Effect of heat stress on cutaneous vascular responses to the initiation of exercise

1982 ◽  
Vol 53 (3) ◽  
pp. 744-749 ◽  
Author(s):  
J. M. Johnson ◽  
M. K. Park
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Skin Temperature ◽  
Skin Blood Flow ◽  
Forearm Blood Flow ◽  
Moderate Intensity ◽  
Internal Temperature ◽  
Vascular Responses ◽  
Vasoconstrictor Response ◽  
Leg Exercise

To explore further the competition between vasoconstrictor and vasodilator reflexes in the regulation of skin blood flow, responses in forearm blood flow (FBF) to the initiation of supine leg exercise were measured by plethysmography against a background of rising internal temperature. In 17 studies involving six men, skin temperature (Tsk) was controlled with water-perfused suits first at normothermic levels, followed by a 40- to 50-min period during which Tsk was held at 3813;38.5 degrees C. Supine leg exercise at a moderate intensity (100–150 W) was performed for 5–6 min of each 15 min throughout, yielding one period of exercise performed during normothermic conditions and three periods of exercise performed during the period of elevated Tsk. On the average, FBF fell significantly with the beginning of each period of exercise (P less than 0.05). Furthermore, the amount by which FBF fell tended to increase with increasing levels of preexercise FBF. Thus the average fall in FBF associated with the onset of the last period of exercise, 2.45 ml X 100 ml-1 X min-1, significantly exceeded the 1.12 ml X 100 ml-1 X min-1 fall in FBF seen with onset of work in normothermic conditions. These responses were not due to changes in internal temperature as reflected by esophageal temperatures. However, individual studies occasionally revealed a reduction or abolition of the vasoconstrictor response with the last period of exercise. These findings are in agreement with earlier studies showing a cutaneous participation in the vasoconstrictor responses to exercise but also indicate that sufficient hyperthermia can attenuate or even abolish this response.

Forearm blood flow during body temperature transients produced by leg exercise

1975 ◽  
Vol 38 (1) ◽  
pp. 58-63 ◽  
Author(s):  
C. B. Wenger ◽  
M. F. Roberts ◽  
J. A. Stolwijk ◽  
E. R. Nadel
Keyword(s):  
Blood Flow ◽  
Skin Temperature ◽  
Forearm Blood Flow ◽  
Bicycle Ergometer ◽  
Vapor Pressures ◽  
Internal Temperature ◽  
Ambient Temperatures ◽  
Forearm Skin ◽  
Leg Exercise ◽  
Skin Temperatures

Subjects exercised for 30 min on a bicycle ergometer at 30, 50, and 70% of maximal aerobic power in ambient temperatures of 15, 25, and 35 degrees C and vapor pressures of less than 18 Torr. Exercise was used to vary internal temperature during an experiment, and different ambient temperatures were used to vary skin temperatures independently of internal temperature. Forearm skin temperature was fixed at about 36.5 degrees C. Esophageal temperature (Tes) was measured with a thermocouple at the level of the left atrium, and mean skin temperature (Tsk) was calculated from a weighted mean of thermocouple temperatures at eight skin sites. Forearm blood flow (BF) was measured by electrocapacitance plethysmography. Our data are well accounted for by an equation of the form BF = a1Tes + q2Tsk + b, independent of exercise intensity, although some subjects showed an equivocal vasodilator effect of exercise. The ratios a1/a2 (7.5, 9.6, 11.7) are quite similar to the ratios (8.6, 10.4) of the corresponding coefficients in two recent models of thermoregulatory sweating.

Interactions between local and reflex influences on human forearm skin blood flow

1976 ◽  
Vol 41 (6) ◽  
pp. 826-831 ◽  
Author(s):  
J. M. Johnson ◽  
G. L. Brengelmann ◽  
L. B. Rowell
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Forearm Blood Flow ◽  
Lower Body Negative Pressure ◽  
Muscle Blood Flow ◽  
Whole Body ◽  
Vasoconstrictor Response ◽  
Human Forearm ◽  
Forearm Skin ◽  
Forearm Muscle

A three-part experiment was designed to examine interactions between local and reflex influences on forearm skin blood flow (SkBF). In part I locally increasing arm skin temperature (Tsk) to 42.5 degrees C was not associated with increases in underlying forearm muscle blood flow, esophageal temperature (Tes), or forearm blood flow in the contralateral cool arm. In part II whole-body Tsk was held at 38 or 40 degrees C and the surface temperature of one arm held at 38 or 42 degrees C for prolonged periods. SkBF in the heated arm rose rapidly with the elevation in body Tsk and arm Tsk continued to rise as Tes rose. SkBF in the arm kept at 32 degrees C paralleled rising Tes. In six studies, SkBF in the cool arm ultimately converged with SkBF in the heated arm. In eight other studies, heated arm SkBF maintained an offset above cool arm SkBF throughout the period of whole-body heating. In part III, local arm Tsk of 42.5 degrees C did not abolish skin vasoconstrictor response to lower body negative pressure. We conclude that local and reflex influences to skin interact so as to modify the degree but not the pattern of skin vasomotor response.

Effects of caffeine on blood pressure, heart rate, and forearm blood flow during dynamic leg exercise

1998 ◽  
Vol 85 (1) ◽  
pp. 154-159 ◽  
Author(s):  
Jason W. Daniels ◽  
Paul A. Molé ◽  
James D. Shaffrath ◽  
Charles L. Stebbins
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Systolic Blood Pressure ◽  
Skin Temperature ◽  
Rectal Temperature ◽  
Forearm Blood Flow ◽  
Dynamic Exercise ◽  
Ang Ii ◽  
Leg Exercise

This study examined the acute effects of caffeine on the cardiovascular system during dynamic leg exercise. Ten trained, caffeine-naive cyclists (7 women and 3 men) were studied at rest and during bicycle ergometry before and after the ingestion of 6 mg/kg caffeine or 6 mg/kg fructose (placebo) with 250 ml of water. After consumption of caffeine or placebo, subjects either rested for 100 min (rest protocol) or rested for 45 min followed by 55 min of cycle ergometry at 65% of maximal oxygen consumption (exercise protocol). Measurement of mean arterial pressure (MAP), forearm blood flow (FBF), heart rate, skin temperature, and rectal temperature and calculation of forearm vascular conductance (FVC) were made at baseline and at 20-min intervals. Plasma ANG II was measured at baseline and at 60 min postingestion in the two exercise protocols. Before exercise, caffeine increased both systolic blood pressure (17%) and MAP (11%) without affecting FBF or FVC. During dynamic exercise, caffeine attenuated the increase in FBF (53%) and FVC (50%) and accentuated exercise-induced increases in ANG II (44%). Systolic blood pressure and MAP were also higher during exercise plus caffeine; however, these increases were secondary to the effects of caffeine on resting blood pressure. No significant differences were observed in heart rate, skin temperature, or rectal temperature. These findings indicate that caffeine can alter the cardiovascular response to dynamic exercise in a manner that may modify regional blood flow and conductance.

Age alters regional distribution of blood flow during moderate-intensity exercise

1995 ◽  
Vol 79 (4) ◽  
pp. 1112-1119 ◽  
Author(s):  
W. L. Kenney ◽  
C. W. Ho
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Renal Blood Flow ◽  
Skin Blood Flow ◽  
Forearm Blood Flow ◽  
Regional Distribution ◽  
Splanchnic Blood Flow ◽  
Moderate Intensity ◽  
Plasma Norepinephrine ◽  
Moderate Intensity Exercise

During dynamic exercise in warm environments, requisite increases in skin and active muscle blood flows are supported by increasing cardiac output (Qc) and redistributing flow away from splanchnic and renal circulations. To examine the effect of age on these responses, six young (Y; 26 +/- 2 yr) and six older (O; 64 +/- 2 yr) men performed upright cycle exercise at 35 and 60% of peak O2 consumption (VO2peak) in 22 and 36 degrees C environments. To further isolate age, the two age groups were closely matched for VO2peak, weight, surface area, and body composition. Measurements included heart rate, Qc (CO2 rebreathing), skin blood flow (from increases in forearm blood flow (venous occlusion plethysmography), splanchnic blood flow (indocyanine green dilution), renal blood flow (p-amino-hippurate clearance), and plasma norepinephrine concentration. There were no significant age differences in Qc; however, in both environments the O group maintained Qc at a higher stroke volume and lower heart rate. At 60% VO2peak, forearm blood flow was significantly lower in the O subjects in each environment. Splanchnic blood flow fell (by 12–14% in both groups) at the lower intensity, then decreased to a greater extent at 60% VO2peak in Y than in O subjects (e.g., -45 +/- 2 vs. -33 +/- 3% for the hot environment, P < 0.01). Renal blood flow was lower at rest in the O group, remained relatively constant at 35% VO2peak, then decreased by 20–25% in both groups at 60% VO2peak. At 60% VO2peak, 27 and 37% more total blood flow was redistributed away from these two circulations in the Y than in the O group at 22 and 36 degrees, respectively. It was concluded that the greater increase in skin blood flow in Y subjects is partially supported by a greater redistribution of blood flow away from splanchnic and renal vascular beds.

Active cutaneous vasodilation in resting humans during mild heat stress

2005 ◽  
Vol 98 (3) ◽  
pp. 829-837 ◽  
Author(s):  
Yoshi-Ichiro Kamijo ◽  
Kichang Lee ◽  
Gary W. Mack
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Skin Temperature ◽  
Skin Blood Flow ◽  
Sweat Rate ◽  
Mean Skin Temperature ◽  
Local Skin ◽  
Mild Heat ◽  
Normal Core ◽  
Local Sweat Rate

The role of skin temperature in reflex control of the active cutaneous vasodilator system was examined in six subjects during mild graded heat stress imposed by perfusing water at 34, 36, 38, and 40°C through a tube-lined garment. Skin sympathetic nerve activity (SSNA) was recorded from the peroneal nerve with microneurography. While monitoring esophageal, mean skin, and local skin temperatures, we recorded skin blood flow at bretylium-treated and untreated skin sites by using laser-Doppler velocimetry and local sweat rate by using capacitance hygrometry on the dorsal foot. Cutaneous vascular conductance (CVC) was calculated by dividing skin blood flow by mean arterial pressure. Mild heat stress increased mean skin temperature by 0.2 or 0.3°C every stage, but esophageal and local skin temperature did not change during the first three stages. CVC at the bretylium tosylate-treated site (CVCBT) and sweat expulsion number increased at 38 and 40°C compared with 34°C ( P < 0.05); however, CVC at the untreated site did not change. SSNA increased at 40°C ( P < 0.05, different from 34°C). However, SSNA burst amplitude increased ( P < 0.05), whereas SSNA burst duration decreased ( P < 0.05), at the same time as we observed the increase in CVCBT and sweat expulsion number. These data support the hypothesis that the active vasodilator system is activated by changes in mean skin temperature, even at normal core temperature, and illustrate the intricate competition between active vasodilator and the vasoconstrictor system for control of skin blood flow during mild heat stress.

Reflex control of skin blood flow by skin temperature: role of core temperature

1979 ◽  
Vol 47 (6) ◽  
pp. 1188-1193 ◽  
Author(s):  
J. M. Johnson ◽  
M. K. Park
Keyword(s):  
Blood Flow ◽  
Skin Temperature ◽  
Skin Blood Flow ◽  
Work Load ◽  
Reflex Response ◽  
Esophageal Temperature ◽  
Internal Temperature ◽  
Reflex Control ◽  
Different Levels

Two protocols were used to discover whether the reflex response in skin blood flow (SkBF) to rising skin temperature (Tsk) was dependent on the level of internal temperature. Part I. In five subjects, Tsk (controlled with water-perfused suits) was raised to 37 degrees C prior to, between 2 and 5 min, or between 10 and 17 min of exercise. The associated SkBF elevation per degree rise in Tsk averaged 0.20, 1.28, and 1.75 ml/100 ml . min, respectively. When Tsk was raised during the first 5 min of exercise, esophageal temperature (Tes) rose markedly (0.39 degrees C), but transiently fell if Tsk was raised after 10 min of exercise. Part II. In six subjects, different work loads were used to develop different levels of internal temperature. Tsk was elevated to 37 degrees C after 10--15 min at light (50--75 W) or moderate (100--150 W) work loads. At the heavier work load (and higher Tes), the rise in forearm SkBF per degree rise in Tsk averaged 2.33 +/- 0.38 (SE) times that observed at the light work load. These data strongly suggest that the reflex response of SkBF to rising Tsk is dependent on the level of internal temperature.

Aging and the skin blood flow response to the unloading of baroreceptors during heat and cold stress

2004 ◽  
Vol 96 (3) ◽  
pp. 1019-1025 ◽  
Author(s):  
Glaucio Scremin ◽  
W. Larry Kenney
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Cold Stress ◽  
Skin Blood Flow ◽  
Forearm Blood Flow ◽  
Lower Body Negative Pressure ◽  
Older Men ◽  
Stress Conditions ◽  
Vascular Conductance ◽  
Heat And Cold Stress

Control of skin blood flow (SkBF) is on the efferent arm of both thermoregulatory and nonthermoregulatory reflexes. To what extent aging may affect the SkBF response when these two reflex systems interact is unknown. To determine the response of aged skin to the unloading of baroreceptors in thermoneutral, cold stress, and heat stress conditions, sequential bouts of nonhypotensive lower body negative pressure (LBNP) were applied at -10, -20, and -30 mmHg in 14 young (18–25 yr) and 14 older (63–78 yr) men. SkBF was measured by laser-Doppler velocimetry (averaged over 2 forearm sites), and data are expressed as percentage of maximal cutaneous vascular conductance (%CVCmax). Total forearm blood flow was measured by venous occlusion plethysmography, and forearm vascular conductance (FVC) was calculated as the ratio of forearm blood flow to mean arterial pressure. In young men, all three intensities of LBNP in thermoneutrality decreased FVC significantly ( P < 0.05), but FVC at -10 mmHg did not change in the older men. There were no significant LBNP effects on %CVCmax. Application of LBNP during cold stress did not significantly change %CVCmax or FVC in either age group. During heat stress, -10 to -30 mmHg of LBNP decreased FVC significantly ( P < 0.05) in both age groups, but these decreases were attenuated in the older men ( P < 0.05). %CVCmax decreased at -30 mmHg in the younger men only. These results suggest that older men have an attenuated skin vasoconstrictor response to the unloading of baroreceptors in heat stress conditions. Furthermore, the forearm vasoconstriction elicited by LBNP in older men reflects that of underlying tissue (i.e., muscle) rather than that of skin, whereas -30 mmHg LBNP also decreases SkBF in young hyperthermic men.

Thermoregulatory reflexes and cutaneous active vasodilation during heat stress in hypertensive humans

1998 ◽  
Vol 85 (1) ◽  
pp. 175-180 ◽  
Author(s):  
D. L. Kellogg ◽  
S. R. Morris ◽  
S. B. Rodriguez ◽  
Y. Liu ◽  
M. Grossmann ◽  
...  
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Skin Blood Flow ◽  
Forearm Blood Flow ◽  
Venous Occlusion ◽  
Vascular Conductance ◽  
Doppler Flowmetry ◽  
Forearm Vascular Conductance ◽  
Normotensive Subjects ◽  
Cutaneous Vascular Conductance

During dynamic exercise in the heat, increases in skin blood flow are attenuated in hypertensive subjects when compared with normotensive subjects. We studied responses to passive heat stress (water-perfused suits) in eight hypertensive and eight normotensive subjects. Forearm blood flow was measured by venous-occlusion plethysmography, mean arterial pressure (MAP) was measured by Finapres, and forearm vascular conductance (FVC) was calculated. Bretylium tosylate (BT) iontophoresis was used to block active vasoconstriction in a small area of skin. Skin blood flow was indexed by laser-Doppler flowmetry at BT-treated and untreated sites, and cutaneous vascular conductance was calculated. In normothermia, FVC was lower in hypertensive than in normotensive subjects ( P < 0.01). During heat stress, FVC rose to similar levels in both groups ( P > 0.80); concurrent cutaneous vascular conductance increases were unaffected by BT treatment ( P > 0.60). MAP was greater in hypertensive than in normotensive subjects during normothermia ( P < 0.05, hypertensive vs. normotensive subjects). During hyperthermia, MAP fell in hypertensive subjects but showed no statistically significant change in normotensive subjects ( P < 0.05, hypertensive vs. normotensive subjects). The internal temperature at which vasodilation began did not differ between groups ( P> 0.80). FVC is reduced during normothermia in unmedicated hypertensive subjects; however, they respond to passive heat stress in a fashion no different from normotensive subjects.

Interaction of local and reflex thermal effects in control of forearm blood flow

1985 ◽  
Vol 58 (1) ◽  
pp. 251-257 ◽  
Author(s):  
C. B. Wenger ◽  
R. B. Bailey ◽  
M. F. Roberts ◽  
E. R. Nadel
Keyword(s):  
Blood Flow ◽  
Ambient Temperature ◽  
Skin Temperature ◽  
Thermal Effects ◽  
Forearm Blood Flow ◽  
Local Heating ◽  
The Other ◽  
Leg Exercise

We measured forearm blood flow (ABF) bilaterally on six subjects during 15-min periods of leg exercise and the first 10 min of recovery. One forearm (control) was kept at about 33 degrees C skin temperature in all experiments. In experiments at ambient temperature (Ta) of 15 degrees C, the other arm (experimental) was kept at about 26, 33, and 40 degrees C, respectively, during three successive cycles of exercise and recovery. ABF in the 26 degrees C forearm was linearly related to and averaged 42% of control. The relation of ABF in the 40 degrees C forearm to control ABF showed a bend at control ABF of 4–5 ml X 100 ml-1 X min-1. Below the bend, experimental ABF average 213% of control. Above the bend, experimental ABF averaged 5.09 ml X 100 ml-1 X min-1 above control. In four subjects, after heating the experimental forearm to 40 degrees C, we measured ABF for 25–30 min at rest in Ta of both 15 and 25 degrees C. At 25 degrees C Ta, ABF in the heated forearms rose gradually, but control ABF showed little change. At 15 degrees C Ta, the effect on ABF of local heating to 40 degrees C was much reduced, apparently due to reflex vasoconstrictor signals.

Altered control of skin blood flow at high skin and core temperatures

1975 ◽  
Vol 38 (5) ◽  
pp. 839-845 ◽  
Author(s):  
C. R. Wyss ◽  
G. L. Brengelmann ◽  
J. M. Johnson ◽  
L. B. Rowell ◽  
D. Silverstein
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Skin Temperature ◽  
Linear Model ◽  
Skin Blood Flow ◽  
Forearm Blood Flow ◽  
Right Atrial ◽  
Esophageal Temperature ◽  
Cooling Period ◽  
Blood Temperature

Five subjects were studied during periods of controlled increases and decreases in skin temperature (Ts) over the Ts range of 34–40 degrees C. One protocol was designed to observe changes in forearm blood flow (FBF) and heart rate (HR) with changes in core temperature (Tc; right atrial blood temperature and esophageal temperature were measured) with Ts held constant at two levels. FBF and HR changed linearly with Tc in the Tc range of 37–38 degrees C with Ts constant at 38 degrees C. A second protocol imposed Ts changes at two levels of Ts and Tc; this protocol also included a prolonged cooling period. The influence of Ts on FBF and HR was reduced when Ts changes occurred at an elevated Ts and Tc, and FBF showed considerable hysteresis during cooling. We conclude that a linear model for the control of FBF or HR is inadequate as a tool for predicting the control of these variables.

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