Corrigendum: Gravity-Induced Lower-Leg Swelling Can Be Ameliorated by Ingestion of α-Glucosyl Hesperidin Beverage.

[This corrects the article DOI: 10.3389/fphys.2021.670640.].

Gravity-Induced Lower-Leg Swelling Can Be Ameliorated by Ingestion of α-Glucosyl Hesperidin Beverage.

The most likely cause of lower-leg swelling is prolonged sitting, which sometimes induces deep vein thrombosis, also known as, economy class syndrome. We aimed to clarify the influence of intake of 4 G -α-glucopyranosyl hesperidin (G-Hsp) beverage on the lower-leg swelling caused by 6 h of sitting in six healthy women. All subjects ingested 100 mL of G-Hsp or Placebo beverages with 100 mL of mineral water after 10 min of rest in a chair. Subsequently, subjects were requested to sit in the chair in a relaxed position for 6 h with two breaks to walk for urination. Calf water content measured by impedance plethysmography, calf circumference, and calf skin temperature by infrared thermography were measured, along with assessment of calf swelling sensation on a visual analog scale. Increase in ankle % circumference was significantly less after the G-Hsp ingestion (101.8 ± 1.5%) than after placebo (103.3 ± 0.8%; P = 0.004). A significant difference was found between percent circumference after the G-Hsp and the placebo, that is, the calf swelling after the placebo was significantly larger (P = 0.043). A gradual increase in skin temperature at the lower limb was observed after G-Hsp ingestion, while there was no change after placebo. Gravity-induced calf and ankle swelling resulted by prolonged sitting can be ameliorated by oral ingestion of hesperidin-derived G-Hsp through production of nitric oxide. It might be helpful in preventing economy-class syndrome caused by enforced sitting for a long duration.

Effects of catechin-enriched ion beverage intake on thermoregulatory function in a hot environment.

We examined the effect of intake of a catechin-enriched ion beverage (Cat-I) on the thermoregulatory response in a hot environment. Eight healthy men were exposed to a hot environment for 90 min at an ambient temperature of 35 °C (relative humidity: 75%) combined with lower leg water immersion at 40 °C. At that time, either Cat-I, an ion beverage (Ion), or mineral water (Placebo) was consumed at three points: (1) at the start of lower leg immersion, (2) at 30 min after immersion, and (3) at 60 min after immersion. In all conditions, tympanic temperature (Tty) increased gradually during lower leg water immersion. However, the rate of increase of Tty tended to be suppressed after 30 min. The effect of drinking Cat-I had a limited detection period of approximately 60-70 min, and the rate of sweating was clearly increased with Cat-I compared with Ion and Placebo. Cat-I also tended to decrease the body temperature threshold at which sweating was induced compared with Ion or Placebo. These findings suggest that Cat-I efficiently suppressed the increase of body temperature in a hot environment.

Effect of spraying of fine water particles on facial skin moisture and viscoelasticity in adult women.

BACKGROUND/PURPOSE: It is known that the elderly and adult women with reduction in sebum secretion have reduced skin barrier function, drying of the skin in a low humidity environment is accompanied by physiological distress. As our hypothesis, when fine water particles are sprayed on the skin, the water content of the corneal layer is significantly increased. In the present study, we examined the ability of fine water particles to improve facial skin moisture levels in adult women. METHODS: We examined skin conductance, transepidermal water loss (TEWL), and skin elasticity as an index of skin barrier function at the cheek in 17 healthy adult women in the spraying of fine water particles, in the environment temperature at 24°C and 34.5% relative humidity. RESULTS: The skin conductance of stratum corneum after 120 minute of spraying, A condition (peak particle size below 0.5 µm) was 119.7 ± 25.1%, B condition (peak particle size 1.8 µm) was 100.4 ± 31.7%, C condition (peak particle size 5.4 µm) was 110.1 ± 25.0%, and the A condition was significantly higher than the B condition. Also, skin elasticity in the A condition tended to be higher value than in the other conditions. Transepidermal water loss (TEWL) after 120 minute of spraying showed a lower value in the A condition than in the other conditions. In the A condition, the skin conductance steadily maintained their initial levels up to 360 minute after spraying. CONCLUSION: Especially, by spraying smallest fine water particles, skin barrier function at the cheek was improved. These data indicated that non-charged fine water particles played an important role on moisten skin in a low humidity environment.

Elevated sympathetic vasomotor outflow in response to increased inspiratory muscle activity during exercise is less in young women compared with men.

NEW FINDINGS: What is the central question of this study? Premenopausal women have an attenuated inspiratory muscle metaboreflex-induced increase in arterial blood pressure compared with men. It is unclear whether sympathetic vasomotor outflow during dynamic exercise with increased inspiratory muscle activation is less in young women than in men. What is the main finding and its importance? The magnitude of increased sympathetic vasomotor outflow during leg cycling with inspiratory resistance was smaller in women than in men. Less sympathetic vasomotor outflow with inspiratory muscle metaboreflex activation could be one of the mechanisms for the attenuated inspiratory muscle-induced metaboreflex during exercise in young women. ABSTRACT: We compared changes in muscle sympathetic nerve activity (MSNA) and cardiovascular variables during leg cycle exercise with increased inspiratory muscle resistance in men and women. We hypothesized that sympathetic vasomotor outflow during exercise with increased inspiratory resistance would be attenuated in young women compared with age-matched men. Eight women and seven men completed the study. The subjects performed two 10 min exercise bouts at 40% peak oxygen uptake using a cycle ergometer in a semirecumbent position [spontaneous breathing for 5 min and voluntary hyperventilation with or without inspiratory resistive breathing for 5 min (breathing frequency 50 breaths min-1 with a 50% duty cycle; inspiratory resistance 30% of maximal inspiratory pressure)]. Mean arterial blood pressure (MAP) was acquired using finger photoplethysmography. The MSNA was recorded via microneurography of the right median nerve at the cubital fossa. During leg cycle exercise with inspiratory resistive breathing, MSNA burst frequency was increased, accompanied by an increase in MAP in both men and women. Women, compared with men, had less of an increase in MAP (women +22.8 ± 12.3 mmHg versus men +32.2 ± 5.4 mmHg; P < 0.05) and MSNA burst frequency (women +9.6 ± 2.9 bursts min-1 versus men +14.6 ± 6.4 bursts min-1 ; P < 0.05). These results suggest that the attenuated inspiratory muscle-induced metaboreflex during exercise in young women is attributable, in part, to a lesser sympathetic vasomotor outflow compared with men.

Intracellular oxygen tension limits muscle contraction-induced change in muscle oxygen consumption under hypoxic conditions during Hb-free perfusion.

Under acute hypoxic conditions, the muscle oxygen uptake (mV˙O2) during exercise is reduced by the restriction in oxygen-supplied volume to the mitochondria within the peripheral tissue. This suggests the existence of a factor restricting the mV˙O2 under hypoxic conditions at the peripheral tissue level. Therefore, this study set out to test the hypothesis that the restriction in mV˙O2 is regulated by the net decrease in intracellular oxygen tension equilibrated with myoglobin oxygen saturation (∆PmbO2) during muscle contraction under hypoxic conditions. The hindlimb of male Wistar rats (8 weeks old, n = 5) was perfused with hemoglobin-free Krebs-Henseleit buffer equilibrated with three different fractions of O2 gas: 95.0%O2, 71.3%O2, and 47.5%O2 The deoxygenated myoglobin (Mb) kinetics during muscle contraction were measured under each oxygen condition with a near-infrared spectroscopy. The ∆[deoxy-Mb] kinetics were converted to oxygen saturation of myoglobin (SmbO2), and the PmbO2 was then calculated based on the SmbO2 and the O2 dissociation curve of the Mb. The SmbO2 and PmbO2 at rest decreased with the decrease in O2 supply, and the muscle contraction caused a further decrease in SmbO2 and PmbO2 under all O2 conditions. The net increase in mV˙O2 from the muscle contraction (∆mV˙O2) gradually decreased as the ∆PmbO2 decreased during muscle contraction. The results of this study suggest that ΔPmbO2 is a key determinant of the ΔmV˙O2.

Revised guideline for the diagnosis and treatment of acquired idiopathic generalized anhidrosis in Japan.

Acquired idiopathic generalized anhidrosis (AIGA) is characterized by an acquired impairment in total body sweating despite exposure to heat or exercise. Severe cases may result in heatstroke. Most cases of AIGA have been reported in Asia, especially in Japan. However, there is limited information on the epidemiology of this condition, and no diagnostic criteria or appropriate treatment options have been established. This guideline was developed to fill this gap. It contains information on the etiology, diagnosis, evaluation of disease severity and evidence-based recommendations for the treatment of AIGA. Appropriate treatment according to disease severity may relieve the clinical manifestations and emotional distress experienced by patients with AIGA.

Differences in autonomic neural activity during exercise between the second and third trimesters of pregnancy.

AIM: To test the hypothesis that autonomic neural activity in pregnant women during exercise varies according to gestational age. METHODS: This cross-sectional study involved 20 healthy women in their second (n = 13) or third (n = 7) trimester of pregnancy. Incremental cardiopulmonary exercise testing was performed with an electromagnetic cycle ergometer. Heart rate variability was analyzed by frequency analysis software. RESULTS: The low-frequency to high-frequency (LF/HF) ratio, an indicator of the sympathetic nervous system, was significantly higher in third trimester than in second trimester subjects (P < 0.05) at 1, 2, and 3 min of incremental exercise testing. In contrast, the HF/total power ratio, an indicator of rapidly acting parasympathetic activity, was significantly higher in second trimester than in third trimester subjects (P < 0.05) at 2 and 3 min. In addition, a negative correlation was found between gestational age and the 'accumulation half-time' of the LH/HF ratio, the time point at which the sum of the LF/HF ratio reached 50% of that accumulated in the total 6 min of exercise testing (r = -0.49, P = 0.028). CONCLUSIONS: The autonomic response to exercise in pregnant women differs between the second and third trimesters. These differences should be considered when prescribing exercise to pregnant women.

Respiratory modulation of human autonomic function on Earth.

KEY POINTS: We studied healthy supine astronauts on Earth with electrocardiogram, non-invasive arterial pressure, respiratory carbon dioxide concentrations, breathing depth and sympathetic nerve recordings. The null hypotheses were that heart beat interval fluctuations at usual breathing frequencies are baroreflex mediated, that they persist during apnoea, and that autonomic responses to apnoea result from changes of chemoreceptor, baroreceptor or lung stretch receptor inputs. R-R interval fluctuations at usual breathing frequencies are unlikely to be baroreflex mediated, and disappear during apnoea. The subjects' responses to apnoea could not be attributed to changes of central chemoreceptor activity (hypocapnia prevailed); altered arterial baroreceptor input (vagal baroreflex gain declined and muscle sympathetic nerve burst areas, frequencies and probabilities increased, even as arterial pressure climbed to new levels); or altered pulmonary stretch receptor activity (major breathing frequency and tidal volume changes did not alter vagal tone or sympathetic activity). Apnoea responses of healthy subjects may result from changes of central respiratory motoneurone activity. ABSTRACT: We studied eight healthy, supine astronauts on Earth, who followed a simple protocol: they breathed at fixed or random frequencies, hyperventilated and then stopped breathing, as a means to modulate and expose to view important, but obscure central neurophysiological mechanisms. Our recordings included the electrocardiogram, finger photoplethysmographic arterial pressure, tidal volume, respiratory carbon dioxide concentrations and peroneal nerve muscle sympathetic activity. Arterial pressure, vagal tone and muscle sympathetic outflow were comparable during spontaneous and controlled-frequency breathing. Compared with spontaneous, 0.1 and 0.05 Hz breathing, however, breathing at usual frequencies (∼0.25 Hz) lowered arterial baroreflex gain, and provoked smaller arterial pressure and R-R interval fluctuations, which were separated by intervals that were likely to be too short and variable to be attributed to baroreflex physiology. R-R interval fluctuations at usual breathing frequencies disappear during apnoea, and thus cannot provide evidence for the existence of a central respiratory oscillation. Apnoea sets in motion a continuous and ever changing reorganization of the relations among stimulatory and inhibitory inputs and autonomic outputs, which, in our study, could not be attributed to altered chemoreceptor, baroreceptor, or pulmonary stretch receptor activity. We suggest that responses of healthy subjects to apnoea are driven importantly, and possibly prepotently, by changes of central respiratory motoneurone activity. The companion article extends these observations and asks the question, Might terrestrial responses to our 20 min breathing protocol find expression as long-term neuroplasticity in serial measurements made over 20 days during and following space travel?

Respiratory modulation of human autonomic function: long-term neuroplasticity in space.

KEY POINTS: We studied healthy astronauts before, during and after the Neurolab Space Shuttle mission with controlled breathing and apnoea, to identify autonomic changes that might contribute to postflight orthostatic intolerance. Measurements included the electrocardiogram, finger photoplethysmographic arterial pressure, respiratory carbon dioxide levels, tidal volume and peroneal nerve muscle sympathetic activity. Arterial pressure fell and then rose in space, and drifted back to preflight levels after return to Earth. Vagal metrics changed in opposite directions: vagal baroreflex gain and two indices of vagal fluctuations rose and then fell in space, and descended to preflight levels upon return to Earth. Sympathetic burst frequencies (but not areas) were greater than preflight in space and on landing day, and astronauts' abilities to modulate both burst areas and frequencies during apnoea were sharply diminished. Spaceflight triggers long-term neuroplastic changes reflected by reciptocal sympathetic and vagal motoneurone responsiveness to breathing changes. ABSTRACT: We studied six healthy astronauts five times, on Earth, in space on the first and 12th or 13th day of the 16 day Neurolab Space Shuttle mission, on landing day, and 5-6 days later. Astronauts followed a fixed protocol comprising controlled and random frequency breathing and apnoea, conceived to perturb their autonomic function and identify changes, if any, provoked by microgravity exposure. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, tidal carbon dioxide concentrations and volumes, and peroneal nerve muscle sympathetic activity on Earth (in the supine position) and in space. (Sympathetic nerve recordings were made during three sessions: preflight, late mission and landing day.) Arterial pressure changed systematically from preflight levels: pressure fell during early microgravity exposure, rose as microgravity exposure continued, and drifted back to preflight levels after return to Earth. Vagal metrics changed in opposite directions: vagal baroreflex gain and two indices of vagal fluctuations (root mean square of successive normal R-R intervals; and proportion of successive normal R-R intervals greater than 50 ms, divided by the total number of normal R-R intervals) rose significantly during early microgravity exposure, fell as microgravity exposure continued, and descended to preflight levels upon return to Earth. Sympathetic mechanisms also changed. Burst frequencies (but not areas) during fixed frequency breathing were greater than preflight in space and on landing day, but their control during apnoea was sharply altered: astronauts increased their burst frequencies from already high levels, but they could not modulate either burst areas or frequencies appropriately. Space travel provokes long-lasting sympathetic and vagal neuroplastic changes in healthy humans.

Effect of micro mist sauna bathing on thermoregulatory and circulatory functions and thermal sensation in humans.

To examine the effects of micro mist sauna bathing, produced by water crushing method, we exposed ten male subjects to five cases of micro mist sauna, namely (1) room temperature (RT) 38 °C with 100 % (actually 91 %) relative humidity (RH), (2) RT 41.5 °C with 80 % (actually 81 %) RH, (3) RT 41.5 °C with 100 % (actually 96 %) RH, (4) RT 45.0 °C with 64 % (actually 61 %) RH, and (5) RT 45.0 °C with 100 % (actually 86 %) RH, and measured tympanic temperature, mean skin temperature, heart rate (HR), and cheek moisture content, as well as ratings of thermal and sweating sensation tympanic temperatures at RT 45 °C were significantly higher at 86 % RH than those at 61 % RH; however, those at RT 45 °C with 61 % RH were higher than those with 86 % RH during recovery. There were no significant differences at RT 41.5 °C between with 81 % RH and with 96 % RH. Mean skin temperature was the highest at RT 45 °C 86 % RH case, followed by at RT 41.5 °C 96 % RH, RT 45 °C 61 % RH, RT 41.5 °C 81 % RH, and finally at RT 38 °C 91 % RH. HR change showed the same order as for mean skin temperature. A significant difference in cheek moisture content was observed between RT 41.5 °C with 81 % RH and RT 45 °C with 86 % RH 10 min after the micro mist bathing. There were no significant differences between ratings of thermal sensation at RT 41.5 °C with 81 % RH and at RT 45 °C with 61 % RH and RT 45 °C with 61 % RH and RT 45 °C with 86 % RH. Between RT 45 °C with 86 % RH and RT 41.5 °C with 81 % RH, there was a tendency for interaction (0.05 < p < 0.1). Other cases showed significant higher ratings of thermal sensation at higher room temperature or higher relative humidity. The ratings of sweating sensation 10 min after the mist sauna bathing were significantly higher at higher RT and RH except between RT 41.5 °C 96 % RH and RT 45 °C 86 % RH which exhibited no significant difference. We concluded that the micro mist sauna produced by water crushing method induced more moderate and effective thermal effect during micro mist sauna bathing than the conventional mist sauna bathing. In addition, micro mist sauna is as effective for heating the human subjects as bathtub bathing as well as more moderate thermal and sweating sensations.

Effects of Defecation Strain at Various Bed Reclining Angles on Intrarectal Pressure and Cardiovascular Responses.

BACKGROUND: There is no clear information about the optimal bed reclining angle for promoting efficient and safe defecation in bedfast patients. OBJECTIVE: The aim of this study was to examine the optimal bed reclining angle for facilitating increases in intrarectal pressure without causing marked cardiovascular changes in order to develop an efficient and safe defecation position for bedfast patients. METHODS: Twelve healthy men participated in this study. The subjects were required to strain for 15 seconds at the end stage of inspiration while their bed was reclined at 0° (supine), 15°, 30°, or 60°. During straining, the subjects were asked to maintain (a) an intrarectal pressure of 20 mm Hg or (b) the maximal intrarectal pressure. Intrarectal pressure, blood pressure, heart rate, and abdominal muscle activity (electromyographic activity) were recorded continuously throughout the study period. RESULTS: During straining, intrarectal pressure increased with the reclining angle, and a significant linear correlation was detected between the sine of the reclining angle of the bed and intrarectal pressure (η = .57, p < .01). When subjects were straining with the aim of maintaining maximal intrarectal pressure, the extent of the observed changes (delta) in blood pressure and heart rate did not differ significantly across the reclining angles. When subjects were straining with the aim of maintaining an intrarectal pressure of 20 mm Hg, the delta blood pressure decreased as the reclining angle increased 0°: M = 23.7, SD = 15.3 mm Hg, 95% CI [11.9, 35.4]; 15°: M = 25.9, SD = 10.8 mm Hg, 95% CI [17.6, 34.2]; 30°: M = 17.7, SD = 9.4 mm Hg, 95% CI [10.4, 24.9]; 60°: M = 15.5, SD = 9.5 mm Hg, 95% CI [8.1, 22.8]; 15° versus 30°: p < .05; 15° versus 60°: p < .05. The amount of muscle activity observed during straining decreased as the reclining angle increased. DISCUSSION: In bedfast patients, it is suggested that higher reclining angles may enable safer and more efficient defecation, because it decreases the amount of muscle activity required to increase the intrarectal pressure and reduces the potentially deleterious effects of straining on the cardiovascular system to develop an efficient and safe defecation position for bedfast patients.

Endurance training facilitates myoglobin desaturation during muscle contraction in rat skeletal muscle.

At onset of muscle contraction, myoglobin (Mb) immediately releases its bound O2 to the mitochondria. Accordingly, intracellular O2 tension (PmbO2) markedly declines in order to increase muscle O2 uptake (mVO2). However, whether the change in PmbO2 during muscle contraction modulates mVO2 and whether the O2 release rate from Mb increases in endurance-trained muscles remain unclear. The purpose of this study was, therefore, to determine the effect of endurance training on O2 saturation of Mb (SmbO2) and PmbO2 kinetics during muscle contraction. Male Wistar rats were subjected to a 4-week swimming training (Tr group; 6 days per week, 30 min × 4 sets per day) with a weight load of 2% body mass. After the training period, deoxygenated Mb kinetics during muscle contraction were measured using near-infrared spectroscopy under hemoglobin-free medium perfusion. In the Tr group, the VmO2peak significantly increased by 32%. Although the PmbO2 during muscle contraction did not affect the increased mVO2 in endurance-trained muscle, the O2 release rate from Mb increased because of the increased Mb concentration and faster decremental rate in SmbO2 at the maximal twitch tension. These results suggest that the Mb dynamics during muscle contraction are contributing factors to faster VO2 kinetics in endurance-trained muscle.

Arousal electrical stimuli evoke sudomotor activity related to P300, and skin vasoconstrictor activity related to N140 in humans.

OBJECTIVE: Arousal stimuli evoke bursts of skin sympathetic nerve activity (SSNA). SSNA usually contains sudomotor and vasoconstrictor neural spikes. The aim of this study was to elucidate which components of event-related potentials (ERPs) are related to sudomotor and vasoconstrictor responses comprising arousal SSNA bursts. METHODS: We recorded SSNA from the tibial nerve by microneurography, with corresponding sympathetic skin response (SSR), sympathetic flow response (SFR), and ERPs in 10 healthy subjects. Electrical stimulation of the median nerve was used to induce arousal responses. ERPs were classified by the occurrence of SSR and SFR. RESULTS: SSNA bursts followed by SSR were associated with larger P300 than SSNA bursts followed by no SSR. For N140, no difference in the amplitude was found between SSNA bursts with and without SSR. SSNA bursts followed by SFR were associated with larger N140 than SSNA bursts followed by no SFR. However, there were no differences in the amplitude of P300 between SSNA bursts with and without SFR. CONCLUSIONS: Sudomotor and skin vasoconstrictor responses to arousal stimuli were differently associated with distinct ERP components. SIGNIFICANCE: The possibility that sudomotor and skin vasoconstrictor activities comprising arousal SSNA reflect different stages of the cognitive process is suggested.

Role of sympathetic nerve activity in the process of fainting.

Syncope is defined as a transient loss of consciousness and postural tone, characterized by rapid onset, short duration, and spontaneous recovery, and the process of syncope progression is here described with two types of sympathetic change. Simultaneous recordings of microneurographically-recorded muscle sympathetic nerve activity (MSNA) and continuous and noninvasive blood pressure measurement has disclosed what is going on during the course of syncope progression. For vasovagal or neurally mediated syncope, three stages are identified in the course of syncope onset, oscillation, imbalance, and catastrophe phases. Vasovagal syncope is characterized by sympathoexcitation, followed by vagal overcoming via the Bezold-Jarisch reflex. Orthostatic syncope is caused by response failure or a lack of sympathetic nerve activity to the orthostatic challenge, followed by fluid shift and subsequent low cerebral perfusion. Four causes are considered for the compensatory failure that triggers orthostatic syncope: hypovolemia, increased pooling in the lower body, failure to activate sympathetic activity, and failure of vasoconstriction against sympathetic vasoconstrictive stimulation. Many pathophysiological conditions have been described from the perspectives of (1) exaggerated sympathoexcitation and (2) failure to activate the sympathetic nerve. We conclude that the sympathetic nervous system can control cardiovascular function, and its failure results in syncope; however, responses of the system obtained by microneurographically-recorded MSNA would determine the pathophysiology of the onset and progression of syncope, explaining the treatment effect that could be achieved by the analysis of this mechanism.

Hemifacial hyperhidrosis associated with ipsilateral/contralateral cervical disc herniation myelopathy. Functional considerations on how compression pattern determines the laterality.

Sweating is an important mechanism for ensuring constant thermoregulation, but hyperhidrosis may be disturbing. We present five cases of hemifacial hyperhidrosis as a compensatory response to an/hypohidrosis caused by cervical disc herniation. All the patients complained of hemifacial hyperhidrosis, without anisocoria or blepharoptosis. Sweat function testing and thermography confirmed hyperhidrosis of hemifacial and adjacent areas. Neck MRI showed cervical disc herniation. Three of the patients had lateral compression with welldemarcated hypohidrosis below the hyperhidrosis on the same side as the cervical lesion. The rest had paramedian compression with poorly demarcated hyperhidrosis and hypohidrosis on the contralateral side. Although MRI showed no intraspinal pathological signal intensity, lateral dural compression might influence the circulation to the sudomotor pathway, and paramedian compression might influence the ipsilateral sulcal artery, which perfuses the sympathetic descending pathway and the intermediolateral nucleus. Sweat function testing and thermography should be performed to determine the focus of the hemifacial hyperhidrosis, and the myelopathy should be investigated on both sides.

A comparison of head-out mist bathing, with or without facial fanning, with head-out half-body low-water level bathing in humans--a pilot study.

To reduce the risks of Japanese-style bathing, half-body bathing (HBLB) has been recommended in Japan, but discomfort due to the cold environment in winter prevents its widespread adoption. The development of the mist sauna, which causes a gradual core temperature rise with sufficient thermal comfort, has reduced the demerits of HBLB. We examined head-out 42 °C mist bathing with 38 °C HBLB up to the navel to see if it could improve thermal comfort without detracting from the merits of HBLB, with and without the effects of facial fanning (FF). The subjects were seven healthy males aged 22-25 years. The following bathing styles were provided: (1) HBLB-head-out half-body low bathing of 38 °C up to the navel (20 min); (2) HOMB-head-out mist bathing of 42 °C and HBLB of 38 °C (20 min); and (3) HOMBFF-HOMB with FF (20 min). HOMB raised the core temperature gradually. HOMBFF suppressed the core temperature rise in a similar fashion to HOMB. Increases in blood pressure and heart rate usually observed in Japanese traditional-style bathing were less marked in HOMBs with no significant difference with and without FF. The greatest body weight loss was observed after Japanese traditional-style bathing, with only one-third of this amount lost after mist bathing, and one-sixth after HBLB. HOMB increased thermal sensation, and FF also enhanced post-bathing invigoration. We conclude that HOMB reduces the risks of Japanese traditional style bathing by mitigating marked changes in the core temperature and hemodynamics, and FF provides thermal comfort and invigoration.

Effects of isotonic and isometric exercises with mist sauna bathing on cardiovascular, thermoregulatory, and metabolic functions.

To clarify the effects of isometric and isotonic exercise during mist sauna bathing on the cardiovascular function, thermoregulatory function, and metabolism, six healthy young men (22 ± 1 years old, height 173 ± 4 cm, weight 65.0 ± 5.0 kg) were exposed to a mist sauna for 10 min at a temperature of 40 °C, and relative humidity of 100 % while performing or not performing ∼30 W of isometric or isotonic exercise. The effect of the exercise was assessed by measuring tympanic temperature, heart rate, systolic and diastolic blood pressure, chest sweat rate, chest skin blood flow, and plasma catecholamine and cortisol, glucose, lactate, and free fatty acid levels. Repeated measures ANOVA showed no significant differences in blood pressure, skin blood flow, sweat rate, and total amount of sweating. Tympanic temperature increased more during isotonic exercise, and heart rate increase was more marked during isotonic exercise. The changes in lactate indicated that fatigue was not very great during isometric exercise. The glucose level indicated greater energy expenditure during isometric exercise. The free fatty acid and catecholamine levels indicated that isometric exercise did not result in very great energy expenditure and stress, respectively. The results for isotonic exercise of a decrease in lactate level and an increase in plasma free fatty acid level indicated that fatigue and energy expenditure were rather large while the perceived stress was comparatively low. We concluded that isotonic exercise may be a more desirable form of exercise during mist sauna bathing given the changes in glucose and free fatty acid levels.

Effects of water nanodroplets on skin moisture and viscoelasticity during air-conditioning.

BACKGROUND/PURPOSE: In air-conditioned rooms, dry air exacerbates some skin diseases, for example, senile xerosis, atopic dermatitis, and surface roughness. Humidifiers are used to improve air dryness, which often induces excess humidity and thermal discomfort. To address this issue, we investigated the effects of water nanodroplets (mist) on skin hydration, which may increase skin hydration by penetrating into the interstitial spaces between corneocytes of the stratum corneum (SC) without increasing air humidity. METHODS: We examined biophysical parameters, including skin conductance and transepidermal water loss (TEWL), and biomechanical parameters of skin distension/retraction before and after suction at the forehead, lateral canthus, and cheek, with or without mist, in a testing environment (24°C, 35% relative humidity) for 120 min. RESULTS: In the group without mist, TEWL values significantly decreased at all the sites after 1 h compared with the initial values. However, in the presence of mist, TEWL values were maintained at the initial values through the test, yielding significant differences vs. the group without mist. There were no significant differences between mist and mist-free groups in terms of skin conductance. Skin distension was significantly increased in the group with mist compared with that in the group without mist at the forehead and cheek, suggesting a softening effect of mist. CONCLUSION: Skin deformation of the face was improved by mist, suggesting hydration of the SC by mist. The change in TEWL was influenced by mist, suggesting supply of water to the skin, particularly the SC, by mist. These data indicated that a mist of water nanodroplets played an important role in softening skin in an air-conditioned room without increasing excess humidity.

Arterial pressure oscillation and muscle sympathetic nerve activity after 20 days of head-down bed rest.

Both spectral power within the low-frequency component, i.e., 0.04 to 0.15 Hz, of systolic pressure and muscle sympathetic nerve activity are increased during head-up tilt. The nerve activity during tilt is altered after space flight and exposure to simulated microgravity. In the present study, correlations of the low-frequency component and the nerve activity were analyzed before and after 20 days of -6° of head-down bed rest. Measurements were performed at -6° head-down bed rest, 0° (flat), and 30° and 60° head-up tilt (HUT). Mean arterial pressure during HUT was not different between pre- and post-bed rest, but muscle sympathetic nerve activity in post-bed rest significantly increased at tilt angles of -6°, 0°, 30°, and 60° compared with those during pre-bed rest. The low-frequency component of systolic pressure also significantly increased during post-bed rest compared with pre-bed rest at tilts of 0°, 30°, and 60°. The nerve activity and the frequency component were linearly correlated for individual (r(2) = 0.51-0.88) and averaged (r(2) = 0.60) values when the values included both pre- and post-bed rest. Thus, the low-frequency component of systolic pressure could be an index of the muscle sympathetic nerve activity during tilt during pre- and post-bed rest.