scholarly journals Heat acclimation improves cutaneous vascular function and sweating in trained cyclists

2010 ◽  
Vol 109 (6) ◽  
pp. 1736-1743 ◽  
Author(s):  
Santiago Lorenzo ◽  
Christopher T. Minson
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Vascular Function ◽  
Structural Changes ◽  
Forearm Blood Flow ◽  
Sweat Rate ◽  
Local Heating ◽  
Heat Acclimation ◽  
Control Group ◽  
Doppler Flowmetry

The aim of this study was to explore heat acclimation effects on cutaneous vascular responses and sweating to local ACh infusions and local heating. We also sought to examine whether heat acclimation altered maximal skin blood flow. ACh (1, 10, and 100 mM) was infused in 20 highly trained cyclists via microdialysis before and after a 10-day heat acclimation program [two 45-min exercise bouts at 50% maximal O2 uptake (V̇o2max) in 40°C ( n = 12)] or control conditions [two 45-min exercise bouts at 50% V̇o2max in 13°C ( n = 8)]. Skin blood flow was monitored via laser-Doppler flowmetry (LDF), and cutaneous vascular conductance (CVC) was calculated as LDF ÷ mean arterial pressure. Sweat rate was measured by resistance hygrometry. Maximal brachial artery blood flow (forearm blood flow) was obtained by heating the contralateral forearm in a water spray device and measured by Doppler ultrasound. Heat acclimation increased %CVCmax responses to 1, 10, and 100 mM ACh (43.5 ± 3.4 vs. 52.6 ± 2.6% CVCmax, 67.7 ± 3.4 vs. 78.0 ± 3.0% CVCmax, and 81.0 ± 3.8 vs. 88.5 ± 1.1% CVCmax, respectively, all P < 0.05). Maximal forearm blood flow remained unchanged after heat acclimation (290.9 ± 12.7 vs. 269.9 ± 23.6 ml/min). The experimental group showed significant increases in sweating responses to 10 and 100 mM ACh (0.21 ± 0.03 vs. 0.31 ± 0.03 mg·cm−2·min−1 and 0.45 ± 0.05 vs. 0.67 ± 0.06 mg·cm−2·min−1, respectively, all P < 0.05), but not to 1 mM ACh (0.13 ± 0.02 vs. 0.18 ± 0.02 mg·cm−2·min−1, P = 0.147). No differences in any of the variables were found in the control group. Heat acclimation in highly trained subjects induced local adaptations within the skin microcirculation and sweat gland apparatus. Furthermore, maximal skin blood flow was not altered by heat acclimation, demonstrating that the observed changes were attributable to improvement in cutaneous vascular function and not to structural changes that limit maximal vasodilator capacity.

scholarly journals Ten days of repeated local forearm heating does not affect cutaneous vascular function

2017 ◽  
Vol 123 (2) ◽  
pp. 310-316 ◽  
Author(s):  
Michael A. Francisco ◽  
Vienna E. Brunt ◽  
Krista Nicole Jensen ◽  
Santiago Lorenzo ◽  
Christopher T. Minson
Keyword(s):  
Blood Flow ◽  
Young Adults ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Vascular Function ◽  
Forearm Blood Flow ◽  
Local Heating ◽  
Laser Doppler ◽  
Vascular Conductance ◽  
Doppler Flowmetry

The aim of the present study was to determine whether 10 days of repeated local heating could induce peripheral adaptations in the cutaneous vasculature and to investigate potential mechanisms of adaptation. We also assessed maximal forearm blood flow to determine whether repeated local heating affects maximal dilator capacity. Before and after 10 days of heat training consisting of 1-h exposures of the forearm to 42°C water or 32°C water (control) in the contralateral arm (randomized and counterbalanced), we assessed hyperemia to rapid local heating of the skin ( n = 14 recreationally active young subjects). In addition, sequential doses of acetylcholine (ACh, 1 and 10 mM) were infused in a subset of subjects ( n = 7) via microdialysis to study potential nonthermal microvascular adaptations following 10 days of repeated forearm heat training. Skin blood flow was assessed using laser-Doppler flowmetry, and cutaneous vascular conductance (CVC) was calculated as laser-Doppler red blood cell flux divided by mean arterial pressure. Maximal cutaneous vasodilation was achieved by heating the arm in a water-spray device for 45 min and assessed using venous occlusion plethysmography. Forearm vascular conductance (FVC) was calculated as forearm blood flow divided by mean arterial pressure. Repeated forearm heating did not increase plateau percent maximal CVC (CVCmax) responses to local heating (89 ± 3 vs. 89 ± 2% CVCmax, P = 0.19), 1 mM ACh (43 ± 9 vs. 53 ± 7% CVCmax, P = 0.76), or 10 mM ACh (61 ± 9 vs. 85 ± 7% CVCmax, P = 0.37, by 2-way repeated-measures ANOVA). There was a main effect of time at 10 mM ACh ( P = 0.03). Maximal FVC remained unchanged (0.12 ± 0.02 vs. 0.14 ± 0.02 FVC, P = 0.30). No differences were observed in the control arm. Ten days of repeated forearm heating in recreationally active young adults did not improve the microvascular responsiveness to ACh or local heating. NEW & NOTEWORTHY We show for the first time that 10 days of repeated forearm heating is not sufficient to improve cutaneous vascular responsiveness in recreationally active young adults. In addition, this is the first study to investigate cutaneous cholinergic sensitivity and forearm blood flow following repeated local heat exposure. Our data add to the limited studies regarding repeated local heating of the cutaneous vasculature.

scholarly journals Minimal role for H1 and H2 histamine receptors in cutaneous thermal hyperemia to local heating in humans

2006 ◽  
Vol 100 (2) ◽  
pp. 535-540 ◽  
Author(s):  
Brett J. Wong ◽  
Sarah J. Williams ◽  
Christopher T. Minson
Keyword(s):  
Blood Flow ◽  
Receptor Antagonist ◽  
Skin Blood Flow ◽  
Local Heating ◽  
Histamine Receptor ◽  
Receptor Activation ◽  
Control Site ◽  
Doppler Flowmetry ◽  
Histamine Receptor Antagonist ◽  
And Control

The precise mechanism(s) underlying the thermal hyperemic response to local heating of human skin are not fully understood. The purpose of this study was to investigate a potential role for H1 and H2 histamine-receptor activation in this response. Two groups of six subjects participated in two separate protocols and were instrumented with three microdialysis fibers on the ventral forearm. In both protocols, sites were randomly assigned to receive one of three treatments. In protocol 1, sites received 1) 500 μM pyrilamine maleate (H1-receptor antagonist), 2) 10 mM l-NAME to inhibit nitric oxide synthase, and 3) 500 μM pyrilamine with 10 mM NG-nitro-l-arginine methyl ester (l-NAME). In protocol 2, sites received 1) 2 mM cimetidine (H2 antagonist), 2) 10 mM l-NAME, and 3) 2 mM cimetidine with 10 mM l-NAME. A fourth site served as a control site (no microdialysis fiber). Skin sites were locally heated from a baseline of 33 to 42°C at a rate of 0.5°C/5 s, and skin blood flow was monitored using laser-Doppler flowmetry (LDF). Cutaneous vascular conductance was calculated as LDF/mean arterial pressure. To normalize skin blood flow to maximal vasodilation, microdialysis sites were perfused with 28 mM sodium nitroprusside, and control sites were heated to 43°C. In both H1 and H2 antagonist studies, no differences in initial peak or secondary plateau phase were observed between control and histamine-receptor antagonist only sites or between l-NAME and l-NAME with histamine receptor antagonist. There were no differences in nadir response between l-NAME and l-NAME with histamine-receptor antagonist. However, the nadir response in H1 antagonist sites was significantly reduced compared with control sites, but there was no effect of H2 antagonist on the nadir response. These data suggest only a modest role for H1-receptor activation in the cutaneous response to local heating as evidenced by a diminished nadir response and no role for H2-receptor activation.

scholarly journals Effects of mode of exercise recovery on thermoregulatory and cardiovascular responses

2002 ◽  
Vol 93 (6) ◽  
pp. 1918-1924 ◽  
Author(s):  
Robert Carter ◽  
Thad E. Wilson ◽  
Donald E. Watenpaugh ◽  
Michael L. Smith ◽  
Craig G. Crandall
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Heat Dissipation ◽  
Sweat Rate ◽  
Local Heating ◽  
Cardiovascular Responses ◽  
Maximal Heart Rate ◽  
Exercise Recovery ◽  
Active Recovery ◽  
Arterial Blood

To identify the effects of exercise recovery mode on cutaneous vascular conductance (CVC) and sweat rate, eight healthy adults performed two 15-min bouts of upright cycle ergometry at 60% of maximal heart rate followed by either inactive or active (loadless pedaling) recovery. An index of CVC was calculated from the ratio of laser-Doppler flux to mean arterial pressure. CVC was then expressed as a percentage of maximum (%max) as determined from local heating. At 3 min postexercise, CVC was greater during active recovery (chest: 40 ± 3, forearm: 48 ± 3%max) compared with during inactive recovery (chest: 21 ± 2, forearm: 25 ± 4%max); all P < 0.05. Moreover, at the same time point sweat rate was greater during active recovery (chest: 0.47 ± 0.10, forearm: 0.46 ± 0.10 mg · cm−2 · min−1) compared with during inactive recovery (chest: 0.28 ± 0.10, forearm: 0.14 ± 0.20 mg · cm−2 · min−1); all P < 0.05. Mean arterial blood pressure, esophageal temperature, and skin temperature were not different between recovery modes. These data suggest that skin blood flow and sweat rate during recovery from exercise may be modulated by nonthermoregulatory mechanisms and that sustained elevations in skin blood flow and sweat rate during mild active recovery may be important for postexertional heat dissipation.

Effect of functional electrostimulation on impaired skin vasodilator responses to local heating in spinal cord injury

2009 ◽  
Vol 106 (4) ◽  
pp. 1065-1071 ◽  
Author(s):  
Noortje T. L. Van Duijnhoven ◽  
Thomas W. J. Janssen ◽  
Daniel J. Green ◽  
Christopher T. Minson ◽  
Maria T. E. Hopman ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Blood Flow ◽  
Skin Blood Flow ◽  
Local Heating ◽  
Axon Reflex ◽  
Doppler Flowmetry ◽  
Cord Injury ◽  
Cutaneous Vascular Conductance ◽  
Functional Electrostimulation

Spinal cord injury (SCI) induces vascular adaptations below the level of the lesion, such as impaired cutaneous vasodilation. However, the mechanisms underlying these differences are unclear. The aim of this study is to examine arm and leg cutaneous vascular conductance (CVC) responses to local heating in 17 able-bodied controls (39 ± 13 yr) and 18 SCI subjects (42 ± 8 yr). SCI subjects were counterbalanced for functional electrostimulation (FES) cycling exercise (SCI-EX, n = 9) or control (SCI-C, n = 9) and reanalyzed after 8 wk. Arm and leg skin blood flow were measured by laser-Doppler flowmetry during local heating (42°C), resulting in an axon-reflex mediated first peak, nadir, and a primarily nitric oxide-dependent plateau phase. Data were expressed as a percentage of maximal CVC (44°C). CVC responses to local heating in the paralyzed leg, but also in the forearm of SCI subjects, were lower than in able-bodied controls ( P < 0.05 and 0.01, respectively). The 8-wk intervention did not change forearm and leg CVC responses to local heating in SCI-C and SCI-EX, but increased femoral artery diameter in SCI-EX ( P < 0.05). Interestingly, findings in skin microvessels contrast with conduit arteries, where physical (in)activity contributes to adaptations in SCI. The lower CVC responses in the paralyzed legs might suggest a role for inactivity in SCI, but the presence of impaired CVC responses in the normally active forearm suggests other mechanisms. This is supported by a lack of adaptation in skin microcirculation after FES cycle training. This might relate to the less frequent and smaller magnitude of skin blood flow responses to heat stimuli, compared with controls, than physical inactivity per se.

scholarly journals Hypertensive patients features of the microcirculation type after new coronavirus infection of COVID-19

2022 ◽  
Vol 20 (4) ◽  
pp. 45-51
Author(s):  
I. A. Zolotovskaya ◽  
G. R. Gimatdinova ◽  
I. L. Davydkin
Keyword(s):  
Blood Flow ◽  
Heart Disease ◽  
Family History ◽  
Adverse Events ◽  
Skin Blood Flow ◽  
Control Group ◽  
Doppler Flowmetry ◽  
Hypertensive Patients ◽  
History Of ◽  
And Control

Introduction. The COVID-19 pandemic multiplies the incidence of long-term adverse events. Family history of heart disease predicates the necessity of study hemostasis in hypertensive patients. The purpose was to study the microcirculation in hypertensive COVID-19 survivors. Materials and methods. We selected patients treated at the hospitals of Samara from January to March 2021. COVID-19 survivors (diagnosis was confirmed by polymerase chain reaction analysis) were divided into 2 groups and analysed: the group with family history of hypertension (167 patients) and control group with no relevant past medical history (68 patients). The main microcirculation characteristics were evaluated by laser Doppler flowmetry of skin blood flow. Results. The average age of COVID-19 survivors was 52.3±14.2 years, n=86 (51.4 %) – male. The majority of patients (n=61/36.5 %) were 45 to 54 years. A fifth of the patients (n=35/20.9 %) showed no complaints about the underlying disease, the clinical manifestations of the rest were general weakness, fever, shortness of breath, cough, headaches, unstable blood pressure, inflammation of the ENT organs. By comparison the microcirculation parameters of the case patients and control group, a decreased perfusion was detected. It requires a preventive medicine to prevent from early and distant micro and macrothrombosis. Conclusion. The study of microcirculation essential features by the LDF of skin blood flow revealed a pathological type with a predominance of vasoconstrictions in patients with a history of hypertension. Taking into account the proven increase in the incidence of thrombotic events in COVID-19 survivors, the noticed changes in microcirculation require a new approach to prevent from adverse events concerning the hypercoagulation process, especially in patients with famil y history of heart disease.

Cutaneous vascular responses to isometric handgrip exercise during local heating and hyperthermia

2005 ◽  
Vol 98 (6) ◽  
pp. 2011-2018 ◽  
Author(s):  
Gregg R. McCord ◽  
Christopher T. Minson
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Skin Blood Flow ◽  
Sweat Rate ◽  
Local Heating ◽  
Whole Body ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Hyperthermic Condition ◽  
Isometric Handgrip Exercise

The dramatic increase in skin blood flow and sweating observed during heat stress is mediated by poorly understood sympathetic cholinergic mechanisms. One theory suggests that a single sympathetic cholinergic nerve mediates cutaneous active vasodilation (AVD) and sweating via cotransmission of separate neurotransmitters, because AVD and sweating track temporally and directionally when activated during passive whole body heat stress. It has also been suggested that these responses are regulated independently, because cutaneous vascular conductance (CVC) has been shown to decrease, whereas sweat rate increases, during combined hyperthermia and isometric handgrip exercise. We tested the hypothesis that CVC decreases during isometric handgrip exercise if skin blood flow is elevated using local heating to levels similar to that induced by pronounced hyperthermia but that this does not occur at lower levels of skin blood flow. Subjects performed isometric handgrip exercise as CVC was elevated at selected sites to varying levels by local heating (which is independent of AVD) in thermoneutral and hyperthermic conditions. During thermoneutral isometric handgrip exercise, CVC decreased at sites in which blood flow was significantly elevated before exercise (−6.5 ± 1.8% of maximal CVC at 41°C and −10.5 ± 2.0% of maximal CVC at 43°C; P < 0.05 vs. preexercise). During isometric handgrip exercise in the hyperthermic condition, an observed decrease in CVC was associated with the level of CVC before exercise. Taken together, these findings argue against withdrawal of AVD to explain the decrease in CVC observed during isometric handgrip exercise in hyperthermic conditions.

The role of baseline in the cutaneous vasoconstrictor responses during combined local and whole body cooling in humans

2007 ◽  
Vol 293 (5) ◽  
pp. H3187-H3192 ◽  
Author(s):  
Gary J. Hodges ◽  
Wojciech A. Kosiba ◽  
Kun Zhao ◽  
Guy E. Alvarez ◽  
John M. Johnson
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Local Heating ◽  
Laser Doppler ◽  
Whole Body ◽  
Local Cooling ◽  
Doppler Flowmetry ◽  
Vasoconstrictor Response ◽  
Body Cooling ◽  
Whole Body Cooling

Previous work showed that local cooling (LC) attenuates the vasoconstrictor response to whole body cooling (WBC). We tested the extent to which this attenuation was due to the decreased baseline skin blood flow following LC. In eight subjects, skin blood flow was assessed using laser-Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC) was expressed as LDF divided by blood pressure. Subjects were dressed in water-perfused suits to control WBC. Four forearm sites were prepared with microdialysis fibers, local heating/cooling probe holders, and laser-Doppler probes. Three sites were locally cooled from 34 to 28°C, reducing CVC to 45.9 ± 3.9, 42 ± 3.9, and 44.5 ± 4.8% of baseline ( P < 0.05 vs. baseline; P > 0.05 among sites). At two sites, CVC was restored to precooling baseline levels with sodium nitroprusside (SNP) or isoproterenol (Iso), increasing CVC to 106.4 ± 12.4 and 98.9 ± 10.1% of baseline, respectively ( P > 0.05 vs. precooling). Whole body skin temperature, apart from the area of blood flow measurement, was reduced from 34 to 31°C. Relative to the original baseline, CVC decreased ( P < 0.05) by 44.9 ± 2.8 (control), 11.3 ± 2.4 (LC only), 29 ± 3.7 (SNP), and 45.8 ± 8.7% (Iso). The reductions at LC only and SNP sites were less than at control or Iso sites ( P < 0.05); the responses at those latter sites were not different ( P > 0.05), suggesting that the baseline change in CVC with LC is important in the attenuation of reflex vasoconstrictor responses to WBC.

scholarly journals Cutaneous vasomotor responses in boys and men

2018 ◽  
Vol 43 (10) ◽  
pp. 1019-1026 ◽  
Author(s):  
Gary J. Hodges ◽  
Matthew C. Mueller ◽  
Stephen S. Cheung ◽  
Bareket Falk
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Local Heating ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Local Skin ◽  
Doppler Flowmetry ◽  
Age Related ◽  
Isometric Handgrip Exercise ◽  
Underlying Mechanisms

Few studies have investigated skin blood flow in children and age-related differences in the underlying mechanisms. We examined mechanisms of skin blood flow responses to local heating, postocclusive reactive hyperaemia (PORH), and isometric handgrip exercise in adult and prepubescent males, hypothesizing that skin blood flow responses would be greater in children compared with adults. We measured skin blood flow in 12 boys (age, 9 ± 1 years) and 12 men (age, 21 ± 1 years) using laser-Doppler flowmetry at rest, in response to 3-min PORH, 2-min isometric handgrip exercise, and local skin heating to 39 °C (submaximal) and 44 °C (maximal). Using wavelet analysis we assessed endothelial, neural, and myogenic activities. At rest and in response to local heating to 39 °C, children had higher skin blood flow and endothelial activity compared with men (d ≥ 1.1, p < 0.001) and similar neurogenic and myogenic activities (d < 0.2, p > 0.05). Maximal responses to 44 °C local skin heating, PORH, and isometric handgrip exercise did not differ between boys and men (all d ≤ 0.2, p > 0.05). During PORH children demonstrated greater endothelial activity compared with men (d ≥ 0.6, p < 0.05); in contrast, men had higher neurogenic activity (d = 1.0, p < 0.01). During isometric handgrip exercise there were no differences in endothelial, neurogenic, and myogenic activities (d < 0.2, p > 0.3), with boys and men demonstrating similar increases in endothelial activity and decreases in myogenic activity (d ≥ 0.8, p < 0.05). These data suggest that boys experience greater levels of skin blood flow at rest and in response to submaximal local heating compared with men, while maximal responses appear to be similar. Additionally, endothelial mediators seem to contribute more to vasodilatation in boys than in men.

Skin blood flow and sweating changes following exercise training and heat acclimation

1977 ◽  
Vol 43 (1) ◽  
pp. 133-137 ◽  
Author(s):  
M. F. Roberts ◽  
C. B. Wenger ◽  
J. A. Stolwijk ◽  
E. R. Nadel
Keyword(s):  
Blood Flow ◽  
Exercise Training ◽  
Forearm Blood Flow ◽  
Sweat Rate ◽  
Heat Acclimation ◽  
Lower Body ◽  
Body Temperatures ◽  
Internal Temperature ◽  
Exercise Training Program ◽  
Lower Blood

Eight subjects underwent an exercise training program (10 days at 75% VO2max for 1 h/day at 25 degrees C db/13 degrees C wb) and a heat-acclimation program (10 days at 50% VO2max for 1 h/day at 35 degrees C db/32 degrees C wb). The relations of chest sweat rate and of forearm blood flow to internal temperature were determined for each subject at a 25 degrees C ambient temperature before training, between training and acclimation, and following acclimation. Training shifted the vasodilation and sweating thresholds toward lower internal temperatures, and acclimation further lowered these thresholds. All threshold shifts were statistically significant (P less than 0.05). Training and acclimation both appeared to increase the slope of the sweating relation, but these effects were not statistically significant. Changes in the slope of the blood flow relation were small and inconsistent. Since arm blood flow is higher at any given internal temperature after acclimation, the lower blood flow which is reported to accompany heat acclimation must result from the lower body temperatures.

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