Skin Vascular Conductance Research Articles

Effects of physical activity on vascular function in autoimmune rheumatic diseases: a systematic review and meta-analysis.

To summarize existing evidence and quantify the effects of physical activity on vascular function and structure in autoimmune rheumatic diseases (ARDs). Databases were searched (through March 2020) for clinical trials evaluating the effects of physical activity interventions on markers of micro- and macrovascular function and macrovascular structure in ARDs. Studies were combined using random effects meta-analysis, which was conducted using Hedges' g. Meta-analyses were performed on each of the following outcomes: microvascular function [i.e. skin blood flow or vascular conductance responses to acetylcholine (ACh) or sodium nitropusside (SNP) administration]; macrovascular function [i.e. brachial flow-mediated dilation (FMD%) or brachial responses to glyceryl trinitrate (GTN%); and macrovascular structure [i.e. aortic pulse wave velocity (PWV)]. Ten studies (11 trials) with a total of 355 participants were included in this review. Physical activity promoted significant improvements in microvascular [skin blood flow responses to ACh, g = 0.92 (95% CI 0.42, 1.42)] and macrovascular function [FMD%, g = 0.94 (95% CI 0.56, 1.02); GTN%, g = 0.53 (95% CI 0.09, 0.98)]. Conversely, there was no evidence for beneficial effects of physical activity on macrovascular structure [PWV, g = -0.41 (95% CI -1.13, 0.32)]. Overall, the available clinical trials demonstrated a beneficial effect of physical activity on markers of micro- and macrovascular function but not on macrovascular structure in patients with ARDs. The broad beneficial impact of physical activity across the vasculature identified in this review support its role as an effective non-pharmacological management strategy for patients with ARDs.

Effects of cooling or warming of the distal upper limb on skin vascular conductance and brachial artery shear profiles during cycling exercise

ABSTRACT The relative influence of skin vascular conductance in glabrous (G; palm) and non-glabrous (NG; dorsal and forearm) regions to upstream brachial artery-shear stress (BA-SS) profile are unknown. This study aimed to elucidate the effects of G and/or NG skin vascular conductance (VC), which were modulated by warming or cooling manipulation, on BA-shear rate (SR, an estimate of SS) during cycling exercise. Seven healthy subjects performed 60-min exercise. Between 20 and 50 min of the exercise, the NG+G or G skin region were warmed to 42°C or cooled to 15°C using a water bath. Throughout the protocol, diameter and blood velocity in BA and skin VCs in forearm and palm were measured. All measurements showed that a steady-state response was reached after 20 min of exercise. Subsequently, during cooling manipulation, forearm VC was significantly decreased, and the concomitant BA-SR profile was revealed (primarily characterized by decreased antegrade SR and increased retrograde SR) in the NG+G. Such changes were not observed in G alone. During warming manipulation, forearm VC and mean BA-SR significantly increased only in the NG+G. In conclusion, vascular response in NG skin possibly plays a major role in the modulation of BA-SS profile during cycling exercise.

Dietary nitrate supplementation does not influence thermoregulatory or cardiovascular strain in older individuals during severe ambient heat stress.

What is the central question of this study? Does dietary nitrate supplementation with beetroot juice attenuate thermoregulatory and cardiovascular strain in older adults during severe heat stress? What is the main finding and its importance? A 7-day nitrate supplementation regimen lowered resting mean arterial pressure in thermoneutral conditions. During heat stress, core and mean skin temperatures, vasodilatory responses, sweat loss, heart rate and left ventricular function were unchanged, and mean arterial pressure was only transiently reduced, post-supplementation. These data suggest nitrate supplementation with beetroot juice does not mitigate thermoregulatory or cardiovascular strain in heat-stressed older individuals. This study tested the hypothesis that dietary nitrate supplementation with concentrated beetroot juice attenuates thermoregulatory and cardiovascular strain in older individuals during environmental heat stress. Nine healthy older individuals (six females, three males; aged 67±5years) were exposed to 42.5±0.1°C and 34.0±0.5% relative humidity conditions for 120min before (CON) and after 7days of dietary nitrate supplementation with concentrated beetroot juice (BRJ; 280ml, ∼16.8mmol of nitrate daily). Core and skin temperatures, body mass changes (indicative of whole-body sweat loss), skin blood flow and cutaneous vascular conductance, forearm blood flow and vascular conductance, heart rate, arterial blood pressures and indices of cardiac function were measured. The 7-day beetroot juice regimen increased plasma nitrate/nitrite levels from 27.4±15.2 to 477.0±102.5μmoll-1 (P<0.01) and lowered resting mean arterial pressure from 90±7 to 83±10mmHg at baseline under thermoneutral conditions (P=0.02). However, during subsequent heat stress, no differences in core and skin temperatures, skin blood flow and vascular conductance, forearm blood flow and vascular conductance, whole-body sweat loss, heart rate, and echocardiographic indices of systolic function and diastolic filling were evident following nitrate supplementation (all P>0.05). Mean arterial pressure was lower in BRJ vs. CON during heat stress (treatment-by-time interaction: P=0.02). Overall, these findings suggest that dietary nitrate supplementation with concentrated beetroot juice does not attenuate thermoregulatory or cardiovascular strain in older individuals exposed to severe ambient heat stress.

Pre‐clinical identification of potential molecular diagnostic biomarkers of secondary ischemia in microvascular fasciocutaneous flaps

Compromise of surgical microvascular flaps due to acute or late post‐operative circulatory complications remains a significant clinical problem worldwide. Timely detection of vessel occlusion may salvage a flap from necrosis, but monitoring of physical flap appearance is not always feasible and the etiology of compromise is hard to identify. Here we used a translational laboratory animal model of abdominal wall repair and Affymetrix gene expression microarray platform to reveal the molecular tissue and wound fluid markers of the arterial (AO), venous (VO) or mixed arterio‐venous (AVO) thrombosis of the pedicled flap in vivo. Bilateral 7×2.5cm epigastric flaps were raised in ~12 month old male and female Sprague‐Dawley retired breeder rats. Baseline fasciocutaneous tissue sample biopsies were obtained from the upper abdominal quadrants of sixteen sex‐matched rats prior to flap elevation. All flaps were then subjected to primary ischemia (PI), which was induced for 4 h by temporary clamping of superficial inferior epigastric artery (SIEA) and vein (SIEV) vessels to mimic free tissue transfer and anastomosis. Normoxic control (NC) samples were obtained from flaps after 24 h of non‐obstructed reperfusion. AO, VO or AVO samples were retrieved from paired flaps undergoing secondary ischemia (SI), in which SIEA, SIEV or both vessels were ligated for 4 h following 20 h of reperfusion. Total RNA was isolated from individual animal samples (n=8/gender group) and then pooled at equal concentrations prior to assessment of RNA quality. We observed 5011 (in males) and 4457 (in females) differentially expressed genes (DEGs) that demonstrated more than 2‐fold change in NC versus baseline conditions. There were 1403, 1643 and 2351 DEGs in male AO, VO and AVO flaps when compared to NC. In females, AO, VO and AVO‐associated DEG numbers were smaller (1074, 828 and 1518, respectively). Independently of gender, downregulation of keratinocyte‐specific small proline‐rich protein 4 (Sprr4) and upregulation of ankyrin repeat domain 37 (Ankrd37), previously identified as a target of hypoxia inducible factor‐1 (HIF‐1) gene, was significantly associated with the arterial SI. Venous SI was characterized by overexpression of major hematopoietic cell proteins (Gypa, Slc4a1, Lgals5, Hbq1b, Hemgn, Add2, Alas2), anti‐inflammatory bioactive lipid mediator arachidonate 15‐lipoxygenase (Alox15), CDK‐activating dual specificity phosphatase Cdc25B and Neuropeptide Y (Npy) ‐ an important neurotransmitter in skin vascular conductance. Upregulation of the latter genes distinguished VO not only from AO, but also from AVO. Finally, we identified 58 “master” DEGs shared by both genders that were present in SI regardless of its type (AO, VO, and AVO). Of these, “first‐tier” proteins included leukemia inhibitory factor (LIF), Depp1 autophagy regulator, adrenomedullin (Adm), growth arrest and DNA‐damage‐inducible, gamma (Gadd45g) and DNA‐damage‐inducible transcript 4 (Ddit4). Change in selected gene expression was further confirmed at protein or mRNA level by Western blotting or RT‐PCR analyses. In summary, our data revealed several SI‐associated diagnostic biomarkers that merit further investigation and, ultimately, validation in the human clinical trial setting.Support or Funding InformationThis work has been funded and supported by the Department of Otolaryngology ‐ Head &amp; Neck Surgery, Thomas Jefferson UniversityThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Skin Perfusion and Vascular Conductance during Steady State Exercise are Unaffected by Aging or Heart Disease

Skin Perfusion and Vascular Conductance during Steady State Exercise are Unaffected by Aging or Heart Disease

Facial skin blood flow responses during exposures to emotionally charged movies.

The changes in regional facial skin blood flow and vascular conductance have been assessed for the first time with noninvasive two-dimensional laser speckle flowmetry during audiovisually elicited emotional challenges for 2min (comedy, landscape, and horror movie) in 12 subjects. Limb skin blood flow and vascular conductance and systemic cardiovascular variables were simultaneously measured. The extents of pleasantness and consciousness for each emotional stimulus were estimated by the subjective rating from -5 (the most unpleasant; the most unconscious) to +5 (the most pleasant; the most conscious). Facial skin blood flow and vascular conductance, especially in the lips, decreased during viewing of comedy and horror movies, whereas they did not change during viewing of a landscape movie. The decreases in facial skin blood flow and vascular conductance were the greatest with the comedy movie. The changes in lip, cheek, and chin skin blood flow negatively correlated (P<0.05) with the subjective ratings of pleasantness and consciousness. The changes in lip skin vascular conductance negatively correlated (P<0.05) with the subjective rating of pleasantness, while the changes in infraorbital, subnasal, and chin skin vascular conductance negatively correlated (P<0.05) with the subjective rating of consciousness. However, none of the changes in limb skin blood flow and vascular conductance and systemic hemodynamics correlated with the subjective ratings. The mental arithmetic task did not alter facial and limb skin blood flows, although the task influenced systemic cardiovascular variables. These findings suggest that the more emotional status becomes pleasant or conscious, the more neurally mediated vasoconstriction may occur in facial skin blood vessels.

Effects of hypervolemia by protein and glucose supplementation during aerobic training on thermal and arterial pressure regulations in hypertensive older men.

In Japan, the incidence of heat illness in older people has rapidly increased during midsummer in the last decade, and we suggested that whey-protein+carbohydrate supplementation during aerobic training would increased plasma volume (PV) to enhance thermoregulatory adaptation in older men (J Appl Physiol 107: 725-733, 2009); however, >60% of people age 65 and older suffer from hypertension, and the symptoms may be worsened by hypervolemia. To examine this, we randomly divided 21 older men (∼69 yr) with ∼160 mmHg for systolic and ∼90 mmHg for diastolic blood pressure at rest into two groups: Glc (n = 11) consuming glucose alone (25 g) and Pro-Glc (n = 10) consuming whey protein (10 g) + glucose (15 g), immediately after cycling exercise at 60-75% of peak aerobic capacity (V̇o2 peak) for 60 min/day, 3 days/wk, for 8 wk. Before and after training, we measured PV (dye dilution), baroreflex sensitivity (BRS) of heart rate (Valsalva maneuver), and carotid arterial compliance (CAC) from carotid arterial diameter (ultrasound imaging) responses to pulsatile arterial pressure change (photoplethysmography) at rest. Additionally, we measured esophageal temperature (Tes) and forearm skin blood flow (plethysmography) during exercise at 60% pretraining V̇o2 peak for 20 min in a warm environment. We found that the forearm skin vascular conductance response to increased Tes was enhanced in Pro-Glc with increased PV, but this was not found in Glc; however, despite the increased PV, arterial blood pressures rather decreased with increased CAC and BRS in Pro-Glc. Thus, the prescription was applicable to older men with hypertension to prevent heat illness during exercise.

Mechanisms of Pronounced and Sustained Cutaneous Vasoconstriction during Cryotherapy

Cryotherapy is a common therapeutic technique using ice or cold water to reduce local blood flow. While beneficial, it can be associated with some negative physiological side effects such as pronounced tissue ischemia sustained for hours during a post-treatment rewarming period. Previous findings in our laboratory have indicated that this cutaneous vasoconstriction during cryotherapy is abolished following blockade of Rho Kinase. The Rho Kinase enhances vasoconstriction in part via down regulation of nitric oxide synthase (NOS). PURPOSE: To test the hypothesis that a reduction in nitric oxide (NO) bioavailability is involved in the pronounced and sustained cutaneous vasoconstriction that occurs during a typical cyrotherapy protocol. METHODS: 8 healthy individuals (6 male) participated in this protocol. A cryotherapy unit with a water perfused bladder was used. The bladder was placed on the lateral portion of the calf. Four microdialysis membranes were placed in the skin underneath the bladder. One site was perfused with lactated ringers (CON); neuronal NOS (nNOS) was blocked in another site (NPLA); endothelial NOS (eNOS) was blocked in another site (NLIO); and the last site received non-selective NOS blockade (LNAME). All solutions were dissolved in sterile lactated Ringers. Skin temperature (SkT) and skin vascular conductance (SkVC) was measured at each site. 0 °C water perfused through the cryotherapy bladder for 30 min, followed by passive rewarming (i.e. water shut off) for 1 hr, followed by direct heating with 46 °C water for 10 min. RESULTS: SkT fell from 34°C to 19°C during 30 min of cooling in all sites. SkVC at CON was reduced ~75% after 30 min of cooling and was similar to LNAME, NPLA, and LNIO (78, 75, 77%, reduction respectively; P>0.05). During passive rewarming SkVC remained blunted to a similar degree at all sites (Con: 87±1, LNAME: 85±2, NPLA: 87±2, LNIO: 85±1 % reduction; P>0.05). SkVC during 10 min of active warming was also similar between sites (CON: 62%, LNAME: 65%, NPLA: 67%, and LNIO: 68% reduction; P<0.05) CONCLUSION: The current data suggest that reductions in NO bioavailability do not contribute to pronounced and sustained vasoconstriction during cryotherapy. Supported by the National Institute of Biomedical Imaging and Bioengineering; R01EB015522 (Multi PI: K.R. Diller & R.M. Brothers).

Acute L-arginine supplementation has no effect on cardiovascular or thermoregulatory responses to rest, exercise, and recovery in the heat.

To investigate the effect of acute L-arginine (L-ARG) supplementation on cardiovascular and thermoregulatory responses to rest, exercise, and recovery in the heat. Eight healthy men (age 27 ± 6 years; stature 176 ± 6 cm; body mass 76 ± 4 kg; maximal power output 237 ± 39 W) participated in a double-blind, crossover study, attending the laboratory for two experimental trials. On each occasion, participants consumed 500 ml of a black currant-flavoured cordial beverage 30 min before completing a 90 min experiment in the heat (35 °C and 50% rh). The experiment consisted of 30 min of seated rest, followed by 30 min submaximal cycling (60% maximal power output) and 30 min passive seated recovery. On one visit the drink contained 10 g of dissolved L-ARG while on the other visit it did not. L-ARG supplementation increased plasma L-ARG concentrations (peak +223 ± 80% after 60 min of the 90 min experiment); however, supplementation had no effect on rectal temperature, mean skin temperature, heart rate, arterial pressure, forearm skin vascular conductance, oxygen consumption or sweat loss at rest, during exercise, or during recovery in the heat (p > 0.05). Acute ingestion of 10 g L-ARG supplementation failed to elicit any changes in the cardiovascular or thermoregulatory responses to active or passive heat exposure in young, healthy males.

Adrenergic Control of the Cutaneous Circulation during Cryotherapy

Cryotherapy application is a widely clinically used therapeutic technique using ice or cold water applied to the skin surface to reduce local blood flow. While beneficial, cryotherapy treatment does have the potential to induce some detrimental physiological side effects. For example, cryotherapy treatment induces pronounced tissue ischemia that is sustained for hours even during a post-treatment rewarming period. PURPOSE: To investigate the role of adrenergic receptor activation on cutaneous blood flow during 30 min of cryotherapy as well as during the subsequent 1 hr of passive rewarming. We hypothesized that adrenergic-mediated vasoconstriction is involved in pronounced and sustained cutaneous vasoconstriction that occurs during cooling and passive rewarming. METHODS: To date 4 complete data sets have been collected with 2 partial, incomplete datasets. A commercially available cryotherapy unit with a water perfused bladder was used. The bladder was placed on the lateral portion of the calf. Four microdialysis membranes were threaded through the dermis of the skin directly underneath the water bladder. One site was perfused with lactated ringers solution (CON), one with bretylium tosylate (BRE), one with propranolol+yohimbine+BIBP (PBY), and one with propranolol+BIBP (PB). Skin temperature (SkT) and skin vascular conductance (SkVC) was measured at each site. Subjects had 0 °C water perfused through the cryotherapy bladder for 30 min, followed by passive rewarming (i.e. water shut off) for 1 hr, followed by direct heating with 46 °C for 10 min. RESULTS: SkT fell from 33°C to 17.7°C during 30 min of cold water application across all sites. SkVC at CON was reduced ∼80% after 30 min of cooling and was not significantly different than PB (p>0.05). Vasoconstriction was attenuated at the BRE and PBY sites during cooling compared the control (SkVC: BRE = 58% reduction, PBY = 37% reduction, CON 80% reduction (p<0.05 for each comparison). Following 10 min of active warming the BRE site was not different than CON (SkBF: 46% reduction vs. 28% reduction (P>0.05). CONCLUSION: Our preliminary finding was that adrenergic function mediates the vasoconstriction that occurs with cryotherapy application. This is in line with previous literature investigating the adrenergic mechanisms of vasoconstriction with skin cooling.

Mechanisms of Pronounced and Sustained Cutaneous Vasoconstriction During Cryotherapy

Cryotherapy is a therapeutic technique using ice or cold water applied to the skin to reduce local blood flow. While beneficial, there are some side effects such as pronounced vasoconstriction and tissue ischemia that is sustained for hours post‐treatment. This study tested the hypothesis that sustained vasoconstriction is mediated by 1) Rho‐kinase and/or 2) elevated oxidative stress. 13 subjects were fitted with a commercially available cryotherapy unit with a water perfused bladder on the lateral portion of the right calf. 3 microdialysis membranes were threaded through the dermis underneath the bladder. One site received lactated ringers (CON), one received the Rho‐Kinase inhibitor Fasudil (FAS), and one received ascorbic acid (VitC). Skin temperature (SkT) and skin vascular conductance (SkVC) was measured at each site. Subjects had 0 °C water perfused through the cryotherapy bladder for 30 min, followed by passive rewarming for 2 hr. SkT fell from 34°C to 17.9°C cold water application across all sites. SkVC was reduced after 30 min of cooling with both FAS and VitC having attenuated vasoconstriction when compared to CON (P&lt;0.05 for both). After 2 hr of passive rewarming SkVC was elevated at the FAS site where as it remained reduced CON and VitC sites (p&lt;0.05). These findings indicate Rho‐kinase and oxidative stress contribute to pronounced vasoconstriction during cryotherapy and that the Rho‐kinase contributes to sustained vasoconstriction during the rewarming period post treatmentSupported by the National Institute of Biomedical Imaging and Bioengineering; R01EB015522 (Multi PI: K.D. Diller &amp; R.M. Brothers).

Skin and cerebral vascular function/reactivity in healthy young adult african americans

African Americans (AA) are at an increased risk for cardio and cerebral vascular disease relative to Caucasians (CA) and the underlying impairments manifest as early as the second generation prior to overt signs of risk. The mechanisms of this increased risk are multifactorial; however, evidence suggests that microvascular dysfunction is a primary contributor. This study tested the hypothesis that microvascular function, indexed by the skin vascular conductance (SkVc) response to local heating, is impaired in young otherwise healthy AAs. Furthermore, we hypothesized that AAs have an attenuated cerebral vasodilator response to hypercapnia. To date complete data sets have has been collected on 5 AAs and 6 CAs. SkVc was assessed while the skin was clamped at 34 °C and 40 °C and values were normalized to a maximal value obtained during heating at 43 °C for 30 min. Cerebral vasomotor reactivity (CVMR) was assessed by increases in cerebral vascular conductance (CVC) during a rebreathing protocol. CVC was reduced in the AAs at 34 °C (AA: 10±3 % max vs. CA: 20±8 % max; P=0.01) while there was a trend for CVC to be reduced at 40 °C (AA: 57±19 % max vs. CA: 71±8 % max; P=0.12). CVMR was significantly reduced during hypercapnic rebreathing in the AAs relative to the CAs (AA: 2.7±1.0 %/Torr vs. CA: 4.0±1.1 %/Torr; P=0.01). Despite the small sample size, these data suggest that microvascular function is impaired in young otherwise healthy AAs.

Vasomotor responses in facial and finger skin to acute changes in blood pressure

We examined the effects of acute changes in blood pressure on facial and finger vasomotion in nine healthy males using laser speckle flowgraphy and laser‐dopplar flowmetry, respectively. Skin blood flow was measured during acute changes in the rise of blood pressure (using maximum static handgrip: HG), and in the reduction of blood pressure (using acute release of 2‐min thigh cuff pressure at 250mmHg: CR). Skin vascular conductance (VC) values at baseline and the first four seconds of HG and CR were calculated from the ratio of skin blood flow and mean arterial pressure. During the HG, VC in forehead, eyelid, nose, cheek and upper lip significantly increased, whereas that in finger decreased compared to the baseline. During the CR, VC in forehead, eyelid, nose, cheek, upper lip and finger significantly decreased compared to the baseline. The results obtained in finger skin were similar to previous studies (Durand et al 2004, Saad et al 2001). These results obtained in facial skin suggest that changes in VC do not serve to maintain facial skin blood flow against acute changes in blood pressure.

Cool head, hot brain: cerebral blood flow distribution during exercise

Cool head, hot brain: cerebral blood flow distribution during exercise

Effects of hypohydration on thermoregulation during exercise before and after 5-day aerobic training in a warm environment in young men

We examined whether enhanced cardiovascular and thermoregulatory responses during exercise after short-term aerobic training in a warm environment were reversed when plasma volume (PV) expansion was reversed by acute isotonic hypohydration. Seven young men performed aerobic training at the 70% peak oxygen consumption rate (Vo(₂peak)) at 30°C atmospheric temperature and 50% relative humidity, 30 min/day for 5 days. Before and after training, we performed the thermoregulatory response test while measuring esophageal temperature (T(es)), forearm skin vascular conductance, sweat rate (SR), and PV during 30 min exercise at the metabolic rate equivalent to pretraining 65% Vo(₂peak) in euhydration under the same environment as during training in four trials (euhydration and hypohydration, respectively). Hypohydration targeting 3% body mass was attained by combined treatment with low-salt meals to subjects from ~48 h before the test and administration of a diuretic ~4 h before the test. After training, the T(es) thresholds for cutaneous vasodilation and sweating decreased by 0.3 and 0.2°C (P = 0.008 and 0.012, respectively) when PV increased by ~10%. When PV before and after training was reduced to a similar level, ~10% reduction from that in euhydration before training, the training-induced reduction in the threshold for cutaneous vasodilation increased to a level similar to hypohydration before training (P = 0.093) while that for sweating remained significantly lower than that before training (P = 0.004). Thus the enhanced cutaneous vasodilation response after aerobic training in a warm environment was reversed when PV expansion was reversed while the enhanced SR response remained partially.

Combined heat and mental stress alters neurovascular control in humans.

This study examined the effect of combined heat and mental stress on neurovascular control. We hypothesized that muscle sympathetic nerve activity (MSNA) and forearm vascular responses to mental stress would be augmented during heat stress. Thirteen subjects performed 5 min of mental stress during normothermia (Tcore; 37 ± 0°C) and heat stress (38 ± 0°C). Heart rate, mean arterial pressure (MAP), MSNA, forearm vascular conductance (FVC; venous occlusion plethysmography), and forearm skin vascular conductance (SkVCf; via laser-Doppler) were analyzed. Heat stress increased heart rate, MSNA, SkVCf, and FVC at rest but did not change MAP. Mental stress increased MSNA and MAP during both thermal conditions; however, the increase in MAP during heat stress was blunted, whereas the increase in MSNA was accentuated, compared with normothermia (time × condition; P < 0.05 for both). Mental stress decreased SkVCf during heat stress but not during normothermia (time × condition, P < 0.01). Mental stress elicited similar increases in heart rate and FVC during both conditions. In one subject combined heat and mental stress induced presyncope coupled with atypical blood pressure and cutaneous vascular responses. In conclusion, these findings indicate that mental stress elicits a blunted increase of MAP during heat stress, despite greater increases in total MSNA and cutaneous vasoconstriction. The neurovascular responses to combined heat and mental stress may be clinically relevant to individuals frequently exposed to mentally demanding tasks in hyperthermic environmental conditions (i.e., soldiers, firefighters, and athletes).

Combined Heat and Mental Stress Alters Neurovascular Control in Humans

This study examined the effect of combined heat and mental stress on neurovascular control. We hypothesized that muscle sympathetic nerve activity (MSNA) and forearm vascular conductance (FVC) responses to mental stress (MS) would be augmented during heat stress (HS). Twelve subjects performed 5 min of MS during normothermia (NT: Tcore; 37 ± 0 °C) and HS (38 ± 0 °C). Heart rate (HR), mean arterial pressure (MAP), MSNA, forearm skin vascular conductance (SkVCf), and FVC were recorded. HS increased HR, MSNA, SkVCf, and FVC at rest, but did not change MAP. MS increased MAP during both conditions, but increases during HS (Δ10 ± 2 mmHg) were blunted compared to NT (Δ15 ± 1 mmHg; interaction, P&lt;0.01). MS increased total MSNA during both conditions, but increases during HS were greater (Δ4668 ± 1224 units) relative to NT (Δ1267 ± 558 units; interaction, P&lt;0.01). MS decreased SkVCf during HS (Δ−19 ± 5 units; P&lt;0.001), but not during NT (Δ−1 ± 0 units). MS elicited similar increases in MSNA burst frequency, HR, and FVC during both conditions. In conclusion, these findings indicate that MS elicits a blunted increase of MAP during HS, despite greater increases in total MSNA and cutaneous vasoconstriction. These findings could be of particular interest to those exposed to mentally demanding tasks in hyperthermic environmental conditions (i.e. soldiers, firefighters, and athletes). Supported by APS and NIH.

Influence of age, sex, and aerobic capacity on forearm and skin blood flow and vascular conductance

This study investigated the influence of age, sex, and aerobic capacity on resting and peak forearm and cutaneous blood flow (FBF, CBF). We recruited 93 female and 129 male subjects (age range 16-76 years). FBF and CBF were assessed by plethysmography and laser-Doppler flowmetry, respectively. Peak FBF was obtained following 5 min forearm vascular occlusion and peak CBF in response to local skin heating of 42 degrees C. Blood pressure was measured manually and by Finapres. Maximal oxygen uptake (VO2max) was obtained from a treadmill exercise stress test. Age was associated with declines in resting FBF (y = -1.176 ln(x) + 6.6899, r(2) = 0.45) and peak FBF (y = -17.21 ln(x) + 93.843, r(2) = 0.53) (both p < 0.05). Peak CBF decreased with increasing age (y = -223.6 ln(x) + 1,102.9, r(2) = 0.34) (p < 0.05), but resting CBF was unchanged (p > 0.05). Males had higher resting and peak FBF than females (p < 0.05) and these variables were related to ageing better in males (y = -1.245 ln(x) + 7.188, r(2) = 0.71 and y = -18.53 ln(x) + 102.82, r(2) = 0.69) than in females (y = -1.149 ln(x) + 6.4307, r(2) = 0.38 and y = -16.59 ln(x) + 88.872, r(2) = 0.55). There were no sex differences in resting CBF (p > 0.05). Peak CBF was much better related to ageing in males than females (y = -276.1 ln(x) + 1,365.4, r(2) = 0.53 vs. y = -183.1 ln(x) + 907.86, r(2) = 0.28). VO2max decreased with advancing age and this decline was associated with the decline in peak FBF (y = -0.5933x + 10.91, r(2) = 0.36, p < 0.05) but not with peak CBF (p > 0.05). These results suggest that healthy ageing is associated with a curvilinear decline in resting and peak forearm and peak cutaneous vasodilator capacity, with males more severely affected than females. The data indicate that peak FBF is influenced by VO2max but peak CBF is not.

Exercise and cardiovascular risk reduction: time to update the rationale for exercise?

although it is generally accepted that the promotion of exercise accords with clinical best practice, the anecdotal experience of many primary care physicians, cardiologists, and exercise physiologists is that, even when exercise prescriptions are adhered to, risk factors often fail to demonstrate

Ambient Temperature Affects Glabrous Skin Vasculature and Sweating Responses to Mental Task in Humans

We compared responses in heart rate (HR), mean blood pressure (MAP), sweating rate (SR), sweating expulsion (SwE), and skin vascular conductance (VC) to mental task among different ambient temperature (Ta) conditions, i.e., 12, 16, 20, and 24 degrees C. Seven subjects (27+/-5 yrs, 64+/-14 kg) underwent a 2-min color word conflict test (CWT) after 2 mins of baseline data acquisition following a 20-min resting period. All subjects wore long sleeve shirts and long pants. The skin blood flow was measured with a laser Doppler probe on the left index finger pulp to calculate skin VC, and the SR and sweating expulsion (SwE) were measured with a ventilated capsule on the left thenar. CWT significantly increased the HR and MAP, while there was no significant effect of Ta on the magnitudes of these responses. CWT significantly decreased the skin VC when the Ta was 24 degrees C, whereas it significantly increased the skin VC when the Ta was 12 or 16 degrees C. CWT significantly increased SR and SwE in all Ta conditions, and the SwE was greater in warmer conditions. These findings suggest that different ambient temperatures induce different responses in finger skin vasculature to mental task, implying the independent response of cutaneous vasomotor tone and sweat glands in glabrous skin to mental task.