Changes in the control of skin blood flow with exercise training: where do cutaneous vascular adaptations fit in?

Evaluation of a heating protocol and stocking density impact on heatstressed fattening pigs

As climate change intensifies, heat stress mitigation for pigs becomes more important. Trials involving induced heat waves are useful to test several measures (e.g. reduced stocking density) at a faster rate, but only when accurately evaluated and validated. In the present study, we investigated the suitability of an artificial heating protocol at different pig weights (experiment 1). The impact of different stocking densities on fattening pigs during an artificial heat wave (experiment 2) was also investigated. Experiment 1: Forty 20-week-old pigs weighing 96.5 ± 7.3 kg (W100) and forty 17-week-old pigs weighing 72.7 ± 9.9 kg (W70) were housed in two compartments. An artificial heat wave (heat load) was induced for 3 days. During 3-day periods before, during and after the heat load, physiological parameters (respiration rate (RR), rectal temperature (Trectal), skin temperature (Tskin) and behavior) were measured and average daily feed intake was observed. Ambient temperature, relative humidity and temperature-humidity index (THI) were monitored. Experiment 2: A total of 150 fattening pigs were randomly divided into three treatment groups: SD1.3 (1.3 m2/pig), SD1.0 (1.0 m2/pig) and SD0.8 (0.8 m2/pig). All pens had a total pen surface of 4.88 m2, corresponding with 4, 5 and 6 fattening pigs in the SD1.3, SD1.0 and SD0.8 groups, respectively. The heat load was induced for 7 days on week 21. Respiration rate and Trectal were observed as in experiment 1. Average daily gain and average daily feed intake were also noted. During the heat load, THI reached ≥ 75 (78.4 (experiment 1) and 78.6 (experiment 2)), even when relative humidity decreased to ± 45%. Every physiological parameter showed significant increases during the heat load. The prolonged heating protocol in experiment 2 also provoked significant decreases in average daily feed intake (15%) and average daily gain (19%) for all groups. Weight within the studied range of 70-100 kg did not have a significant impact on any of the parameters. However, Tskin was affected by both weight and heat load (P < 0.05), where Tskin from W100 was always lower in comparison to W70. In addition, we found that 0.8 m2/pig doubled the increase of Trectal during the heat load, namely SD0.8 (0.22 °C) compared to SD1.0 (0.12 °C) (P = 0.033) and SD1.3 (0.13 °C) (P = 0.053). This suggests that pigs housed at higher densities are less able to regulate their internal heat production. However, RR and performances were not significantly affected by heat load in this experimental set-up. A stocking density of 1.0 m2/animal may be sufficient to mitigate some negative effects of heat stress.

Estimation of Heat Production Rate using Thermal Data During Exercise in Indoor Environments: A Study of Heat Storage Rate in Male Athletes

The increasing preference for indoor exercise spaces highlights the relationship between indoor thermal environments and physiological responses, particularly concerning thermal comfort during physical activity. Determining the metabolic heat production rate during exercise is essential for optimizing the thermal comfort, well-being, and performance of individuals engaged in physical activities. This value can be determined during the activity using several methods, including direct calorimetry measurement, indirect calorimetry that uses analysis of respiratory gases, or approximations using collected data such as speed, body mass, and heart rate. The study aimed to calculate the metabolic heat production rate by infrared thermal evaluation (ITE) based on the body's thermal balance approach and compare it with the values determined by indirect calorimetry (IC). Fourteen participants volunteered for the study, using a cycling ergometer in a controlled climatic chamber. After the familiarization sessions, maximal O2 intake levels (VO2max) were determined through maximal graded exercise tests. Subsequently, constant work rate exercise tests were performed at 60% of VO2max for 20 min. The metabolic heat production rates were calculated by IC and ITE for each athlete individually. Respiratory gases were used to determine IC, while body skin and core temperatures, along with physical environmental data, were applied to calculate ITE using the human body thermal balance approximation of ASHRAE. According to the results, heat storage rates were misleading among the body's heat transfer modes, particularly during the first 8 min of the exercise. ITE showed a moderate level of correlation with IC (r: 0.03-0.86) with a higher level of dispersion relative to the mean (CV%: 12-84%). Therefore, a new equation (ITEnew) for the heat storage rates was proposed using the experimental data from this study. The results showed that ITEnew provided more precise estimations for the entire exercise period (p > 0.05). Correlations between ITEnew and IC values were consistently strong throughout the exercise period (r: 0.62-0.85). It can be suggested that ITEnew values can predict IC during the constant work rate steady-state exercise.

Exercise-induced changes in lower limbs skin temperature against plasma ATP among individuals with various type and level of physical activity

The objective of the study was to examine the lower limbs skin temperature (TSK) changes in response to exhaustive whole-body exercise in trained individuals in reference to changes in plasma adenosine triphosphate (ATP). Eighteen trained participants from distinct sport type ‒ endurance (25.2 ± 4.9 yr) and speed-power (25.8 ± 3.1 yr), and 9 controls (24,9 ± 4,3 yr) ‒ were examined. Lower limbs TSK and plasma ATP measures were applied in parallel in response to incremental treadmill test and during 30-min recovery period. Plasma ATP kinetics were inversely associated to changes in TSK. The first significant decrease in TSK (76-89% of V˙ O2MAX) occurred shortly before a significant plasma ATP increase (86-97% of V˙ O2MAX). During recovery, TSK increased, reaching pre-exercise values (before exercise vs. after 30-min recovery: 31.6 ± 0.4 °C vs. 32.0 ± 0.8 °C, p = 0.855 in endurance; 32.4 ± 0.5 °C vs. 32.9 ± 0.5 °C, p = 0.061 in speed-power; 31.9 ± 0.7 °C vs. 32.4 ± 0.8 °C, p = 0.222 in controls). Plasma ATP concentration did not returned to pre-exercise values in well trained participants (before exercise vs. after 30-min recovery: 699 ± 57 nmol l-1 vs. 854 ± 31 nmol l-1, p < 0.001, η2 = 0.961 and 812 ± 35 nmol l-1 vs. 975 ± 55 nmol l-1, p < 0.001, η2 = 0.974 in endurance and speed-power, respectively), unlike in controls (651 ± 40 nmol l-1 vs. 687 ± 61 nmol·l-1, p = 0.58, η2 = 0.918). The magnitude of TSK and plasma ATP response differed between the groups (p < 0.001, η2 = 0.410 for TSK; p < 0.001, η2 = 0.833 for plasma ATP). We conclude that lower limbs TSK change indirectly corresponds to the reverse course of plasma ATP during incremental exercise and the magnitude of the response depends on the level of physical activity and the associated to it long-term metabolic adaptation.

[Selected aspects regarding social factors in skin diseases]

Skin diseases are complex and cannot be explained solely by genetic or environmental factors but are also significantly shaped by social influences. This review illuminates the bidirectional relationship between social factors and skin diseases, demonstrating how social determinants such as socioeconomic status, living environment, and psychosocial stress can influence the onset and progression of skin conditions. Simultaneously, it explores how skin diseases can affect individuals' social lives and work capability, leading to a cycle of social withdrawal and further deterioration of the condition. The paper describes the need for a holistic approach in dermatology that goes beyond the biomedical perspective and incorporates social factors to develop effective prevention and treatment strategies. The increasing prevalence of skin diseases in Europe and the expected rise in allergies due to climate change make the consideration of social determinants even more urgent. The findings of this review aim to raise awareness of the complex interconnections between social factors and skin health and contribute to reducing social disparities in skin health.

The Potential of Exercise on Lifestyle and Skin Function: Narrative Review

BACKGROUND

The skin is an important organ of the human body and has moisturizing and barrier functions. Factors such as sunlight and lifestyle significantly affect these skin functions, with sunlight being extremely damaging. The effects of lifestyle habits such as smoking, diet, and sleep have been studied extensively. It has been found that smoking increases the risk of wrinkles, while excessive fat and sugar intake leads to skin aging. Lack of sleep and stress are also dangerous for the skin's barrier function. In recent years, the impact of exercise habits on skin function has been a focus of study. Regular exercise is associated with increased blood flow to the skin, elevated skin temperature, and improved skin moisture. Furthermore, it has been shown to improve skin structure and rejuvenate its appearance, possibly through promoting mitochondrial biosynthesis and affecting hormone secretion. Further research is needed to understand the effects of different amounts and content of exercise on the skin.

OBJECTIVE

This study aims to briefly summarize the relationship between lifestyle and skin function and the mechanisms that have been elucidated so far and introduce the expected effects of exercise on skin function.

METHODS

We conducted a review of the literature using PubMed and Google Scholar repositories for relevant literature published between 2000 and 2022 with the following keywords: exercise, skin, and life habits.

RESULTS

Exercise augments the total spectrum power density of cutaneous blood perfusion by a factor of approximately 8, and vasodilation demonstrates an enhancement of approximately 1.5-fold. Regular exercise can also mitigate age-related skin changes by promoting mitochondrial biosynthesis. However, not all exercise impacts are positive; for instance, swimming in chlorinated pools may harm the skin barrier function. Hence, the exercise environment should be considered for its potential effects on the skin.

CONCLUSIONS

This review demonstrates that exercise can potentially enhance skin function retention.

Effects of physical training on hypothalamic neuronal activation and expressions of vasopressin and oxytocin in SHR after running until fatigue

To assess the influence of physical training on neuronal activation and hypothalamic expression of vasopressin and oxytocin in spontaneously hypertensive rats (SHR), untrained and trained normotensive rats and SHR were submitted to running until fatigue while internal body and tail temperatures were recorded. Hypothalamic c-Fos expression was evaluated in thermoregulatory centers such as the median preoptic nucleus (MnPO), medial preoptic nucleus (mPOA), paraventricular nucleus of the hypothalamus (PVN), and supraoptic nucleus (SON). The PVN and the SON were also investigated for vasopressin and oxytocin expressions. Although exercise training improved the workload performed by the animals, it was reduced in SHR and followed by increased internal body temperature due to tail vasodilation deficit. Physical training enhanced c-Fos expression in the MnPO, mPOA, and PVN of both strains, and these responses were attenuated in SHR. Vasopressin immunoreactivity in the PVN was also increased by physical training to a lesser extent in SHR. The already-reduced oxytocin expression in the PVN of SHR was increased in response to physical training. Within the SON, neuronal activation and the expressions of vasopressin and oxytocin were reduced by hypertension and unaffected by physical training. The data indicate that physical training counterbalances in part the negative effect of hypertension on hypothalamic neuronal activation elicited by exercise, as well as on the expression of vasopressin and oxytocin. These hypertension features seem to negatively influence the workload performed by SHR due to the hyperthermia derived from the inability of physical training to improve heat dissipation through skin vasodilation.

A randomized Phase I pre-operative window trial of transdermal endoxifen in women planning mastectomy: Evaluation of dermal safety, intra-mammary drug distribution, and biologic effects

Breast cancer prevention only requires local exposure of the breast to active drug. However, oral preventive agents entail systemic exposure, causing adverse effects that limit acceptance by high-risk women. Drug-delivery through the breast skin is an attractive option, but requires demonstration of dermal safety and drug distribution throughout the breast. We formulated the tamoxifen metabolite (E/Z)-endoxifen for transdermal delivery and tested it in a placebo-controlled, double-blinded Phase I trial with dose escalation from 10 to 20 mg daily. The primary endpoint was dermal toxicity. Thirty-two women planning mastectomy were randomized (2:1) to endoxifen-gel or placebo-gel applied to both breasts for 3-5 weeks. Both doses of endoxifen-gel incurred no dermal or systemic toxicity compared to placebo. All endoxifen-treated breasts contained the drug at each of five sampling locations; the median per-person tissue concentration in the treated participants was 0.6 ng/g (IQR 0.4-1.6), significantly higher (p < 0.001) than the median plasma concentration (0.2 ng/mL, IQR 0.2-0.2). The median ratio of the more potent (Z)-isomer to (E)-isomer at each breast location was 1.50 (IQR 0.96-2.54, p < 0.05). No discernible effects of breast size or adiposity on tissue concentrations were observed. At the endoxifen doses and duration used, and the tissue concentration achieved, we observed a non-significant overall reduction of tumor proliferation (Ki67 LI) and significant downregulation of gene signatures known to promote cancer invasion (FN1, SERPINH1, PLOD2, PDGFA, ITGAV) (p = 0.03). Transdermal endoxifen is an important potential breast cancer prevention agent but formulations with better dermal penetration are needed.

Regular exercise delays microvascular endothelial dysfunction by regulating antioxidant capacity and cellular metabolism

Aging is the basis for several unfavorable conditions, including cardiovascular diseases (CVDs). In this sense, regular physical activity (regular PA) has been proven to delay cellular aging and prevent endothelial dysfunction related to CVDs. Despite numerous studies involving athletes, little is known about cellular and molecular mechanisms of regular PA among master athletes. The present study aimed at evaluating the effects of regular PA on local microcirculatory functions in elderly athletes as compared to age-matched sedentary controls. Moreover, molecular/epigenetic mechanisms (nitric oxide, oxidative stress, PGC-1α, SIRT1 and miR29) were also assessed. The results of the present study showed that regular PA significantly increased local blood flow in post-ischemia and post-heating conditions, as well as NO plasma concentrations, denoting a better endothelial function/microcirculatory efficiency. Moreover, athletes presented a greater plasma antioxidant and increased transcriptional levels of the metabolism regulator PGC-1α. Finally, regular PA enhanced plasma level of SIRT1 and miR29, suggested as epigenetic regulators of redox balance and cellular metabolism. In addition, stimulated local blood flow was directly related to plasma antioxidant capacity, and SIRT1 and miR29 levels. Overall, our data confirm the beneficial effects of regular PA on the cardiovascular profile in elderly athletes and shed light on molecular signals involved in the positive adaptations to exercise.

Workload and sex effects in comprehensive assessment of cutaneous microcirculation

INTRODUCTION

Workload and sex-related differences have been proposed as factors of importance when evaluating the microcirculation. Simultaneous assessments with diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF) enable a comprehensive evaluation of the microcirculation. The aim of the study was to compare the response between sexes in the microcirculatory parameters red blood cell (RBC) tissue fraction, RBC oxygen saturation, average vessel diameter, and speed-resolved perfusion during baseline, cycling, and recovery, respectively.

METHODS

In 24 healthy participants (aged 20 to 30 years, 12 females), cutaneous microcirculation was assessed by LDF and DRS at baseline, during a workload generated by cycling at 75 to 80 % of maximal age-predicted heart rate, and recovery, respectively.

RESULTS

Females had significantly lower RBC tissue fraction and total perfusion in forearm skin microcirculation at all phases (baseline, workload, and recovery). All microvascular parameters increased significantly during cycling, most evident in RBC oxygen saturation (34 % increase on average) and perfusion (9-fold increase in total perfusion). For perfusion, the highest speeds (>10 mm/s) increased by a factor of 31, whereas the lowest speeds (<1 mm/s) increased by a factor of 2.

CONCLUSION

Compared to a resting state, all studied microcirculation measures increased during cycling. For perfusion, this was mainly due to increased speed, and only to a minor extent due to increased RBC tissue fraction. Skin microcirculatory differences between sexes were seen in RBC concentration and total perfusion.

The peripheral vascular responses in non-freezing cold injury and matched controls

NEW FINDINGS

What is the central question of this study? Does non-freezing cold injury (NFCI) alter normal peripheral vascular function? What is the main finding and its importance? Individuals with NFCI were more cold sensitive (rewarmed more slowly and felt more discomfort) than controls. Vascular tests indicated that extremity endothelial function was preserved with NFCI and that sympathetic vasoconstrictor response might be reduced. The pathophysiology underpinning the cold sensitivity associated with NFCI thus remains to be identified.

ABSTRACT

The impact of non-freezing cold injury (NFCI) on peripheral vascular function was investigated. Individuals with NFCI (NFCI group) and closely matched controls with either similar (COLD group) or limited (CON group) previous cold exposure were compared (n = 16). Peripheral cutaneous vascular responses to deep inspiration (DI), occlusion (PORH), local cutaneous heating (LH) and iontophoresis of acetylcholine and sodium nitroprusside were investigated. The responses to a cold sensitivity test (CST) involving immersion of a foot in 15°C water for 2 min followed by spontaneous rewarming, and a foot cooling protocol (footplate cooled from 34°C to 15°C), were also examined. The vasoconstrictor response to DI was lower in NFCI compared to CON (toe: 73 (28)% vs. 91 (17)%; P = 0.003). The responses to PORH, LH and iontophoresis were not reduced compared to either COLD or CON. During the CST, toe skin temperature rewarmed more slowly in NFCI than COLD or CON (10 min: 27.4 (2.3)°C vs. 30.7 (3.7)°C and 31.7 (3.9)°C, P < 0.05, respectively); however, no differences were observed during the footplate cooling. NFCI were more cold-intolerant (P < 0.0001) and reported colder and more uncomfortable feet during the CST and footplate cooling than COLD and CON (P < 0.05). NFCI showed a decreased sensitivity to sympathetic vasoconstrictor activation than CON and greater cold sensitivity (CST) compared to COLD and CON. None of the other vascular function tests indicated endothelial dysfunction. However, NFCI perceived their extremities to be colder and more uncomfortable/painful than the controls.

Acute impact of aerobic exercise on local cutaneous thermal hyperaemia

Little is known about the acute changes in cutaneous microvascular function that occur in response to exercise, the accumulation of which may provide the basis for beneficial chronic cutaneous vascular adaptations. Therefore, we examined the effects of acute exercise on cutaneous thermal hyperaemia. Twelve healthy, recreationally active participants (11 male, 1 female) performed 30-minute cycling at 50 % (low-intensity exercise, LOW) or 75 % (high-intensity exercise, HIGH) maximum heart rate. Laser Doppler flowmetry (LDF) and rapid local skin heating were used to quantify cutaneous thermal hyperaemia before (PRE), immediately following (IMM) and 1-h (1HR) after exercise. Baseline, axon reflex peak, axon reflex nadir, plateau, maximum skin blood flow responses to rapid local heating (42 °C for 30-min followed by 44 °C for 15-min) at each stage were assessed and indexed as cutaneous vascular conductance [CVC = flux / mean arterial blood pressure (MAP), PU·mm Hg^-1], and expressed as a percentage of maximum (%CVC_max). Exercise increased heart rate (HR), MAP and skin blood flow (all P < 0.001), and to a greater extent during HIGH (all P < 0.001). The axon reflex peak and nadir were increased immediately and 1-h after exercise (all comparisons P < 0.01 vs. PRE), which did not differ between intensities (peak: P = 0.34, axon reflex nadir: P = 0.91). The endothelium-dependent plateau response was slightly elevated after exercise (P = 0.06), with no effect of intensity (P = 0.58) nor any interaction effect (P = 0.55). CONCLUSION: Exercise increases cutaneous microvascular axonal responses to local heating for up to 1-h, suggesting an augmented sensory afferent function post-exercise. Acute exercise may only modestly affect endothelial function in cutaneous microcirculation.

Physical activity and exercise for hot flashes: trigger or treatment?

IMPORTANCE AND OBJECTIVE

Hot flashes (HFs) are a prevalent feature of menopause. Hot flashes can be bothersome and affect quality of life. However, HFs have also been associated with the risk for cardiovascular disease. Therefore, providing current evidence on the effect of therapies to reduce HFs can help patients and providers with decision making. This review provides details on the scientific evidence to date related to the effect of physical activity (PA) and exercise to alter the HF experience in women.

METHODS

The PubMed database was searched between June 2020 and June 2022 for currently available evidence regarding the relation between PA and exercise and HFs. Our analysis included randomized control trials on exercise training, epidemiological studies, and studies evaluating acute exercise on the self-reported and objectively measured HF experience in addition to systematic reviews on the topic published as of June 2022.

DISCUSSION AND CONCLUSIONS

The majority of evidence from randomized control trials indicates that aerobic and resistance exercise training lead to a decrease in subjectively experienced HFs. The limited available studies on acute exercise indicate that a bout of moderate-intensity exercise may decrease objectively measured and self-reported HFs but acute increases in PA intensity above accustomed levels may influence subjective HF experience. Some evidence suggests that for those with depression, habitual PA may be an effective way to reduce HF symptoms. Weighing the available evidence, for people who experience HFs, engaging in regular moderate-intensity PA, including aerobic and resistance exercise, may be an effective therapy to reduce HFs and women should be counseled on the benefits of regular, moderate exercise. However, significant gaps in knowledge remain about the optimal exercise prescription, effectiveness for a diverse population, meaning of differences between objective and subjective experience, and mechanisms that lead to changes in HFs.

Effects of the Whole-Body Vibration Exercise on Sleep Disorders, Body Temperature, Body Composition, Tone, and Clinical Parameters in a Child with Down Syndrome Who Underwent Total Atrioventricular Septal Defect Surgery: A Case-Report

BACKGROUND

The health and developmental issues of people with Down syndrome (DS) are complex and are associated with many medical, psychological, and social problems from childhood through into adulthood. DS children have an increased risk of multiorgan comorbidities, including congenital heart disease. Atrioventricular septal defect (AVSD) is a congenital heart malformation that often occurs in DS people.

AIM

Physical activity and exercise are recommended for patients with cardiovascular disease and are considered to be the gold standard of cardiac rehabilitation. Whole-body vibration exercise (WBVE) is considered a form of exercises. The aim of this case report is to show the effects of WBVE on sleep disturbances, body temperature, body composition, tone, and clinical parameters in a child with DS with corrected total AVSD. The subject is a 10-year-old girl, with free-type DS, who underwent surgery to correct a total AVSD at 6 months. She underwent periodic cardiological monitoring and was released to perform any type of physical exercise, including WBVE. WBVE improved sleep quality and body composition.

CONCLUSION

WBVE leads to physiological effects that benefit the DS child.

The use of thermal imaging for monitoring the training progress of professional male sweep rowers

This study assesses the thermal profile of the skin in highly trained rowers and investigates the relationship between resting skin temperature (Ts) and the muscle peak torque (PT) measured in statics at the beginning (autumn) and the end (spring) of the preparatory period. Ten professional male sweep rowers, members of the Polish national rowing team, were investigated. A thermal imaging camera was used to analyze the Ts. The PT of the muscles involved in the rowing cycle were measured isometrically. No significant temperature asymmetries were found, except in front of arms after exercise in the spring (p = 0.0228). In contrast, the PT test in the autumn confirmed the significant asymmetry of the knee joint extensors (p = 0.0192). In spring compared to autumn, Ts in many areas of the body were slightly higher, as was PT of underlying muscles. Significant correlations between resting Ts and PT of the underlying muscles were found. Thermal imaging makes it possible to observe changes in skin temperature and symmetry before and after exercise. At this stage, it does not appear to be a method that, without supporting of other methods such as those assessing muscle function, will allow monitoring of training progress.

Human temperature regulation under heat stress in health, disease, and injury

The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.

Visualising and quantifying microvascular structure and function in patients with heart failure using optical coherence tomography

Abstract

Key points

Reactive hyperemia augments local heat-induced skin hyperemia

NEW FINDINGS

What is the central question of this study? It is valuable to be able to monitor disease or treatment related changes in the microcirculation. Laser doppler flowmetry with local heating allows noninvasive monitoring of the skin microcirculation and its ability to vasodilate. Does reactive hyperemia augment the increase in skin blood flow elicited by local heating? What is the main finding and its importance? The results of this study show that the addition of reactive hyperemia to local heating results in greater vasodilation than heating alone. Thus, reactive hyperemia can augment local heat-induced hyperemia in the skin.

ABSTRACT

The skin circulation has been proposed as a model of generalized microvascular function which could be monitored noninvasively using laser doppler flowmetry (LDF). The response to heat hyperemia (HH) is commonly used to monitor disease or treatment related changes in microvascular function. We hypothesized that reactive hyperemia would augment the increase in skin blood flow elicited by local heating. Fourteen healthy young adults were subjected to 3 different conditions: reactive hyperemia (RH; skin temperature controlled at 33°C), heat hyperemia (HH; 42°C held for 40 minutes), and HH+RH. Two Peltier-controlled thermomodules with laser LDF probes were placed on the right forearm to continuously monitor skin blood flow. A cuff was placed on the right upper arm to elicit RH by inflation to 220 mmHg for 5 minutes. This procedure was performed with skin temperature at 33°C and again after 40 min of local heating to 42°C. Beat-by-beat mean arterial pressure (MAP) obtained by a photoplethysmographic sensor on the middle finger of the left hand allowed calculation of cutaneous vascular conductance (CVC) as LDF / MAP. Both HH and RH increased LDF (p<0.0001 and p <0.0001, respectively) and CVC (p = 0.0001 and p<0.0001) above baseline values. LDF and CVC values were significantly higher during HH+RH when compared to RH or HH alone (p<0.0001). In summary, HH+RH resulted in greater vasodilation when compared to HH or RH alone. These results indicate that RH can augment local heat-induced hyperemia in the skin. This article is protected by copyright. All rights reserved.

Correlates of Calcidiol Deficiency in Adults-Cross-Sectional, Observational, Population-Based Study

The prevalence, determinants, and clinical significance of vitamin D deficiency in the population are debated. The population-based study investigated the cross-sectional associations of several variables with serum 25-hydroxyvitamin D (calcidiol) measured using standardized calibrators. The study cohort consisted of 979 persons of the Moli-sani study, both sexes, ages ≥35 years. The correlates in the analyses were sex, age, education, local solar irradiance in the month preceding the visit, physical activity, anthropometry, diabetes, kidney function, albuminuria, blood pressure, serum cholesterol, smoking, alcohol intake, calorie intake, dietary vitamin D intake, and vitamin D supplement. The serum calcidiol was log transformed for linear regression because it was positively skewed (skewness = 1.16). The prevalence of calcidiol deficiency defined as serum calcidiol ≤12 ng/mL was 24.5%. In multi-variable regression, older age, lower solar irradiance, lower leisure physical activity, higher waist/hip ratio, higher systolic pressure, higher serum cholesterol, smoking, lower alcohol intake, and no vitamin D supplement were independent correlates of lower serum calcidiol (95% confidence interval of standardized regression coefficient ≠ 0) and of calcidiol deficiency (95% confidence interval of odds ratio > 1). The data indicate that low serum calcidiol in the population could reflect not only sun exposure, age, and vitamin D supplementation but also leisure physical activity, abdominal obesity, systolic hypertension, hypercholesterolemia, smoking, and alcohol intake.

Influence of Soldiers' Cardiorespiratory Fitness on Physiological Responses and Dropouts During a Loaded Long-distance March

INTRODUCTION

In military service, marching is an important, common, and physically demanding task. Minimizing dropouts, maintaining operational readiness during the march, and achieving a fast recovery are desirable because the soldiers have to be ready for duty, sometimes shortly after an exhausting task. The present field study investigated the influence of the soldiers' cardiorespiratory fitness on physiological responses during a long-lasting and challenging 34 km march.

MATERIALS AND METHODS

Heart rate (HR), body core temperature (BCT), total energy expenditure (TEE), energy intake, motivation, and pain sensation were investigated in 44 soldiers (20.3 ± 1.3 years, 178.5 ± 7.0 cm, 74.8 ± 9.8 kg, body mass index: 23.4 ± 2.7 kg × m-2, peak oxygen uptake ($\dot{\rm{V}}$O2peak): 54.2 ± 7.9 mL × kg-1 × min-1) during almost 8 hours of marching. All soldiers were equipped with a portable electrocardiogram to record HR and an accelerometer on the hip, all swallowed a telemetry pill to record BCT, and all filled out a pre- and post-march questionnaire. The influence of aerobic capacity on the physiological responses during the march was examined by dividing the soldiers into three fitness groups according to their $\dot{\rm{V}}$O2peak.

RESULTS

The group with the lowest aerobic capacity ($\dot{\rm{V}}$O2peak: 44.9 ± 4.8 mL × kg-1 × min-1) compared to the group with the highest aerobic capacity ($\dot{\rm{V}}$O2peak: 61.7 ± 2.2 mL × kg-1 × min-1) showed a significantly higher (P < .05) mean HR (133 ± 9 bpm and 125 ± 8 bpm, respectively) as well as peak BCT (38.6 ± 0.3 and 38.4 ± 0.2 °C, respectively) during the march. In terms of recovery ability during the break, no significant differences could be identified between the three groups in either HR or BCT. The energy deficit during the march was remarkably high, as the soldiers could only replace 22%, 26%, and 36% of the total energy expenditure in the lower, middle, and higher fitness group, respectively. The cardiorespiratory fittest soldiers showed a significantly higher motivation to perform when compared to the least cardiorespiratory fit soldiers (P = .002; scale from 1 [not at all] to 10 [extremely]; scale difference of 2.3). A total of nine soldiers (16%) had to end marching early: four soldiers (21%) in the group with the lowest aerobic capacity, five (28%) in the middle group, and none in the highest group.

CONCLUSION

Soldiers with a high $\dot{\rm{V}}$O2peak showed a lower mean HR and peak BCT throughout the long-distance march, as well as higher performance motivation, no dropouts, and lower energy deficit. All soldiers showed an enormous energy deficit; therefore, corresponding nutritional strategies are recommended.

Effect of fatigue strength exercise on anterior thigh skin temperature rewarming after cold stress test

Although dynamic thermography skin temperature assessment has been used in medical field, scientific evidence in sports is scarce. The aim of the study was to assess changes in anterior thigh skin temperature in response to a cold stress test after a strength exercise fatiguing protocol. Ten physically active adults performed a familiarization session and two strength exercise sessions, one with dominant and the other with non-dominant lower limb. Participants performed bouts of 10 concentric and eccentric contractions of leg extensions in an isokinetic device until reaching around 30% of force loss. Infrared thermographic images were taken at baseline conditions and after the fatigue level from both thighs after being cooled using a cryotherapy system. ROIs included vastus medialis, rectus femoris, adductor and vastus lateralis. Skin temperature rewarming was assessed during 180s after the cooling process obtaining the coefficients of the following equation: ΔSkin temperature = β₀ + β_{1 *} ln(T), being β₀ and β₁ the constant and slope coefficients, respectively, T the time elapsed following the cold stress in seconds, and ΔSkin temperature the difference between the skin temperature at T respect and the pre-cooling moment. Lower β₀ and higher β₁ were found for vastus lateralis and rectus femoris in the intervention lower limb compared with baseline conditions (p < 0.05 and ES > 0.6). Adductor only showed differences in β₀ (p = 0.01 and ES = 0.92). The regressions models obtained showed that β₀ and β₁ had a direct relationship with age and muscle mass, but an inverse relationship with the number of series performed until 30% of fatigue (R² = 0.8). In conclusion, fatigue strength exercise results in a lower skin temperature and a faster thermal increase after a cold stress test.

Adaptation to Exercise Training in Conduit Arteries and Cutaneous Microvessels in Humans: An Optical Coherence Tomography Study

INTRODUCTION

Exercise training has antiatherogenic effects on conduit and resistance artery function and structure in humans and induces angiogenic changes in skeletal muscle. However, training-induced adaptation in cutaneous microvessels is poorly understood, partly because of technological limitations. Optical coherence tomography (OCT) is a novel high-resolution imaging technique capable of visualizing cutaneous microvasculature at a resolution of ~30 μm. We utilized OCT to visualize the effects of training on cutaneous microvessels, alongside assessment of conduit artery flow-mediated dilation (FMD).

METHODS

We assessed brachial FMD and cutaneous microcirculatory responses at rest and in response to local heating and reactive hyperemia: pretraining and posttraining in eight healthy men compared with age-matched untrained controls (n = 8). Participants in the training group underwent supervised cycling at 80% maximal heart rate three times a week for 8 wk.

RESULTS

We found a significant interaction (P = 0.04) whereby an increase in FMD was observed after training (post 9.83% ± 3.27% vs pre 6.97% ± 1.77%, P = 0.01), with this posttraining value higher compared with the control group (6.9% ± 2.87%, P = 0.027). FMD was not altered in the controls (P = 0.894). There was a significant interaction for OCT-derived speed (P = 0.038) whereby a significant decrease in the local disk heating response was observed after training (post 98.6 ± 3.9 μm·s-1 vs pre 102 ± 5 μm·s-1, P = 0.012), whereas no changes were observed for OCT-derived speed in the control group (P = 0.877). Other OCT responses (diameter, flow rate, and density) to local heating and reactive hyperemia were unaffected by training.

CONCLUSIONS

Our findings suggest that vascular adaptation to exercise training is not uniform across all levels of the arterial tree; although exercise training improves larger artery function, this was not accompanied by unequivocal evidence for cutaneous microvascular adaptation in young healthy subjects.

Monitoring adaptation of skin tissue oxygenation during cycling ergometer exercise by frequency-domain diffuse optical spectroscopy

In addition to supplying oxygen molecule O2 for metabolic functions during the adaptation to exercise, blood also plays a critical role in heat dissipation for core temperature stabilization. This study investigates the status of hemodynamic oxygenation in the forearm's skin tissue of three participants during a complete ergometer exercise from the resting to exercising, and to recovering conditions using a three-wavelength frequency-domain diffuse reflectance spectroscopy (FD DRS) alongside the monitoring of heartbeat rate and skin temperature. The FD DRS system was synchronized with radiofrequency (RF)-modulated input photon sources and the respective output to extract time-course absorption and scattering coefficients of the skin tissue, which, through the fitting of lambert's law of absorbance, can be used to determine the concentration of oxygenated/deoxygenated hemoglobin molecules, and consequentially, the oxygen saturation of skin tissue and total hemoglobin (THb) concentration. Expressly, a sudden jump in heartbeat rate at the beginning of the exercise, a temporal lag of the rising edge of skin temperature behind that of the THb concentration in the procession of step-wise incremental working intensity, and the uprising of THb in the exhaustion zone in responses to the physiological adaptation to exercise were identified. Finally, conclusive remarks were drawn that the FD DRS system is useful in extracting the hemodynamic properties of forearm skin which is often being neglected in previous exercise physiology studies by DRS-related techniques. The detailed variation of hemodynamic and optical scattering parameters of forearm skin elucidated in the studies can be applied for the analysis of athletes' physiological status, and may be a potential reference for the design of future wearable devices.

Relationship between Skin Temperature Variation and Muscle Damage Markers after a Marathon Performed in a Hot Environmental Condition

This study aimed to assess the effect of a marathon running at a hot environmental temperature on the baseline skin temperature (Tsk) of the posterior day and to analyze the relationship between Tsk response and muscle damage markers variation. The Tsk, creatine kinase, and lactate dehydrogenase of 16 marathon runners were assessed four times before (15 days and 45 min) and after (24 h and 6 days) a marathon in a hot environment (thermal stress index = 28.3 ± 3.3 °C and humidity ~81%). The Tsk of thirteen different body regions of both right and left lower limbs were analyzed. Higher values after the marathon were observed than 45 min before in creatine kinase (174.3 ± 136.4 UI/L < 1159.7 ± 699.7 UI/L, p < 0.01 and large effect size) and lactate dehydrogenase (362.6 ± 99.9 UI/L < 438 ± 115.5 UI/L, p = 0.02 and moderate effect size). Generally, Tsk was higher the day after the marathon than at the other three moments (e.g., rectus femoris region, 6 days before vs. the day after, 95% confidence interval of the difference (0.3, 1.6 °C), p = 0.04 and large effect size). No relationship or correlation was observed between the variation of Tsk and muscle damage markers (p > 0.05). In conclusion, performing a marathon in a hot environmental condition results in a higher Tsk the day after the marathon. This increase in Tsk could be because of the heat generated by the marathon and its subsequent physiological processes (e.g., increase in endothelial nitric oxide, glycogen resynthesis, or increase of systemic hormones), which would be reflected in the Tsk due to the peripheral vasodilation promoted by the hot environment. However, among these processes, muscle damage does not seem to be of great importance due to the lack of an observed relationship between Tsk and muscle damage markers.

Blood pressure variability and microvascular dysfunction: the Maastricht Study

BACKGROUND

Microvascular dysfunction (MVD) contributes to stroke, dementia, depression, retinopathy and chronic kidney disease. However, the determinants of MVD are incompletely understood. Greater blood pressure variability (BPV) may be one such determinant.

METHODS AND RESULTS

We used cross-sectional data of The Maastricht Study (n = 2773, age 59.9 years; 51.9% men) to investigate whether greater very short- to mid-term BPV is associated with various MVD measures. We standardized and averaged within-visit, 24-h and 7-day BPV into a systolic and a diastolic BPV composite score. MVD measures included a composite score of MRI cerebral small vessel disease (CSVD) features (total brain parenchymal volume, white matter hyperintensity volume, lacunar infarcts and cerebral microbleeds), a composite score of flicker light-induced retinal arteriolar and venular dilation response, albuminuria, heat-induced skin hyperemia and a composite score of plasma biomarkers of MVD (sICAM-1, sVCAM-1, sE-selectin and von Willebrand Factor). We used linear regression adjusted for age, sex, glucose metabolism status, mean 24-h systolic or DBP, cardiovascular risk factors and antihypertensive medication. We found that higher systolic and diastolic BPV composite scores (per SD) were associated with higher albuminuria [higher ratio, 1.04 (95% CI 1.00-1.08) and 1.07 (1.03-1.11), respectively], but not with other measures of MVD tested.

CONCLUSION

Greater systolic and diastolic BPV was associated with higher albuminuria, but not with CSVD features, flicker light-induced retinal arteriolar and venular dilation response, heat-induced skin hyperemia and plasma biomarkers of MVD. This suggests that the microvasculature of the kidneys is most vulnerable to the detrimental effects of greater BPV.

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat by examining the benefits of heat acclimation, cooling strategies, and hyperhydration. Finally, contemporary controversies are summarized and future research directions are provided.

Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function

About 2% of the world’s population suffers from small nerve fiber dysfunction, neuropathy, which can result in severe pain. This condition is caused by damage to the small nerve fibers and its assessment is challenging, due to the lack of simple and objective diagnostic techniques. The present study aimed to develop a contactless photoplethysmography system using simple instrumentation, for objective and non-invasive assessment of small cutaneous sensory nerve fiber function. The approach is based on the use of contactless photoplethysmography for the characterization of skin flowmotions and topical heating evoked vasomotor responses. The feasibility of the technique was evaluated on volunteers (n = 14) using skin topical anesthesia, which is able to produce temporary alterations of cutaneous nerve fibers function. In the treated skin region in comparison to intact skin: neurogenic and endothelial component of flowmotions decreased by ~61% and 41%, the local heating evoked flare area decreased by ~44%, vasomotor response trend peak and nadir were substantially reduced. The results indicate for the potential of the remote photoplethysmography in the assessment of the cutaneous nerve fiber function. It is believed that in the future this technique could be used in the clinics as an affordable alternative to laser Doppler imaging technique.

Exercise training improves microvascular function in patients with Chagas heart disease: Data from the PEACH study

BACKGROUND

Chagas heart disease (CHD) impairs the systemic microvascular function. We investigated the effects of exercise training on cutaneous microvascular function among patients with CHD.

METHODS

Patients from the PEACH study were randomly assigned to a supervised exercise training 3 times/week for 6 months (Trained; n = 10) or a control group (Untrained; n = 8). Both groups underwent evaluation of microvascular function before, and at 3- and 6-months of follow-up. Cutaneous vascular conductance (CVC) was assessed in the skin of the forearm using laser speckle contrast imaging coupled with iontophoresis of acetylcholine (ACh), sodium nitroprusside (SNP) and during post-occlusive reactive hyperemia (PORH).

RESULTS

At 3-months of follow-up, no difference was detected between groups in CVC responses to ACh (p = 0.50), SNP (p = 0.26) and HRPO (p = 0.65). However, at 6-months of follow-up, trained vs. untrained patients improved CVC induced by SNP-iontophoresis (0.19 ± 0.10 vs. 0.14 ± 0.15 APU.mmHg^-1; p = 0.05) and PORH (0.63 ± 0.15 vs. 0.48 ± 0.18 APU.mmHg^-1; p = 0.05). CVC response to ACh-iontophoresis was similar between groups (0.19 ± 0.11 vs. 0.22 ± 0.17 APU.mmHg^-1; p = 0.38).

CONCLUSION

Exercise training performed during 6 months improved the cutaneous microvascular function of CHD patients. Further studies evaluating the mechanism involved in this response are warranted.

The immediate effect of whole-body vibration on rectus abdominis muscle activity and cutaneous temperature: A randomized controlled trial

OBJECTIVES

To compare acute effects of isometric abdominal exercises performed with or without vibration on the electromyographic activity and cutaneous temperature in the abdominal region of physically active individuals.

METHODS

A randomized controlled crossover clinical trial was undertaken in thirty volunteers who completed one unique session of two different protocols of interventions apart from a week from each other, in a two-week study protocol. The subjects were randomly divided in to two groups of 15 volunteers; both were assigned to perform board exercise (30 s on the front, right and left lateral boards, with a rest interval of 2 min). The first group performed it on a vibrating platform at a frequency of 30 Hz for the first week, while the remaining participants executed the same exercise without stimulates vibration. In the second week the protocol was inverted. The outcome were surface electromyography (EMG) data for the rectus abdominis muscle (RAM) and cutaneous temperature (CT) of the abdominal region. Normality was accepted, and Student's t-tests were used to compare the measurements for dependents variables (P < 0.05).

RESULTS

There were no differences in RAM activation and CT between protocols with or without vibration (P > 0.05). CT increased (P = 0.001) after both the exercises with and without vibration.

CONCLUSION

The results suggest that there were no effects in cutaneous temperature or muscle activation through the use of vibration associated with isometric abdominal exercises.

Whole body passive heating versus dynamic lower body exercise: a comparison of peripheral hemodynamic profiles

Passive heating has emerged as a therapeutic intervention for the treatment and prevention of cardiovascular disease. Like exercise, heating increases peripheral artery blood flow and shear rate, which is thought to be a primary mechanism underpinning endothelium-mediated vascular adaptation. However, few studies have compared the increase in arterial blood flow and shear rate between dynamic exercise and passive heating. In a fixed crossover design study, 15 moderately trained healthy participants (25.6 ± 3.4 yr) (5 female) underwent 30 min of whole body passive heating (42°C bath), followed on a separate day by 30 min of semi-recumbent stepping exercise performed at two workloads corresponding to the increase in cardiac output (Qc) (Δ3.72 L·min^-1) and heart rate (HR) (Δ40 beats/min) recorded at the end of passive heating. At the same Qc (Δ3.72 L·min^-1 vs. 3.78 L·min^-1), femoral artery blood flow (1,599 mL/min vs. 1,947 mL/min) (P = 0.596) and shear rate (162 s^-1 vs. 192 s^-1) (P = 0.471) measured by ultrasonography were similar between passive heating and stepping exercise. However, for the same HR_MATCHED intensity, femoral blood flow (1,599 mL·min^-1 vs. 2,588 mL·min^-1) and shear rate (161 s^-1 vs. 271 s^-1) were significantly greater during exercise, compared with heating (both P = <0.001). The results indicate that, for moderately trained individuals, passive heating increases common femoral artery blood flow and shear rate similar to low-intensity continuous dynamic exercise (29% V̇o_2max); however, exercise performed at a higher intensity (53% V̇o_2max) results in significantly larger shear rates toward the active skeletal muscle.NEW & NOTEWORTHY Passive heating and exercise increase blood flow through arteries, generating a frictional force, termed shear rate, which is associated with positive vascular health. Few studies have compared the increase in arterial blood flow and shear rate elicited by passive heating with that elicited by dynamic continuous exercise. We found that 30 min of whole body passive hot-water immersion (42°C bath) increased femoral artery blood flow and shear rate equivalent to exercising at a moderate intensity (∼57% HR_max).

Predicting Transdermal Fentanyl Delivery Using Mechanistic Simulations for Tailored Therapy

Transdermal drug delivery is a key technology for administering drugs. However, most devices are “one-size-fits-all”, even though drug diffusion through the skin varies significantly from person-to-person. For next-generation devices, personalization for optimal drug release would benefit from an augmented insight into the drug release and percutaneous uptake kinetics. Our objective was to quantify the changes in transdermal fentanyl uptake with regards to the patient’s age and the anatomical location where the patch was placed. We also explored to which extent the drug flux from the patch could be altered by miniaturizing the contact surface area of the patch reservoir with the skin. To this end, we used validated mechanistic modeling of fentanyl diffusion, storage, and partitioning in the epidermis to quantify drug release from the patch and the uptake within the skin. A superior spatiotemporal resolution compared to experimental methods enabled in-silico identification of peak concentrations and fluxes, and the amount of stored drug and bioavailability. The patients’ drug uptake showed a 36% difference between different anatomical locations after 72 h, but there was a strong interpatient variability. With aging, the drug uptake from the transdermal patch became slower and less potent. A 70-year-old patient received 26% less drug over the 72-h application period, compared to an 18-year-old patient. Additionally, a novel concept of using micron-sized drug reservoirs was explored in silico. These reservoirs induced a much higher local flux (µg cm^-2 h^-1) than conventional patches. Up to a 200-fold increase in the drug flux was obtained from these small reservoirs. This effect was mainly caused by transverse diffusion in the stratum corneum, which is not relevant for much larger conventional patches. These micron-sized drug reservoirs open new ways to individualize reservoir design and thus transdermal therapy. Such computer-aided engineering tools also have great potential for in-silico design and precise control of drug delivery systems. Here, the validated mechanistic models can serve as a key building block for developing digital twins for transdermal drug delivery systems.

Relationship between Skin Temperature, Electrical Manifestations of Muscle Fatigue, and Exercise-Induced Delayed Onset Muscle Soreness for Dynamic Contractions: A Preliminary Study

Delayed onset muscle soreness (DOMS) indicates the presence of muscle damage and impairs force production and control. Monitorization of DOMS is useful to improving recovery intervention plans. The magnitude of DOMS may relate to muscle fatigue, which can be monitored by surface electromyography (EMG). Additionally, growing interest has been expressed in determining whether the skin temperature over a muscle group during exercise to fatigue could be a non-invasive marker for DOMS. Here we determine whether skin temperature and manifestations of muscle fatigue during exercise are correlated and can predict DOMS after concentric-eccentric bicep curl exercises. We tested 10 young adults who performed concentric-eccentric bicep curl exercises to induce muscle damage in the biceps brachialis to investigate the relationship between skin temperature and fatigue during exercise and DOMS after exercise. Muscle activation and skin temperature were recorded during exercise. DOMS was evaluated 24 h after exercise. Data analysis was performed using Bayesian regression models with regularizing priors. We found significant muscle fatigue and an increase in skin temperature during exercise. DOMS was observed 24 h after exercise. The regression models showed no correlation of changes in skin temperature and muscle fatigue during exercise with DOMS 24 h after exercise. In conclusion, our preliminary results do not support a relationship between skin temperature measured during exercise and either muscle fatigue during exercise or the ability to predict DOMS 24 h after exercise.

Individual Responses to Heat Stress: Implications for Hyperthermia and Physical Work Capacity

Background

Extreme heat events are increasing in frequency, severity, and duration. It is well known that heat stress can have a negative impact on occupational health and productivity, particularly during physical work. However, there are no up-to-date reviews on how vulnerability to heat changes as a function of individual characteristics in relation to the risk of hyperthermia and work capacity loss. The objective of this narrative review is to examine the role of individual characteristics on the human heat stress response, specifically in relation to hyperthermia risk and productivity loss in hot workplaces. Finally, we aim to generate practical guidance for industrial hygienists considering our findings. Factors included in the analysis were body mass, body surface area to mass ratio, body fat, aerobic fitness and training, heat adaptation, aging, sex, and chronic health conditions.

Findings

We found the relevance of any factor to be dynamic, based on the work-type (fixed pace or relative to fitness level), work intensity (low, moderate, or heavy work), climate type (humidity, clothing vapor resistance), and variable of interest (risk of hyperthermia or likelihood of productivity loss). Heat adaptation, high aerobic fitness, and having a large body mass are the most protective factors during heat exposure. Primary detrimental factors include low fitness, low body mass, and lack of heat adaptation. Aging beyond 50 years, being female, and diabetes are less impactful negative factors, since their independent effect is quite small in well matched participants. Skin surface area to mass ratio, body composition, hypertension, and cardiovascular disease are not strong independent predictors of the heat stress response.

Conclusion

Understanding how individual factors impact responses to heat stress is necessary for the prediction of heat wave impacts on occupational health and work capacity. The recommendations provided in this report could be utilized to help curtail hyperthermia risk and productivity losses induced by heat.

Redox basis of exercise physiology

Redox reactions control fundamental processes of human biology. Therefore, it is safe to assume that the responses and adaptations to exercise are, at least in part, mediated by redox reactions. In this review, we are trying to show that redox reactions are the basis of exercise physiology by outlining the redox signaling pathways that regulate four characteristic acute exercise-induced responses (muscle contractile function, glucose uptake, blood flow and bioenergetics) and four chronic exercise-induced adaptations (mitochondrial biogenesis, muscle hypertrophy, angiogenesis and redox homeostasis). Based on our analysis, we argue that redox regulation should be acknowledged as central to exercise physiology.

The Effect of a 7-Week Training Period on Changes in Skin NADH Fluorescence in Highly Trained Athletes

The study aimed to evaluate the changes of nicotinamide adenine dinucleotide (NADH) fluorescence in the reduced form in the superficial skin layer, resulting from a 7-week training period in highly trained competitive athletes (n = 41). The newly, non-invasive flow mediated skin fluorescence (FMSF) method was implemented to indirectly evaluate the mitochondrial activity by NADH fluorescence. The FMSF measurements were taken before and after an exercise treadmill test until exhaustion. We found that athletes showed higher post-training values in basal NADH fluorescence (pre-exercise: 41% increase; post-exercise: 49% increase). Maximum NADH fluorescence was also higher after training both pre- (42% increase) and post-exercise (47% increase). Similar changes have been revealed before and after exercise for minimal NADH fluorescence (before exercise: 39% increase; after exercise: 47% increase). In conclusion, physical training results in an increase in the skin NADH fluorescence levels at rest and after exercise in athletes.

Does the type of foam roller influence the recovery rate, thermal response and DOMS prevention?

PURPOSE

Supporting post-exercise recovery requires choosing not only the right treatment but also the equipment, in which the impact is not always clear. The study aimed to determine the effect of foam rolling on the rate of lactate removal and DOMS prevention and whether the type of foam roller is effective in the context of post-exercise recovery.

METHODS

This randomized trial enrolled 33 active healthy males divided into three groups of eleven individuals: foam rolling with a smooth (STH) or grid roller (GRID) or passive recovery (PAS). All the participants performed full squat jumps for one minute. Examination took place at rest (thermal imaging of skin temperature-[Tsk] and blood lactate-[LA]), immediately following exercise (Tsk & LA), immediately after recovery treatment (Tsk) and after 30 minutes of rest (Tsk & LA). Their pain levels were assessed using the Visual Analog Scale (VAS) 24, 48, 72, and 96 hours after exercise.

RESULTS

The magnitude of lactate decrease depended on the type of recovery used. In the PAS group, the decrease in lactate concentration by 2.65 mmol/L following a half-hour rest was significantly lower than that in the other groups (STH vs. PAS p = 0.042 / GRID vs. PAS p = 0.025). For thermal responses, significant differences between both experimental groups were noted only 30 minutes after exercise. A significant decrease in pain in the STH group occurred between 48 and 96 hours, while the GRID group showed a systematic significant decrease in VAS values in subsequent measurements. Changes in VAS values in subsequent measurements in the PAS group were not statistically significant (p>0.05).

CONCLUSIONS

Foam rolling seems to be effective for enhancing lactate clearance and counteracting DOMS, but the type of foam roller does not seem to influence the recovery rate.

Health impacts of seated arm ergometry training in patients with a diabetic foot ulcer: protocol for a randomised controlled trial

INTRODUCTION

Once diagnosed with a diabetic foot ulcer (DFU), patients are advised to offload, keeping pressure off the foot in order to facilitate ulcer healing. An increase in offloading is often accompanied by reductions in physical activity which can worsen the overall health of patients.While unable to perform traditional forms of upright activity, one mode of exercise that would allow patients to be physically active while adhering to offloading instruction is seated arm ergometry. The merits of tailored aerobic exercise in DFU remain unexplored.

METHODS AND ANALYSIS

This is a prospective open-label randomised controlled trial. Participants will be randomised to one of two groups, an exercise intervention group or control. The intervention group are required to undertake arm ergometry training at a moderate intensity (65%-75% HRpeak), three times per week for 12 weeks as individually prescribed by an exercise physiologist, while the control group will continue to receive standard care alone. Assessment of outcome measures will occur at baseline and after the intervention period, these will include: a seated VO₂ peak test, a blood sample, a short physical performance battery, a dual-energy X-ray absorptiometry scan and completing a range of health-based questionnaires. The above will be used to determine: cardiorespiratory fitness, metabolic health, physical function, body composition and quality of life, respectively. Ulcer area will also be measured as an approximate marker of ulcer healing.

ETHICS AND DISSEMINATION

This trial has been approved by 'Yorkshire & The Humber-Leeds West Research Ethics Committee' (19/YH/0269). Trial results will be published in peer-reviewed journals and through conference presentations.

TRIAL REGISTRATION NUMBER

ISRCTN16000053. Registered in accordance with WHO Trial Registration Data Set (version 1.3.1).

Physiological stressor impact on peripheral facial temperature, Il-6 and mean arterial pressure, in young people

Nowadays, stress is part of everyday life, whose long-term effects can trigger health risks. Among the main alterations that occur in the human body we can find the variation of inflammatory activity, blood pressure, and facial peripheral temperature. The objective of this work is to show the facial thermal behavior for men and women, as well as the differences in vascular and inflammatory responses induced by the effect of acute social stress. The Trier Social Stress Test was applied to 15 women and 15 men, free of disease, with an average age of 23.8 years and a standard deviation of 5.52. After capturing the baseline state, and at the end of the test, the inflammatory activity was measured through salivary interleukin-6; the mean blood pressure, and the capture of facial thermographic images. For the thermal images, six regions of interest (biothermomarkers) were analyzed: forehead, right cheek, left cheek, chin, nose, and corrugator muscle. The results obtained after analyzing the information were: an increase in inflammatory activity, an increase in mean blood pressure, and significant temperature changes in different areas of interest of the face, depending on gender. For men, it only appeared in the region of the nose and women's forehead, cheeks, and nose. Furthermore, the correlation between the three variables (il-6, blood pressure, and temperature) was performed and no significant values were found. Regarding the relationship between genders, only significant values were found for il-6.

Holistic dermatology: An evidence-based review of modifiable lifestyle factor associations with dermatologic disorders

BACKGROUND

Holistic dermatology focuses on treating the human body as a whole and implementing lifestyle changes to enhance the treatment and prognosis of skin disease. Understanding the interplay between modifiable lifestyle factors and patients' dermatologic health will help physicians better inform patients on self-care methods to mitigate the burden of their skin disease(s).

OBJECTIVE

To review the current scientific literature on the relationship between modifiable lifestyle factors and the dermatologic outcome of skin disorders.

METHODS

A systematic literature search on PubMed, Cochrane, and Web of Science was conducted to identify research articles examining the relationship between dermatology and 6 major categories of modifiable lifestyle factors: diet, sleep, exercise, stress, alcohol, and smoking.

RESULTS

A substantial amount of evidence supports the relationship between modifiable lifestyle factors and dermatologic outcomes. There were the most studies on diet, stress, alcohol, and smoking, but all lifestyle factors were supported by some degree of scientific evidence.

CONCLUSION

All modifiable lifestyle factors explored in this review play a critical role in modulating the onset and progression of skin disease. We anticipate more research studies in the future and an increasing integration of holistic dermatology into patient care.

The immediate effects of kinesiology taping on cutaneous blood flow in healthy humans under resting conditions: A randomised controlled repeated-measures laboratory study

BACKGROUND

Kinesiology taping (KT) is used in musculoskeletal practice for preventive and rehabilitative purposes. It is claimed that KT improves blood flow in the microcirculation by creating skin convolutions and that this reduces swelling and facilitates healing of musculoskeletal injuries. There is a paucity of physiological studies evaluating the effect of KT on cutaneous blood microcirculation.

OBJECTIVES

The purpose of this parallel-group controlled laboratory repeated measures design study was to evaluate the effects of KT on cutaneous blood microcirculation in healthy human adults using a dual wavelength (infrared and visible-red) laser Doppler Imaging (LDI) system. KT was compared with rigid taping and no taping controls to isolate the effects associated with the elasticity of KT.

METHODS

Forty-five healthy male and female human adults were allocated to one of the three interventions using constrained randomisation following the pre-intervention measurement: (i) KT (ii) ST (standard taping) (iii) NT (no taping). Cutaneous blood perfusion was measured using LDI in the ventral surface of forearm at pre-intervention, during-intervention and post-intervention in a normothermic environment at resting conditions.

RESULTS

Mixed ANOVA of both infrared and visible-red datasets revealed no statistically significant interaction between Intervention and Time. There was statistically significant main effect for Time but not Intervention.

CONCLUSION

KT does not increase cutaneous blood microcirculation in healthy human adults under resting physiological conditions in a normothermic environment. On the contrary, evidence suggests that taping, regardless of the elasticity in the tape, is associated with immediate reductions in cutaneous blood flow.

Visualizing and quantifying the impact of reactive hyperemia on cutaneous microvessels in humans

The mechanisms underlying reactive hyperemia (RH) responses in microvessels are poorly understood. Previous assessment tools have not been capable of directly visualizing microvessels during physiological stimulation in humans. Optical coherence tomography (OCT) is capable of imaging and quantifying subcutaneous microvessels as small as ~30 µm. In this study we use OCT to visualize and quantify skin microvascular changes in response to RH for the first time in humans. We also assessed the reproducibility of this technique. OCT and laser Doppler flowmetry (LDF) were used simultaneously to scan cutaneous microvessels in 10 young healthy subjects on 2 days. We applied a speckle decorrelation algorithm to assess OCT images and calculated flow rate, speed, diameter, and density parameters. Measures were obtained at rest (baseline) and 30-s following a 5-min cuff inflation (RH). All data were compared between days. The RH stimulus significantly increased (P < 0.0001) OCT-derived microvascular diameter (37.6 ± 3.4 vs. 44.5 ± 5.2 µm), flow rate (82.4 ± 23.4 vs. 240.1 ± 58.6 pl/s), speed (48 ± 5.7 vs. 101.5 ± 17.1 µm/s), density (5.1 ± 1.7 vs. 14.6 ± 2.6%), and also LDF-derived flux (12.3 ± 5.7 vs. 31.6 ± 9.1 perfusion units). At baseline, OCT-derived diameter (r = 0.55), flow rate (r = 0.64), speed (r = 0.55), and density (r = 0.75) showed significant between-day correlations (P < 0.05), as did LDF results (r = 0.74). In response to RH, OCT-derived diameter (r = 0.63) and density (r = 0.64) showed significant correlations (P < 0.05), whereas flow rate (r = 0.45), speed (r = 0.43), and LDF (r = 0.26) were less reproducible. Our study is novel in that it establishes the feasibility of using OCT to visualize and quantify microvascular structure and function responses to RH in humans.NEW & NOTEWORTHY This study describes the first evidence in humans that optical coherence tomography provides direct visualization and comprehensive quantification of cutaneous microvascular hemodynamics as a response to reactive hyperemia. This imaging technique will greatly improve human cutaneous microvascular assessment in physiological and clinical settings.

Assessment of the human cutaneous microvasculature using optical coherence tomography: Proving Harvey's proof

William Harvey proved the circulation of blood 400 years ago using a combination of ligature application and astute observation that presaged the existence of capillaries. Here we report findings, based on our development of a novel application of optical coherence tomography (OCT), that directly confirm the impact of cuff inflation on microvessels as small as ~30µm. By emulating Harvey's proofs, using cuff inflation at low pressure in the presence and absence of skin heating, we have imaged and quantified significant effects on microvascular diameter and density in humans in vivo. The application of cuff pressure significantly increased microvascular diameter (40.5 ± 4.6 vs 47.1 ± 3.9 µm, P = .01) and density (8.33 ± 4.3 vs 15.1 ± 4.9%, P < .01). These impacts were reversed by cuff deflation. Our study also showed the profound impacts of skin heating on microvessel diameter (46.7 ± 5.8 vs 70.6 ± 7.8 µm, P < .01) and density (14.2 ± 6.5 vs 43.2 ± 9%, P < .01) in vivo, which were further exacerbated by cuff inflation. Our approach to the direct visualization of the human skin microvasculature is non-invasive, safe, and easily applied. Future experiments might be directed at questions of microvascular physiology and pathophysiology, such as how different mammals thermoregulate and what impacts cardiovascular disease and diabetes have on microvascular structure and function.

The Neglected Leg Lymphatic Vascular Changes in the Pathomechanism of Delayed Onset Muscle Soreness in Runners

Background: Delayed onset muscle soreness (DOMS) in runners is classified as a leg muscle strain injury and presents with tenderness or stiffness to palpation and movement limitation. Most attention is directed at muscles but not at the mass of other limb soft tissues, including their lymphatic vasculature, although they undergo mechanical stress and bruises, edema, nail destruction, and pains contributing to symptoms. Methods and Results: The study was done on lower limbs of long-distance runners suffering from DOMS complaints. There were 16 runners, 11 males and 5 females, age 22-28, practicing long-distance running over the last 5 years, with body mass index (BMI) 23 ± 4. Inclusion criteria: three to five marathon runs per year and daily 3-5 km slow runs. Last long distance run 3 to 7 days before the investigation. Controls were six subjects initiating running, of the same age group and BMI. Testing of blood and lymph flow was done before and after standard ergometer 300 W 30 minutes cycling. The measurement methods were leg and big toe venous plethysmography, big toe capillary Doppler, tonometry of skin and deep tissues, lymphoscintigraphy, and indocyanine green (ICG) fluorescent lymphography. (a) Strain gauge plethysmography of the calf and big toe revealed a two- to three-times higher venous capacity in runners than in controls, (b) the increased toe venous capacity was confirmed by point Doppler recordings showing two- to three-times higher blood capillary flow compared to controls, (c) lymphoscintigraphy revealed retention of tracer in feet, dilated superficial and deep lymphatics, and enlarged popliteal and inguinal lymph nodes, and (d) ICG lymphograms showed confluents of accumulated fluid in foot and calf subcutaneous tissue with fluorescence level reaching 40%-50% compared to 20% in controls. Conclusion: Our results show that, 3-5 days after run, not only muscles but also skin and subcutaneous tissue reveal major tissue fluid accumulation, an overload bringing about functional lymphatic transport insufficiency. This may be an additional factor responsible for DOMS symptoms.

The relation between central variables, electromyography signals and peripheral microcirculation during intensive treadmill exercise

BACKGROUND

Aerobic exercise under muscle fatigue can lead to muscular damage and injuries. Finding the correlations between central and peripheral microcirculation variables, as well as with electromyography signals of leg muscles during aerobic exercise, may contribute to early muscle fatigue identification. The goal of this study was to characterize the peripheral compensation following intensive exercise for assessment of muscle performance based on non-invasive techniques.

METHODS

The experimental protocol included two days of measurements. Electrocardiography tests and anthropometric measurements of the volunteers (N = 14) were carried out. The maximal aerobic ability (first day), as well as electromyography and cutaneous hemodynamic variables (second day) were measured during treadmill run. A score-based Bayesian network machine-learning algorithm was used to predict ventilation values based on cutaneous hemodynamic measurements.

FINDINGS

Transcutaneous oxygen tension can be used to identify anaerobic threshold for both trained and untrained subjects during treadmill running, while electromyography can be used to identify anaerobic threshold only of trained subjects. Predicted values of ventilation, based on the transcutaneous oxygen tension, showed high correlation with actual values. Prediction accuracy was better among trained subjects, compared to the untrained ones.

INTERPRETATION

Transcutaneous oxygen tension could be used for prediction of maximal oxygen consumption during intense exercise and thus may provide improved assessment of premature fatigue during exercise.

The response of peripheral microcirculation to gravity-induced changes

BACKGROUND

The peripheral microcirculation supplies fresh blood to the small blood vessels, providing oxygen and nutrients to the tissues, removing waste, and maintaining normal homeostatic conditions. The goal of this study was to characterize the response of the peripheral microcirculation, in terms of blood flow and tissue oxygenation variables, to gravity-induced changes.

METHODS

The study included 20 healthy volunteers and the experiment involved monitoring central and peripheral variables with the right hand positioned at different heights. These positions correspond to various gravitational levels. Peripheral perfusion and oxygenation were monitored using a laser Doppler flowmeter, photoplethysmograph, and transcutaneous oxygen tension monitor. Local blood pressure and respiration rate were also measured.

FINDINGS

At the heart level, tissue oxygenation displayed a nadir, while capillary flow displayed a peak. Similar but weaker changes were observed at the control hand. In contrast, the photoplethysmograph's amplitude strongly decreased upon reducing the arm position below heart level. Both systolic and diastolic pressures decreased linearly between the highest to lowest arm position.

INTERPRETATION

The results may reflect peripheral compensation mechanisms, as well as an interaction between the central and peripheral cardiovascular systems, in response to local changes in blood pressure. The observed dependence of the oxygenation pattern on height could lead to important new insights for the diagnosis and treatment of problems in the regulation of tissue perfusion.

The impact of exercise frequency upon microvascular endothelium function and oxidative stress among patients with coronary artery disease

PURPOSE

This study compared the effects of low and high weekly exercise frequencies on microvascular endothelium function and oxidative stress among patients with coronary artery disease.

METHODS

Thirty-four male patients completed a 6-month cardiac rehabilitation programme, from which 23 performed exercise with a high frequency (HF) and 11 with a low frequency (LF). Systemic microvascular blood flow, maximal aerobic capacity, blood lipids, oxidative stress and anthropometric data were assessed prior to and after the cardiac rehabilitation programme. Microvascular blood flow was assessed in the skin of the forearm using laser speckle contrast imaging coupled with iontophoresis of acetylcholine.

RESULTS

Maximal aerobic capacity, biochemical analysis and anthropometric data were similar between groups prior to and after the cardiac rehabilitation programme (P>0·05). However, after 6 months of cardiac rehabilitation performed with HF, there was an increase in the peak response to acetylcholine compared with LF (83·5 ± 58·5 versus 21·8 ± 22·4%; P<0·05). Changes in lipid peroxidation (HF: -5·5 ± 9·4 versus LF: 2·2 ± 12·0 pmol MDA mg^-1 ; P = 0·19), catalase activity (HF: 0·07 ± 0·17 versus LF: 0·04 ± 0·08 U mg^-1 ; P = 0·74) and nitric oxide levels (HF: 1·8 ± 15·3 versus LF: -3·2 ± 12·3 μM; P = 0·36) were similar between groups after cardiac rehabilitation.

CONCLUSION

Six months of aerobic exercise training performed with high frequency is preferable to low frequency aiming endothelium microvascular function increases in patients with coronary artery disease. The mechanisms involved in this response are unclear and warrant additional research.