Mathematical model to estimate the increase in firefighters' core temperature during firefighting activity with a portable calorimeter.

We developed a mathematical model to estimate the increase in firefighters' core body temperature from energy expenditure (EE) measured by accelerometry to prevent heat illness during firefighting. Wearing firefighter personal protective equipment, seven male subjects aged 23-42 years underwent a graded walking test on a treadmill while esophageal temperature (Tes) and skin temperature were measured with thermocouples and EE was measured with a tri-axial accelerometer. To estimate the increase in Tes from EE, we proposed a mathematical model composed of the heat capacity of active muscles (C1, kcal·°C-1), the heat capacity of the sum of resting muscles and skin (C2), the resistance to heat flux from C1 to C2 (R1, °C·min·kcal-1), and the resistance from C2 to the skin surface (R2). We determined the parameters while minimizing the differences between the estimated and measured changes in Tes profiles during graded walking. We found that C1 and C2 in individuals were highly correlated with their body weight (kg) and body surface area (m2), respectively, whereas R1 and R2 were similar across subjects. When the profiles of measured Tes (y) and estimated Tes (x) were pooled in all subjects, they were almost identical and were described by a regression equation without an intercept, y = 0.96x (r = 0.96, P < 0.0001), with a mean difference of - 0.01 ± 0.12 °C (mean ± SD) ranging from - 0.18 to 1.56 °C of the increase in Tes by Bland-Altman analysis. Thus, the model can be used for firefighters to prevent heat illness during firefighting.

Rapid saline infusion and/or drinking enhance skin sympathetic nerve activity components reduced by hypovolaemia and hyperosmolality in hyperthermia.

KEY POINTS: In hyperthermia, plasma hyperosmolality suppresses both cutaneous vasodilatation and sweating responses and this suppression is removed by oropharyngeal stimulation such as drinking. Hypovolaemia suppresses only cutaneous vasodilatation, which is enhanced by rapid infusion in hyperthermia. Our recent studies suggested that skin sympathetic nerve activity (SSNA) involves components synchronized and non-synchronized with the cardiac cycle, which are associated with an active vasodilator and a sudomotor, respectively. In the present study, plasma hyperosmolality suppressed both components; drinking removed the hyperosmolality-induced suppressions, simultaneously with increases in cutaneous vasodilatation and sweating, while not altering plasma volume and osmolality. Furthermore, a rapid saline infusion increased the synchronized component and cutaneous vasodilatation in hypovolaemic and hyperthermic humans. The results support our idea that SSNA involves an active cutaneous vasodilator and a sudomotor, and that a site where osmolality signals are projected to control thermoregulation is located more superior than the medulla where signals from baroreceptors are projected. ABSTRACT: We reported that skin sympathetic nerve activity (SSNA) involved components synchronized and non-synchronized with the cardiac cycle; both components increased in hyperthermia and our results suggested that the components are associated with an active vasodilator and a sudomotor, respectively. In the present study, we examined whether the increases in the components in hyperthermia would be suppressed by plasma hyperosmolality simultaneously with suppression of cutaneous vasodilatation and sweating and whether this suppression was released by oropharyngeal stimulation (drinking). Also, effects of a rapid saline infusion on both components and responses of cutaneous vasodilatation and sweating were tested in hypovolaemic and hyperthermic subjects. We found that (1) plasma hyperosmolality suppressed both components in hyperthermia, (2) the suppression was released by drinking 200 mL of water simultaneously with enhanced cutaneous vasodilatation and sweating responses, and (3) a rapid infusion at 1.0 and 0.2 ml min-1  kg-1 for the first 10 min and the following 20 min, respectively, increased the synchronized component and cutaneous vasodilatation in diuretic-induced hypovolaemia greater than those in a time control; at 0.1 ml min-1  kg-1 for 30 min no greater increases in the non-synchronized component and sweating responses were observed during rapid infusion than in the time control. The results support the idea that SSNA involves components synchronized and non-synchronized with the cardiac cycle, associated with the active cutaneous vasodilator and sudomotor, and a site of osmolality-induced modulation for thermoregulation is located superior to the medulla where signals from baroreceptors are projected.

Barometric pressure change and heart rate response during sleeping at ~ 3000 m altitude.

We investigated effects of change in barometric pressure (P B) with climate change on heart rate (HR) during sleep at 3000 m altitude. Nineteen healthy adults (15 males and four females; mean age 32 years) participated in this study. We measured P B (barometry) and HR (electrocardiography) every minute during their overnight stay in a mountain lodge at ~ 3000 m. We also measured resting arterial oxygen saturation (SpO2) and evaluated symptoms of acute mountain sickness (AMS) by using the Lake Louise Questionnaire at 2305 and 3000 m, respectively. P B gradually decreased during the night at the speed of approximately - 0.5 hPa/h. We found that HR during sleep decreased linearly as P B decreased in all subjects, with significance (r = 0.492-0.893; all, P < 0.001). Moreover, cross correlation analysis revealed that HR started to decrease after ~ 15 min following the decrease in P B, on average. SpO2 was 93.8 ± 1.7% at 2305 m before climbing, then decreased significantly to 90.2 ± 2.2% at the lodge before going to bed, and further decreased to 87.5 ± 2.7% after waking (all, P < 0.05). Four of the 19 subjects showed a symptom of AMS after waking (21%). Further, the decrease in HR in response to a given decrease in P B (ΔHR/ΔPB) was negatively related with a decrease in SpO2 from before going to bed to after waking at 3000 m (r = - 0.579, P = 0.009) and with total AMS scores after waking (r = 0.489, P = 0.033).

Seasonal influence on adherence to and effects of an interval walking training program on sedentary female college students in Japan.

Habitual exercise training is recommended to young people for their health promotion, but adherence may be influenced by atmospheric temperature (T a ) if performed outdoors. We compared the adherence to and the effects of a home-based interval walking training (IWT) program on sedentary female college students between winter and summer. For summer training over 176 days, 48 subjects (18-22 years old) were randomly divided into two groups: the control group (CNTsummer, n = 24), which maintained a sedentary lifestyle as before, and the IWT group (IWTsummer, n = 24), which performed IWT while energy expenditure was monitored by accelerometry. For winter training over 133 days, another group of 47 subjects (18-24 years old) was randomly divided into CNTwinter (n = 24) and IWTwinter (n = 23), as in summer. The peak T a per day was 26 ± 6 °C (SD) (range of 9-35 °C) in summer, much higher than 7 ± 5 °C (range of - 3-20 °C) in winter (P < 0.001). During a ~ 50-day vacation period, participants walked 2.1 ± 0.3 (SE) days/week in IWTsummer, less than 4.2 ± 0.3 days/week in IWTwinter (P < 0.001), with half of the energy expenditure/week for fast walking during the winter vacation (P < 0.02), whereas both IWT groups walked ~ 2 days/week during a school period (P > 0.8). After training, the peak aerobic capacity and knee flexion force increased in IWTwinter (P < 0.01) but not in CNTwinter (P > 0.3). Conversely, these parameters decreased in the summer groups. Thus, the adherence to and effects of IWT on sedentary female college students in Japan decreased in summer at least partially due to a high T a .

Effects of postural change from supine to head-up tilt on the skin sympathetic nerve activity component synchronised with the cardiac cycle in warmed men.

KEY POINTS: Humans are unique in controlling body temperature in a hot environment by a large amount of skin blood flow; however, the decrease in total peripheral resistance due to systemic cutaneous vasodilatation and the reduction of venous return to the heart due to blood pooling in the cutaneous vein threatens blood pressure maintenance in the upright position, and occasionally causes heat syncope. Against this condition, cutaneous vasodilatation is reportedly suppressed to maintain arterial pressure; however, the nerve activity responsible for this phenomenon has not been identified. In the present study, we found that the skin sympathetic nerve activity component that was synchronised with the cardiac cycle increased in hyperthermia, but the increase was suppressed when the posture was changed from supine to head-up tilt. The profile of the component agreed with that of cutaneous vasodilatation. Thus, the component might contribute to the prevention of heat syncope in humans. ABSTRACT: In humans, the cutaneous vasodilatation response to hyperthermia has been suggested to be suppressed by baroreflexes to maintain arterial pressure when the posture is changed from supine to upright, and if the reflexes do not function sufficiently, it can cause heat syncope. However, the efferent signals of the reflexes have not been identified. To identify the signals, we continuously measured skin sympathetic nerve activity (SSNA; microneurography), right atrial volume (RAV; echocardiography, the baroreceptors for the reflexes are reportedly located in the right atrium), cutaneous vascular conductance on the chest (CVCchest ; laser Doppler flowmetry), and oesophageal temperature (Toes ; thermocouple) in young men before and after passive warming with a perfusion suit, during which periods the posture was changed from supine to 30 deg head-up tilt positions. During these periods, we also simultaneously measured muscle sympathetic nerve activity (MSNA) to distinguish the SSNA from MSNA. We found that an increase in Toes by ∼0.7°C (P < 0.0001) increased the total SSNA (P < 0.005); however, the head-up tilt in hyperthermia did not change the total SSNA (P > 0.26) although an increase in CVCchest (P < 0.019) was suppressed and RAV was reduced (P < 0.008). In contrast, the SSNA component synchronised with the cardiac cycle increased in hyperthermia (P < 0.015), but decreased with the postural change (P < 0.017). The SSNA component during the postural change before and after warming was highly correlated with the CVCchest (r = 0.817, P < 0.0001), but the MSNA component was not (r = 0.359, P = 0.085). Thus, the SSNA component synchronised with the cardiac cycle appeared to be involved in suppressing cutaneous vasodilatation during postural changes.

Interval Walking Training Can Increase Physical Fitness in Middle-Aged and Older People.

No long-term exercise training regimen with high adherence and effectiveness for middle-aged and older individuals is currently broadly available in the field. To address this problem, we developed an exercise training system comprising interval walking training and an information technology network that requires only minimal staff support. We hypothesized that our training system could increase physical fitness in older people.

Target intensity and interval walking training in water to enhance physical fitness in middle-aged and older women: a randomised controlled study.

PURPOSE: To determine the target intensity for fast walking during interval walking training (IWT) in water for middle-aged and older people to enhance physical fitness. METHODS: Thirty-one women [59 ± 5 (SD) years old] were randomly divided into two groups: IWT on land (LG, N = 15) and in water (WG, N = 16). All subjects were instructed to perform ≥ 6 sets of fast and slow walking for 3 min each in a day, ≥ 4 days week(-1), for 8 weeks, at an intensity 35% higher than the oxygen consumption rate at the gas exchange threshold (VO2GET), with a subjective feeling of 16-18 points of the Borg scale during fast walking in each condition. Before and after IWT, we measured VO2GET, peak aerobic capacity (VO2peak) by graded walking and cycling tests on land and isometric knee extension (F EXT) and flexion (F FLX) forces. RESULTS: Before IWT, the VO2GET for walking in water was 14% higher and the heart rate (HR) at a given VO2 was ~10 beats min(-1) lower (P=0.001) than on land. During IWT, subjects in both groups performed IWT for ~4 days week(-1)(P > 0.9) with a 14% higher fast walking intensity in WG than in LG (P < 0.05). After IWT, the VO2peak and VO2GET for cycling, F EXT and F FLX increased more in WG than in LG (all, P < 0.05). CONCLUSION: Walking in water elevated VO2GET and decreased HR at a given exercise intensity in middle-aged and older women, which enabled them to perform exercise at a higher metabolic rate than on land due to improved subjective feelings, which, for these subjects, resulted in greater gains in physical fitness.

Comparison of alterations in cerebral hemoglobin oxygenation in late life depression and Alzheimer's disease as assessed by near-infrared spectroscopy.

BACKGROUND: Patients with Alzheimer's disease (AD) often present with apathy symptoms resembling the decreased motivation observed in depressed patients. Therefore, differentiating the initial phase of AD from late life depression may be difficult in some cases. Near-infrared spectroscopy (NIRS) is a functional neuroimaging modality that uses near-infrared light to measure changes in hemoglobin concentration on the cortical surface during activation tasks. The objective of this study was to investigate differences in brain activation associated with late life depression and with AD by means of NIRS. METHODS: NIRS was performed in 30 patients with depression, 28 patients with AD, and 33 healthy controls, all aged 60 years or older. During two tasks, a verbal fluency task and a visuospatial task, changes in oxygenated hemoglobin concentration in the frontal and parietal cortices were investigated. RESULTS: In the visuospatial task, cortical activation was lower in the depressed group than in the AD group, and significant differences were observed in the parietal cortex. CONCLUSIONS: NIRS can detect differences in brain activation between patients with late life depression and those with AD. NIRS is a promising tool for the differential diagnosis of late life depression and AD.

Health benefits of interval walking training.

Interval walking training (IWT) is a free-living training intervention involving alternating fast and slow walking cycles. IWT is efficacious in improving physical fitness and muscle strength, and reducing factors associated with lifestyle-related diseases. In individuals with type 2 diabetes, IWT improves glycemic control directly through enhanced glucose effectiveness, challenging conventional views on mechanisms behind training-induced improvements in glycemic control. Whereas adherence to IWT in short-term studies is high, ensuring long-term adherence remains a challenge, particularly in populations with chronic diseases and/or overweight/obesity. Long-term studies in real-world settings are imperative to ascertain the widespread effectiveness of IWT and elucidate its impact on hard endpoints.

Voluntary locomotion linked with cerebral activation is mediated by vasopressin V1a receptors in free-moving mice.

We previously reported that cerebral activation suppressed baroreflex control of heart rate (HR) at the onset of voluntary locomotion. In the present study, we examined whether vasopressin V1a receptors in the brain were involved in these responses by using free-moving V1a receptor knockout (KO, n = 8), wild-type mice locally infused with a V1a receptor antagonist into the nucleus tractus solitarii (BLK, n = 8) and control mice (CNT, n = 8). Baroreflex sensitivity (HR/MAP) was determined from HR response (HR) to a spontaneous change in mean arterial pressure (MAP) every 4 s during the total resting period, which was ∼8.7 h, of the 12 h measuring period in the three groups. HR/MAP was determined during the periods when the cross-correlation function (R(t)) between HR and MAP was significant (P < 0.05). Cerebral activity was determined from the power density ratio of to δ wave band (/δ) on the electroencephalogram every 4 s. Spontaneous changes in /δ were significantly correlated with R(t) during 62 ± 3% of the total resting period in CNT (P < 0.05), but only 38 ± 4% in KO and 47 ± 2% in BLK (vs. CNT, both P < 0.001). When R(t) and HR/MAP were divided into six bins according to the level of /δ, both were positively correlated with /δ in CNT (both P < 0.001), while neither was correlated in KO or BLK (all P > 0.05). Moreover, the probability that mice started to move after an increase in /δ was 24 ± 4% in KO and 24 ± 6% in BLK, markedly lower than 61 ± 5% in CNT (both P < 0.001), with no suppression of the baroreflex control of HR. Thus, central V1a receptors might play an important role in suppressing baroreflex control of HR during cerebral activation at the onset of voluntary locomotion.

Potential of collagen-like triple helical peptides as drug carriers: Their in vivo distribution, metabolism, and excretion profiles in rodents.

Collagen-model peptides composed of (X-Y-Gly)n sequences were used to study the triple helical structure of collagen. We report the stability of these collagen-like peptides in biological fluids, and their pharmacokinetics including distribution, metabolism, and excretion in animals. A typical collagen-model peptide, H-(Pro-Hyp-Gly)10-OH, was found to be extremely stable in the plasma and distributed mainly in the vascular blood space, and was eliminated through glomerular filtration in the kidneys. Triple helical peptides of (X-Y-Gly)n sequences were quantitatively recovered from the urine of rats after intravenous injection regardless of the differences in peptide net charge between -3 and +6 per triple helix. In contrast, the renal clearance became less efficient when the number of triplet repeats (n) was 12 or more. We also demonstrated the application of a collagen-like triple helical peptide as a novel drug carrier in the blood with a high urinary excretion profile. We further demonstrated that a collagen-like triple helical peptide conjugated to a spin probe, PROXYL, has the potential to evaluate the redox status of oxidative stress-induced animals in vivo.

Interval walking training in type 2 diabetes: A pilot study to evaluate the applicability as exercise therapy.

There are few established easy-to-perform exercise protocols with evidence-based effects for individuals with type 2 diabetes (T2D). A unique exercise regimen, interval walking training (IWT), has been reported to be beneficial for improving metabolic function, physical fitness and muscle strength in adults of overall health. This pilot study aims to demonstrate descriptive statistics of IWT adherence and changes in various data before and after the intervention of IWT in adults with T2D, perform statistical hypothesis testing, and calculate effect sizes. We performed a single-arm interventional pilot study with IWT for 20 weeks. We enrolled 51 participants with T2D aged 20-80 years with glycohemoglobin (HbA1c) levels of 6.5-10.0% (48-86 mmol/mol) and a body mass index of 20-34 kg/m2, respectively. The target was 60 min/week of fast walking for 20 weeks. The participants visited the hospital and were examined at 4-week intervals during this period. Between the start of IWT and after 20 weeks, we measured and evaluated changes in glucose and lipid metabolism data, body composition, physical fitness, muscle strength, dietary calorie intake, and daily exercise calories. All included participants completed IWT, with 39% of them reaching the target length of fast walking over 1,200 minutes in 20 weeks. In the primary outcome, HbA1c levels, and in the secondary, lipid metabolism and body composition, no significant changes were observed except for high-density lipoprotein cholesterol (HDL-C) (from 1.4 mmol/L to 1.5 mmol/L, p = 0.0093, t-test). However, in the target achievement group, a significant increase in VO2 peak by 10% (from 1,682 mL/min to 1,827 mL/min, p = 0.037, t-test) was observed. Effect sizes were Cohen's d = 0.25 of HDL-C, -0.55 of triglyceride, and 0.24 of VO2 peak in the target achievement group, which were considered to be of small to medium clinical significance. These results could be solely attributed to IWT since there were no significant differences in dietary intake and daily life energy consumption before and after the study. IWT could be highly versatile and was suggested to have a positive effect on lipid metabolism and physical fitness. In future randomized controlled trial (RCT) studies, the detailed effects of IWT, focusing on these parameters, will be examined. Trial registration: This trial was registered with the Japanese University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR: Usefulness on interval walking training in patients with type 2 diabetes. 000037303).

Enhanced renal Na+ reabsorption by carbohydrate in beverages during restitution from thermal and exercise-induced dehydration in men.

We examined whether carbohydrate in beverages accelerated fluid retention during recovery from thermal and exercise-induced dehydration and whether it was caused in part by an enhanced renal Na+ reabsorption rate due to insulin secretion. After dehydrating by ∼2.3% body weight by exercise in a hot environment, seven young men underwent high-carbohydrate, low-carbohydrate, or control rehydration trials by drinking one of three beverages with 3.4 g glucose + 3.1 g fructose, 1.7 g glucose + 1.6 g fructose, or 0.0 g glucose + 0.0 g fructose per deciliter, respectively, in a common composition of electrolyte solution: 21 meq/l [Na+], 5 meq/l [K+], 16.5 meq/l [Cl-], 10 meq/l [citrate(-3)]. They drank the same amount of beverage as total body weight loss within 30 min. During the 60 min before the start of drinking and the following 180 min, we measured plasma volume (PV), plasma glucose ([Glc]p), serum insulin ([Ins]s), plasma Na+ concentrations, and the renal clearances of inulin, lithium, and Na+ with plasma vasopressin ([AVP]p) and aldosterone concentrations ([Ald]p) every 30 min. After dehydration, PV decreased by ∼5% and plasma osmolality increased by ∼6 mosmol/kg H2O in all trials with no significant differences among them. We found in the high-carbohydrate trial that 1) PV increased faster than in the control trial and remained at the higher level than other trials for the last 60 min (P < 0.05); 2) accumulated urine volume was smallest after 90 min (P < 0.05); 3) the renal Na+ reabsorption rate was greatest for the first 120 min (P < 0.05); 4) during which period [AVP]p and [Ald](p) were not significantly different from other trials (both, P > 0.9); and 5) [Glc](p) and [Ins]s were highest from 45 to 105 min (P < 0.05) during rehydration. Thus carbohydrate in beverages enhances renal Na+ reabsorption, and insulin is possibly involved in this enhancement.

Energy expenditure during 2-day trail walking in the mountains (2,857 m) and the effects of amino acid supplementation in older men and women.

We compared relative exercise intensity and active energy expenditure (AEE) on trail walking in the mountains, with those of daily exercise training, and whether branched-chain amino acid (BCAA) and arginine supplementation attenuated the release of markers indicating muscle damage and declines in physical performance. Twenty-one subjects (~63 years) were divided into two groups: amino acid (AA, 51 g of amino acids and 40 g of carbohydrate, male/female = 6/4) or placebo (PL, 91 g of carbohydrate, male/female = 6/5) supplementation during 2 days of trail walking in the mountains. We measured heart rate (HR), AEE, fatigue sensation, water and food intake, and sweat loss during walking. In addition, we measured peak aerobic capacity [Formula: see text] and heart rate (HR(peak)) with graded-intensity walking, vertical jumping height (VJ) before and after walking. We found that average HR and AEE during uphill walking were ~100% HR(peak) and ~60% [Formula: see text], while they were ~80 and ~20% during downhill walking, respectively. Moreover, average total AEE per day was sevenfold that of their daily walking training. VJ after walking remained unchanged compared with the baseline in AA (P > 0.2), while it was reduced by ~10% in PL (P < 0.01), although with no significant difference in the reduction between the groups (P > 0.4). The responses of other variables were not significantly different between groups (all, P > 0.2). Thus, trail walking in the mountains required a high-intensity effort for older people, while the effects of BCAA and arginine supplementation were modest in this condition.

Role of linkage between cerebral activity and baroreflex control of heart rate via central vasopressin V1a receptors in food-deprived mice.

We previously reported that cerebral activation at the onset of voluntary locomotion suppressed baroreflex control of heart rate (HR) and increased arterial pressure via vasopressin V1a receptors in the brain. Here, we examined whether these responses were associated with food seeking, a motivated behavior, using free-moving wild type (WT, n = 10), V1a receptor knockout (KO, n = 9), and wild-type mice locally infused with a V1a receptor antagonist into the nucleus tractus solitarii (BLK, n = 10). For three consecutive days, mice were fed ad libitum (Fed), food deprived (FD), and refed (RF) under a dark/light cycle (1900/0700). Food was removed on day 2 and restored on day 3 at 1800. Throughout the protocol, cerebral activity was determined from the power density ratio of θ- to δ-wave band (θ/δ) by electroencephalogram every 4 s. Baroreflex was evaluated by the cross-correlation function [R(t)] between changes in HR and arterial pressure every 4 s. The cerebro-baroreflex linkage was then evaluated by the cross-correlation function between θ/δ and R(t). Behavior was recorded with CCD camera. We found that cerebro-baroreflex linkage, enhanced in WT at night after FD (P = 0.006), returned to Fed level after RF (P = 0.68). Similarly, food-seeking behavior increased after FD to a level twofold higher than during Fed (P < 0.001) and returned to Fed level after RF (P = 0.54). However, none of these changes occurred in KO or BLK (P > 0.11). Thus, the suppression of baroreflex control of HR linked with cerebral activation via central V1a receptors might play an important role at the onset of motivated behaviors, such as food seeking induced by FD.NEW & NOTEWORTHY Motivated behaviors, characterized by goal-directed and persistent movements, are indispensable for living. However, how cerebro-cardiovascular adjustment occurs during such behaviors remains unknown. By focusing on food-seeking behavior in a food-deprived condition using free-moving mice, we found that this condition enhanced the linkage between cerebral activation and suppression of baroreflex control of heart rate through central vasopressin V1a receptors, making it easier to start motivated behaviors by enhancing pressor response.

Effects of Yogurt Intake on Cardiovascular Strain during Outdoor Interval Walking Training by Older People in Midsummer: A Randomized Controlled Study.

We examined whether post-exercise yogurt intake reduced cardiovascular strain during outdoor interval walking training (IWT) in older people during midsummer. The IWT is a training regimen repeating slow and fast walking at ~40% and ≥70% peak aerobic capacity, respectively, for 3 min each per set, ≥5 sets per day, and ≥4 days/wk. We randomly divided 28 male and 75 female older people (~73 yr), who had performed IWT ≥12 months, into a carbohydrate group (CHO-G) consuming jelly (45 g CHO, 180 kcal) and a yogurt group (YGT-G) consuming a yogurt drink (9.3 g protein, 39 g CHO, 192 kcal) immediately after daily IWT for 56 days while monitoring exercise intensity and heart rate (HR) with portable devices. We analyzed the results in 39 subjects for the CHO-G and 37 subjects for the YGT-G who performed IWT ≥ 4 days/wk, ≥60 min total fast walking/wk, and ≥4 sets of each walk/day. We found that the mean HR for fast walking decreased significantly from the baseline after the 30th day in the YGT-G (p < 0.03), but not in the CHO-G (p = 1.00). There were no significant differences in training achievements between the groups. Thus, post-exercise yogurt intake might reduce cardiovascular strain during outdoor walking training in older people.

New portable device for continuous measurement of sweat rate under heat stress during field tests.

We have developed a portable method to measure sweat rate (SR) under heat stress during field tests. We randomly divided 15 males and 17 females (23-78 yr) into a group, equation group (EG) to determine an equation to convert a unit of SR (mmHg) by the portable method to that (mg·min-1·cm-2) by the ventilation method, and another group, validation group (VG) to validate the equation. Since we repeated measurements twice in three subjects, we randomly assigned the two measurements to one of the two groups and analyzed the results in 18 and 17 subjects for EG and VG, respectively. Subjects cycled for 20 min at moderate intensity in a warm environment while chest SR was simultaneously measured with a capsule installed with 4.8 g of silica gel and two microfans (8.4 cm3 volume) and with another capsule (12.6 cm2 area) ventilated with dry air at 1.5 L·min-1. Since the esophageal temperature (Tes) threshold for increasing SR and the slope of SR at a given increase in Tes by the portable method (x) were in high agreement with those values obtained by the ventilation method (y) in both groups (all r > 0.88, P < 0.001), we determined regression equations for all subjects after pooling data from both groups: y = 1.11x - 3.99 and y = 1.05x + 0.01 when the 95% prediction limits were ±0.12°C and ±0.43 mg·min-1·cm-2·°C-1 with minimum mean differences over the range of 36.2°C-37.2°C and 0.2-2.4 mg·min-1·cm-2·°C-1, respectively, using Bland-Altman analysis. Based on these findings, we consider the portable device to be reliable enough to evaluate individual sweating capacity during field tests.NEW & NOTEWORTHY We developed a portable device to measure sweat rate continuously under heat stress during field tests, with precision similar to that obtained by the ventilation method, which has been used to evaluate individual sweat rate responses in laboratory tests. This new, portable device will provide more opportunities to determine factors influencing sweat rate in larger populations of subjects during field tests.

Effects of Interval Walking Training on Oral Health Status in Middle-Aged and Older Adults: A Case-Control Study.

The purpose of this study was to determine the effect of walking training "Interval Walking Training (IWT)" on oral health status. Participants were divided into two groups: an exercise intervention group and a non-intervention group (control). The intervention group consisted of 59 subjects (20 males, 39 females) aged 50 years or older who participated in the IWT program in Matsumoto from 2019 to April 2022. The control group consisted of 33 subjects (14 males and 19 females) aged 50 years or older who have visited Niigata University Medical and Dental Hospital and agreed to participate in the study. The intervention group underwent walking training (interval walking training) for at least 5-6 months. The walking training consisted of five sets of fast walking above 70% peak aerobic capacity for walking (VO2peak) for 3 min, followed by 3 min of slow walking at ~40% VO2 peak per day for more than four days/week. The oral health status was evaluated for the number of teeth, occlusal force, salivary occult blood, masticatory performance, and tongue pressure. A total of 57 participants were analyzed in the intervention group (18 males and 39 females, age: 66.7 ± 0.8 (mean ± S.E.) years) and 33 participants in the control group (14 males and 19 females, age: 74.5 ± 1.1 (mean ± S.E.) years). There were no significant differences in gender, salivary occult blood, tongue pressure, masticatory performance, or occlusal force between the two groups at the start of the intervention (p = 0.36, p = 0.48, p = 0.42, p = 0.58, and p = 0.08, respectively by unpaired t-test or χ2 test). On the other hand, there were significant differences in age and BMI, with a trend toward lower age and higher BMI in the intervention group (p < 0.001 and p < 0.001, respectively, by unpaired t-test). In terms of rate of change, the intervention group showed a significant increase in occlusal force (F = 4.5, p = 0.04, ANCOVA) and a significant decrease in BMI (F = 7.3, p = 0.009, ANCOVA). No significant differences were observed in the other measured items. It was found that walking training in both middle-aged and older people does not only affect the physical aspect of weight loss but may help maintain and improve the occlusal force.

Skin sympathetic nerve activity component synchronizing with cardiac cycle is involved in hypovolaemic suppression of cutaneous vasodilatation in hyperthermia.

Although cutaneous vasodilatation in hyperthermia was suppressed during hypovolaemia, the efferent neural pathway mediating this suppression has not been identified. To determine the electrical nerve signals which account for the suppression of cutaneous vasodilatation during hypovolaemia, skin sympathetic nerve activity (SSNA; microneurography) from the peroneal nerve, laser-Doppler blood flow (LDF) on the ipsilateral dorsal foot, mean arterial pressure (MAP; sonometry) and oesophageal temperature (T(oes)) were measured before and during 45 min of passive warming in 20 healthy subjects during normovolaemia (n = 10) or hypovolaemia (n = 10) conditions. Hypovolaemia was achieved by diuretic administration. Cutaneous vascular conductance (CVC = LDF/MAP), SSNA burst frequency and total SSNA obtained from rectified and filtered SSNA signal increased as T(oes) increased by ~0.5°C by the end of warming in both groups. The increase in CVC was significantly lower in hypovolaemia than normovolaemia (P < 0.0001), but with no significant difference in the increase in burst frequency and total SSNA between groups (P > 0.32). However, using an alternative analysis that constructed spike incidence histograms from the original signal using 0.05 s bins during the 5 s following a given R-wave, we found a SSNA component synchronized with the cardiac cycle with a 1.1-1.3 s latency. This component increased with an increase in T(oes) and the increase was significantly suppressed by hypovolaemia (P < 0.0001). In conclusion, hypovolaemic suppression of cutaneous vasodilatation during hyperthermia might be caused by a reduction in the SSNA component synchronized with cardiac cycle.

Effect of Carbohydrate-Electrolyte Solution Including Bicarbonate Ion Ad Libitum Ingestion on Urine Bicarbonate Retention during Mountain Trekking: A Randomized, Controlled Pilot Study.

We investigated whether bicarbonate ion (HCO3-) in a carbohydrate-electrolyte solution (CE+HCO3) ingested during climbing to 3000 m on Mount Fuji could increase urine HCO3- retention. This study was a randomized, controlled pilot study. Sixteen healthy lowlander adults were divided into two groups (six males and two females for each): a tap water (TW) group (0 kcal with no energy) and a CE+HCO3 group. The allocation to TW or CE+HCO3 was double blind. The CE solution contains 10 kcal energy, including Na+ (115 mg), K+ (78 mg), HCO3- (51 mg) per 100 mL. After collecting baseline urine and measuring body weight, participants started climbing while energy expenditure (EE) and heart rate (HR) were recorded every min with a portable calorimeter. After reaching a hut at approximately 3000 m, we collected urine and measured body weight again. The HCO3- balance during climbing, measured by subtracting the amount of urine excreted from the amount of fluid ingested, was -0.37 ± 0.77 mmol in the CE+HCO3, which was significantly higher than in the TW (-2.23 ± 0.96 mmol, p < 0.001). These results indicate that CE containing HCO3- supplementation may increase the bicarbonate buffering system during mountain trekking up to ~3000 m, suggesting a useful solution, at least, in the population of the present study on Mount Fuji.