguishing BAT from muscle and white adipose tissue (WAT). We analyzed the optical characteristics of tissues in the supraclavicular region, where BAT deposits can be located, and deltoid and abdominal regions in 36 participants (16 men and 20 women) who were apparently healthy individuals, with a median age of 44.5 years, in winter and summer. They also had a median body fat percentage of 28.3% and a deltoid and abdominal adipose tissue thickness of 0.85 cm and 1.71 cm, respectively. The total hemoglobin concentration [total-Hb] and the reduced scattering coefficient (μs′) were determined using nearinfrared time-resolved spectroscopy (NIRTRS) with a 3 cm optode separation for supraclavicular and deltoid regions and a 2 cm optode separation for abdominal region. The results regarding data collected in winter were the following: deltoid (μs' = 9.6 [9.1, 10.4] cm-1 , [total-Hb] = 114.9 [107.0, 127.7] μM); abdominal (μs' = 9.0 [7.9, 10.1] cm-1 , [total-Hb] = 11.2 [8.0, 16.0] μM); and supraclavicular (μs' = 7.9 [7.2, 8.7] cm-1 , [total-Hb] = 60.7 [48.9, 74.7] μM)) in winter. Some data are overlapped between groups of muscle and BAT. These results indicated that [total-Hb] and μs′ show region-specific characteristics. We conclude that using [total-Hb] - μs′ relationship determined by NIRTRS is a useful strategy to distinguish BAT from other tissues in a simple, rapid, and non-invasive manner.

Near-infrared time-resolved spectroscopy (NIR

Near-infrared time-resolved spectroscopy (NIRTRS) can quantitatively evaluate mean optical path length (MPL). Since an increase in optical absorbers in the NIR region (e.g. an increase in deoxygenated hemoglobin during exercise) would shorten the MPL, the NIRS measurement area may vary depending on physical and physiological characteristics of the measurement region and/or the exercise intensity. The aim of this study was to examine the changes in MPL measured by NIRTRS during ramp cycling exercise between fat layer thickness-matched subjects with different aerobic capacities. Healthy control (CON, n = 8) and endurance-trained males (TR, n = 8) performed ramp cycling exercise until exhaustion. Deoxygenated hemoglobin concentration (Deoxy-Hb), total hemoglobin concentration (Total-Hb) and oxygenated hemoglobin concentration (Oxy-Hb) were evaluated by a three-wavelength NIRTRS system. MPL in each wavelength (MPL760, MPL800 and MPL830) was monitored continuously. With increasing exercise intensity, Total- and Deoxy-Hb significantly increased and Oxy-Hb decreased in both groups. Total- and Oxy-Hb during exercise were significantly higher in TR than CON (P < 0.05, P < 0.01, respectively). Furthermore, Deoxy-Hb also tended to be higher in TR than CON (P = 0.07). In addition, MPL at all wavelengths significantly shortened with an increase in exercise intensity, with no differences between CON and TR. In particular, MPL760 at peak exercise shortened more than 10% compared to the start of exercise in both groups, even though MPL830 decreased only a few per cent. These findings suggest that the NIRS measurement area may be reduced during ramp cycling exercise due to shortened MPL. Additionally, the changes in MPL may be especially greater at 760 nm than at the other wavelengths due to greater changes in Deoxy-Hb during exercise. Furthermore, this study indicates that the measurements of muscle deoxygenation using continuous-wave NIRS can be less accurate since they are significantly affected by changes in the optical path length.

High whole-body and visceral adiposity are risk factors that can cause metabolic diseases. We hypothesized that the total hemoglobin concentration (total-Hb) in abdominal subcutaneous adipose tissue (SATab), an indicator of white adipose tissue (WAT) vascularity, correlates negatively with risk factors for developing metabolic diseases, such as whole-body and visceral adiposity. We tested the optical characteristics of abdominal tissue in 140 participants (45 men and 95 women) who were apparently healthy individuals with a median age of 39 years. They also had a median body fat percentage of 25.4%, a visceral fat area of 50.4 cm2, and a SATab thickness of 1.05 cm. These tests were conducted using near-infrared time-resolved spectroscopy (NIRTRS) with a 2-cm optode separation. To distinguish the segments of SATab (SegSAT) and the mixture of muscle and SATab (SegSAT+Mus), the threshold was analyzed using the slopes of (total-Hb) against the thickness of SATab using the least-squares mean method. According to the results from the logistic regression analysis, the percentage of body fat and visceral fat area remained significant predictors of the (total-Hb) (p = 0.005 and p = 0.043, respectively) in the data for SegSAT (no influence from the SATab thickness). We conclude that simple, rapid, and noninvasive NIRTRS-determined (total-Hb) in WAT could be a useful parameter for evaluating risk factors for metabolic diseases.

Capsinoids are some of the most promising ingredients to increase energy expenditure (EE) due to brown adipose tissue (BAT) activation. However, there is limited information regarding the effect of prolonged capsinoid ingestion (CI) on BAT activity and resting EE (REE) in healthy, middle-aged, normal to overweight subjects (Subhealthy) with distinct BAT characteristics. We examined the changes in BAT density (BAT-d), using near-infrared time-resolved spectroscopy, and REE/kg induced by daily CI. Forty Subhealthy [age, 43.8 (mean) years, BMI, 25.4 kg/m2] received either capsinoid (9 mg/day) or a placebo daily for 6 weeks in a double-blind design. Total hemoglobin concentration in the supraclavicular region ([total-Hb]sup), an indicator of BAT-d, and REE/kg were measured. The changes in post-intervention [total-Hb]sup were greater in the capsinoid group (CA-G) than in the placebo group (PL-G) [5.8 &micro, M (+12.4%) versus 1.0 &micro, M (+2.1%), p = 0.017]. There was a significant relationship between BAT-d and REE/kg, however, post-supplementation REE/kg was not significantly different between the two groups (p = 0.228). In the overweight subgroup, changes in REE/kg were greater in the CA-G than in the PL-G [0.6 cal/kg/min (+4.3%) versus &minus, 0.3 cal/kg/min (&minus, 2.1%), p = 0.021]. CI enhanced [total-Hb]sup, a reflection of BAT-d, showing a good correlation with REE in Subhealthy.

Fat layer thickness (FLT) affects near infrared spectroscopy (NIRS) measurement. The aim of this study was to determine an indicator of muscle function with less influence of FLT, even without normalization, by comparing muscle O

Background: Near-infrared time-resolved spectroscopy is a non-invasive method that facilitates analysis of human brown adipose tissue (BAT) density. We measured BAT density in middle-aged patients who had type 2 diabetes by this method and examined the relationship using clinical parameters. Methods: We studied 33 Japanese middle-aged diabetic patients (30 male and 3 female, age 53.8±10.1 years, BMI 25.4±4.5, and HbA1c 7.2±1.1%). Tissue hemoglobin concentration (tHb) of the supraclavicular region was measured using near-infrared time-resolved spectroscopy, and normalized by subcutaneous fat thickness at the measurement sites. Results: The average tHb concentration was 51.1±17.7 μM and lower than 77.8 μM—the value equivalent to the detection threshold of BAT by standard FDG-PET in young adults. Univariate regression analysis showed that the tHb of the supraclavicular region was inversely correlated with BMI (r = −0.55, p=0.0009), but the tHb of the deltoid region was not (r = 0.04, p = 0.31). Other parameters showing significant correlations with BAT mass included systolic blood pressure (r = −0.47, p = 0.01) and insulin treatment (r=0.45, p=0.01). Multivariate regression analysis suggested that BMI (β=−0.42, p=0.005), systolic blood pressure (β=−0.29, p=0.042), and insulin treatment (β=0.34, p=0.015) independently account for BAT density. Conclusion: Our findings suggest that BAT density in middle-aged diabetic patients may relate to obesity more closely than previously thought. Disclosure H. Waki: Research Support; Self; MSD K.K., Novartis Pharma K.K., Boehringer Ingelheim Pharmaceuticals, Inc., Sanofi K.K., Ono Pharmaceutical Co., Ltd., Kyowa Hakko Kirin Co., Ltd., Takeda PHarmaceutical Co., Ltd.. N. Watanabe: None. S. Fuse: None. Y. Kurosawa: None. T. Yamauchi: Research Support; Self; Novo Nordisk Inc., Daiichi Sankyo Company, Limited, Sanofi, Takeda, Tanabe-Mitsubishi. R. Kime: None. T. Hamaoka: None. T. Kadowaki: Consultant; Self; Novo Nordisk A/S, AstraZeneca, Merck Sharp & Dohme Corp.. Research Support; Self; Kissei Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Sanofi, Kyowa Hakko Kirin Co., Ltd., Novo Nordisk A/S, Astellas Pharma, Daiichi Sankyo Company, Limited, Takeda, Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Merck Sharp & Dohme Corp., Nippon Boehringer Ingelheim Co. Ltd.. Speaker's Bureau; Self; Astellas Pharma, AstraZeneca, Merck Sharp & Dohme Corp., Ono Pharmaceutical Co., Ltd., Takeda, Eli Lilly and Company, Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk A/S.

F18-fluorodeoxyglucose (FDG)–positron emission tomography (PET) along with computed tomography (CT) is a standard method for assessing brown adipose tissue (BAT) activity. We tested the usefulness of near-infrared time-resolved spectroscopy (NIRTRS) as a simple and noninvasive method for evaluating BAT density (BAT-d) by examining the effects of some factors known to influence BAT activity. The total hemoglobin concentration as a parameter of BAT-d was evaluated using NIRTRS in the supraclavicular region in 413 Japanese individuals. The associations were analyzed between BAT-d and sex, age, the percentages of body fat (%BF), visceral fat (VF), and the seasonal ambient temperature (AmT) fluctuations. Age was associated with decreased BAT-d (P

Fat layer thickness (FLT) affects near infrared spectroscopy (NIRS) measurement. The aim of this study was to determine an indicator of muscle function with less influence of FLT, even without normalization, by comparing muscle O2 dynamics during exercise in subjects with similar physical characteristics except for FLT. Healthy male subjects with thick FLT (n = 5, FLT: 5.3 ± 0.4 mm) and those with thin FLT (n = 6, FLT: 3.5 ± 0.5 mm) participated in this study. All subjects performed constant work cycling exercise (CWE) at moderate intensity for 6 min. Oxygenated hemoglobin concentration, deoxygenated hemoglobin concentration and total hemoglobin concentration were monitored by using time resolved NIRS (NIRTRS). VO2peak was not significantly different between THICK and THIN (THICK: 54.0 ± 1.8, THIN: 50.0 ± 6.2 mL/kg/min). Changes in all NIRTRS variables at the onset of CWE were significantly larger in THIN than THICK, and the changes in each variable were significantly correlated to FLT. In contrast, there were no relationships between changes in NIRTRS variables during CWE and FLT. These results suggest that muscle deoxygenation at the onset of exercise, which is used as muscle O2 extraction, can be strongly influenced by FLT. In contrast, muscle oxygenation during CWE, which is used as exercise-induced functional hyperemia, may not be influenced by FLT.

This study quantitatively analyzed the effects of 3 h of constant sitting on skeletal muscle oxygenation in the lower extremities, using near-infrared time-resolved spectroscopy (NIRTRS). The effects of compression stockings were also evaluated. Eleven healthy men (age, 30.0 &plusmn, 6.7 years) maintained their knee joints at 90&deg, flexion during 3 h of constant sitting and wore a compression stocking on either the right or left leg. The side the stocking was worn was chosen randomly. Subsequently, leg circumference and extracellular water were measured. After 3 h of sitting, both factors increased significantly in uncompressed limbs. Furthermore, intracellular water and muscle oxygenation had significantly decreased. In contrast, extracellular water had not increased in the limbs wearing compression stockings. Furthermore, the increased circumference of compressed limbs was significantly smaller than that of uncompressed limbs. Decreases in oxygenated hemoglobin and total hemoglobin were significantly smaller in compressed limbs than in uncompressed limbs (oxy-Hb, p = 0.021, total-Hb, p = 0.013). Three hours of sitting resulted in decreased intracellular water and increased extracellular water in the lower extremities, leading to reduced blood volume and oxygenation levels in skeletal muscle. Compression stockings successfully suppressed these negative effects.

The purpose of this study was to elucidate the time course of muscle deoxygenation and its heterogeneity changes through endurance training. Nine healthy untrained male participated in this study. The subjects performed a ramp incremental cycle exercise protocol to estimate VO2peak and muscle tissue oxygen saturation (SmO2) distribution in the VL muscle before and after 3 (3 wk-T) and 6 weeks of endurance training (6 wk-T). The probe of multi-channel near infrared spatially resolved spectroscopy was attached to the left vastus lateralis muscle along the direction of the long axis. The subjects performed cycle exercise at 60 % of VO2peak for 30 min/day, 3 days/week as the endurance training. After the training, VO2peak at 3 wk-T and 6 wk-T were significantly increased compared to pre-training (Pre-T) and VO2peak at 6 wk-T was significantly increased compared to 3 wk-T. Mean SmO2 within measurement sites at VO2peak was significantly decreased after 3 wk-T and 6 wk-T compared to Pre-T, but mean SmO2 was not significantly different between 3 wk-T and 6 wk-T. Conversely, the heterogeneity of the SmO2 during exercise was not significantly changed through endurance training. A significantly negative correlation was found between ΔVO2 and ΔSmO2 after the first 3 weeks of endurance training. In contrast, no correlation was found betweenΔVO2 and ΔSmO2 after the last 3 weeks of endurance training. These results suggest that the enhanced muscle O2 availability may be one of the primary factors in increasing VO2peak after the first 3 weeks of endurance training.

An increase in the incidence rate of cardiovascular disease is attributed to high daily sitting time, while a drop in risk of cardiovascular disease comes from a decrease in daily sitting time, rather than an increase in physical activity levels. Although short-duration passive exercise increases energy expenditure and blood flow, few studies have reported on the responses of cardiorespiratory dynamics to long-duration passive exercise. The purpose of this study was to consider the effect of long-duration passive exercise for 20 min on cardiorespiratory and muscle oxygen dynamics. Eight healthy men continuously performed passive exercise using a cycle ergometer for 20 min at 50 rpm. Changes in oxygen uptake, cardiac output and muscle oxygenation were measured during passive cycling exercise. The oxygen uptake at 1 min after the start of passive exercise was significantly increased, compared to resting level, but subsequently returned to the same as resting level. Cardiac output showed no change during passive cycling exercise. Tissue oxygen saturation increased after the start of passive exercise and subsequently maintained steady state. These results suggest that the effect of increases in energy expenditure was not maintained by passive exercise for 20 min. In addition, it is likely that passive cycling exercise for 20 min has an effect on peripheral circulation, although the exercise seems to have no effect on central circulation.

The purpose of this study was to elucidate the time course of muscle deoxygenation and its heterogeneity changes through endurance training. Nine healthy untrained male participated in this study. The subjects performed a ramp incremental cycle exercise protocol to estimate VO2peak and muscle tissue oxygen saturation (SmO2) distribution in the VL muscle before and after 3 (3 wk-T) and 6 weeks of endurance training (6 wk-T). The probe of multi-channel near infrared spatially resolved spectroscopy was attached to the left vastus lateralis muscle along the direction of the long axis. The subjects performed cycle exercise at 60 % of VO2peak for 30 min/day, 3 days/week as the endurance training. After the training, VO2peak at 3 wk-T and 6 wk-T were significantly increased compared to pre-training (Pre-T) and VO2peak at 6 wk-T was significantly increased compared to 3 wk-T. Mean SmO2 within measurement sites at VO2peak was significantly decreased after 3 wk-T and 6 wk-T compared to Pre-T, but mean SmO2 was not significantly different between 3 wk-T and 6 wk-T. Conversely, the heterogeneity of the SmO2 during exercise was not significantly changed through endurance training. A significantly negative correlation was found between ΔVO2 and ΔSmO2 after the first 3 weeks of endurance training. In contrast, no correlation was found betweenΔVO2 and ΔSmO2 after the last 3 weeks of endurance training. These results suggest that the enhanced muscle O2 availability may be one of the primary factors in increasing VO2peak after the first 3 weeks of endurance training.

An increase in the incidence rate of cardiovascular disease is attributed to high daily sitting time, while a drop in risk of cardiovascular disease comes from a decrease in daily sitting time, rather than an increase in physical activity levels. Although short-duration passive exercise increases energy expenditure and blood flow, few studies have reported on the responses of cardiorespiratory dynamics to long-duration passive exercise. The purpose of this study was to consider the effect of long-duration passive exercise for 20 min on cardiorespiratory and muscle oxygen dynamics. Eight healthy men continuously performed passive exercise using a cycle ergometer for 20 min at 50 rpm. Changes in oxygen uptake, cardiac output and muscle oxygenation were measured during passive cycling exercise. The oxygen uptake at 1 min after the start of passive exercise was significantly increased, compared to resting level, but subsequently returned to the same as resting level. Cardiac output showed no change during passive cycling exercise. Tissue oxygen saturation increased after the start of passive exercise and subsequently maintained steady state. These results suggest that the effect of increases in energy expenditure was not maintained by passive exercise for 20 min. In addition, it is likely that passive cycling exercise for 20 min has an effect on peripheral circulation, although the exercise seems to have no effect on central circulation.