Effect of mild essential hypertension on control of forearm blood flow during exercise in the heat

Six essential hypertensive (resting mean arterial pressure, MAP greater than 110 mmHg) and eight normotensive (resting MAP less than 95 mmHg) men, aged 30–58 yr, were tested during 1 h of dynamic leg exercise in the heat. Environmental conditions were fixed at 38 degrees C dry-bulb temperature and 28 degrees C wet-bulb temperature; exercise intensity was preset to approximate 40% of each subject's maximal aerobic capacity (actual range 38–43%). Forearm blood flow (FBF) was measured by impedance plethysmography. The intergroup difference in arterial pressure was maintained but not increased or decreased during exercise in the heat. FBF increased in both groups, but the increase was significantly less for the hypertensive subjects. FBF showed a significant linear correlation (different from 0) with core temperature in seven of eight control subjects but in none of the hypertensive subjects. The magnitude of FBF increase was inversely proportional to resting MAP (r = -0.89). It was concluded that essential hypertensive subjects respond to exercise in the heat with a diminished FBF response related to an alteration in control relative to central (core temperature) influences. This may be due to an imbalance between thermal and nonthermal (baroreflex) mechanisms controlling cutaneous blood flow.

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Effect of Changes in Ventricular Rate on Forearm Blood Flow and Systemic Arterial Pressure in Patients with Artificial Pacemakers

Scandinavian Journal of Clinical and Laboratory Investigation ◽

10.3109/00365517309082467 ◽

1973 ◽

Vol 32 (3) ◽

pp. 245-250 ◽

Cited By ~ 1

Author(s):

S. Bevegård ◽

I. Karlöf ◽

L. Resnekov

Keyword(s):

Blood Flow ◽

Arterial Pressure ◽

Forearm Blood Flow ◽

Systemic Arterial Pressure ◽

Ventricular Rate

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734 FOREARM BLOOD FLOW RESPONSE TO A STEP INCREASE IN COMBINED FOREARM AND LEG EXERCISE

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-199405001-00736 ◽

1994 ◽

Vol 26 (Supplement) ◽

pp. S131

Author(s):

M. E. Tschakovsky ◽

R. L. Hughson

Keyword(s):

Blood Flow ◽

Forearm Blood Flow ◽

Blood Flow Response ◽

Flow Response ◽

Leg Exercise

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

Journal of Applied Physiology ◽

10.1152/jappl.1998.85.1.154 ◽

1998 ◽

Vol 85 (1) ◽

pp. 154-159 ◽

Cited By ~ 66

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.

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Cutaneous blood flow during exercise is higher in endurance-trained humans

Journal of Applied Physiology ◽

10.1152/jappl.2000.88.2.738 ◽

2000 ◽

Vol 88 (2) ◽

pp. 738-744 ◽

Cited By ~ 56

Author(s):

Ricardo G. Fritzsche ◽

Edward F. Coyle

Keyword(s):

Blood Flow ◽

Oxygen Uptake ◽

Forearm Blood Flow ◽

Peak Oxygen Uptake ◽

Metabolic Rates ◽

Esophageal Temperature ◽

Cutaneous Blood Flow ◽

Cycling Exercise ◽

C 50 ◽

Cutaneous Blood

This study determined whether cutaneous blood flow during exercise is different in endurance-trained (Tr) compared with untrained (Untr) subjects. Ten Tr and ten Untr men (62.4 ± 1.7 and 44.2 ± 1.8 ml ⋅ kg− 1 ⋅ min− 1, respectively; P < 0.05) underwent three 20-min cycling-exercise bouts at 50, 70, and 90% peak oxygen uptake in this order, with 30 min rest in between. The environmental conditions were neutral (∼23–24°C, 50% relative humidity, front and back fans at 2.5 m/s). Because of technical difficulties, only seven Tr and seven Untr subjects completed all forearm blood flow and laser-Doppler cutaneous blood flow (CBF) measurements. Albeit similar at rest, at the end of all three exercise bouts, forearm blood flow was ∼40% higher in Tr compared with Untr subjects (50%: 4.64 ± 0.50 vs. 3.17 ± 0.20, 70%: 6.17 ± 0.61 vs. 4.41 ± 0.37, 90%: 6.77 ± 0.62 vs. 5.01 ± 0.37 ml ⋅ 100 ml− 1 ⋅ min− 1, respectively; n = 7; all P < 0.05). CBF was also higher in Tr compared with Untr subjects at all relative intensities ( n = 7; all P < 0.05). However, esophageal temperature was not different in Tr compared with Untr subjects at the end of any of the aforementioned exercise bouts (50%: 37.8 ± 0.1 vs. 37.9 ± 0.1°C, 70%: 38.1 ± 0.1 vs. 38.1 ± 0.1°C, and 90%: 38.8 ± 0.1 vs. 38.6 ± 0.1°C, respectively). We conclude that a higher CBF may allow Tr subjects to achieve an esophageal temperature similar to that of Untr, despite their higher metabolic rates and thus higher heat production rates, during exercise at 50–90% peak oxygen uptake.

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Circadian rhythm in sweating and cutaneous blood flow

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1984.246.3.r321 ◽

1984 ◽

Vol 246 (3) ◽

pp. R321-R324 ◽

Cited By ~ 20

Author(s):

L. A. Stephenson ◽

C. B. Wenger ◽

B. H. O'Donovan ◽

E. R. Nadel

Keyword(s):

Blood Flow ◽

Circadian Rhythm ◽

Body Temperature ◽

Forearm Blood Flow ◽

Sweat Rate ◽

Circadian Variation ◽

Esophageal Temperature ◽

Cutaneous Blood Flow ◽

Cutaneous Vasodilation ◽

Cutaneous Blood

To characterize the changes in the control of the heat loss responses associated with the circadian variation in body temperature, we studied five men during 20 min of exercise in 25 degrees C on 6 separate days. Experiments were conducted at six times, equally spaced over the 24-h day. Esophageal temperature (Tes) and chest sweat rate (msw) were measured continuously, and forearm blood flow (FBF) was measured one to two times per minute. The thresholds for sweating and forearm vasodilation were significantly higher at 1600 and 2000 than at 2400 and 0400, averaging 0.57 and 0.65 degrees C higher, respectively, at 1600 than at 0400. Resting Tes and the Tes thresholds for cutaneous vasodilation and sweating during exercise all showed a similar circadian rhythm. The level at which core temperature is regulated therefore varies over the 24-h day with the zenith occurring around 1600 and the nadir at 0400. However, whereas the slope of the msw-to-Tes relation did not change over the 24-h day, the slope of the FBF-to-Tes relation tended to increase between 0400 and 2400, implying that the circadian rhythm may be more complex than just a shift in the central reference temperature.

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Failure of impedance plethysmography to follow exercise-induced changes in limb blood flow

Clinical Science ◽

10.1042/cs0750041 ◽

1988 ◽

Vol 75 (1) ◽

pp. 41-46 ◽

Cited By ~ 2

Author(s):

Richard L. Hughson

Keyword(s):

Blood Flow ◽

Supine Position ◽

Venous Occlusion ◽

Impedance Plethysmography ◽

Electrode Position ◽

Limb Blood Flow ◽

Mean Values ◽

Leg Exercise ◽

Exercise Induced ◽

Induced Changes

1. The blood flow in the forearm and the calf of six healthy volunteers was measured at rest and after exercise by impedance plethysmography using pulsatile (QZp) and venous occlusion (QZocc) methods, and by venous occlusion strain gauge plethysmography (Qsg). 2. At rest, the impedance QZp method gave values slightly higher than those of Qsg. In the forearm, the ratio QZp to Qsg was 1.26 in the supine position and 1.97 in the upright sitting position. For the calf muscle, the ratios were 1.08 in the supine position and 1.23 in the upright position. 3. Immediately after exercise, Qsg increased from resting values of approximately 2–4 ml min−1 100 ml−1 to mean values of 16–25 ml min−1 100 ml−1 in upright and supine arm or leg exercise. In contrast, the QZp values after exercise increased to only 3.1–4.6 ml min−1 100 ml−1. QZocc likewise failed to show increases in flow except in the supine leg exercise, where flow increased to 8.7 ml min−1 100 ml−1. 4. In an additional subject, it was shown that electrode position had no significant effect on the QZp blood flow measurement after exercise. 5. The failure of QZp to accurately follow the change in Qsg with exercise was probably due in part to pulsatile venous outflow. In addition, changes in microvessel packed cell volume and shear rate may influence the observed QZp. It is concluded that impedance plethysmography is not valid for estimation of limb blood flow during reactive hyperaemia after exercise.

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Forehead Cutaneous Blood Flow in Response to Unloaded Kaatsu Leg Exercise

Medicine & Science in Sports & Exercise ◽

10.1249/01.mss.0000274683.37931.b5 ◽

2007 ◽

Vol 39 (Supplement) ◽

pp. S426

Author(s):

Keiko Kusuhara ◽

Taku Fujita ◽

Tomohiro Yasuda ◽

Toshiaki Nakajima ◽

Yoshiaki Sato ◽

...

Keyword(s):

Blood Flow ◽

Cutaneous Blood Flow ◽

Leg Exercise ◽

Cutaneous Blood

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The Effect of a 48h Fast on the Thermoregulatory Responses to Graded Cooling in Man

Clinical Science ◽

10.1042/cs0670445 ◽

1984 ◽

Vol 67 (4) ◽

pp. 445-452 ◽

Cited By ~ 15

Author(s):

I. A. MacDonald ◽

T. Bennett ◽

R. Sainsbury

Keyword(s):

Blood Flow ◽

Metabolic Rate ◽

Core Temperature ◽

Forearm Blood Flow ◽

Nervous Activity ◽

Sympathetic Nervous Activity ◽

Noradrenaline Level ◽

Thermoregulatory Responses ◽

Autonomic Reflex ◽

Male Subjects

1. The thermoregulatory responses to graded cooling were measured in 11 healthy male subjects after a 12 h fast and after a 48 h fast. The cooling stimulus was produced by changing the temperature of the skin of the trunk and legs with a water-perfused suit. Five levels of skin temperature from 35.5 to 24°C were applied on each occasion. 2. After a 12 h fast, core temperature was maintained during cooling. This maintenance of core temperature was associated with an increase in metabolic rate and a reduction in blood flow to the hand and to the forearm. 3. After 48 h of fasting, the subjects could not maintain core temperature during cooling, and a decrease of 0.36 ± 0.05°C occurred as the suit temperature was reduced from 35.9 to 24°C. Metabolic rate was slightly higher after the 48 h fast than after the 12 h fast, but similar increases in metabolic rate were observed during cooling. 4. Vasoconstriction in the hand was initially less after a 48 h fast than after a 12 h fast, but at the lowest suit temperature, hand blood flow was similar, and low, on both occasions. After 48 h of fasting, forearm blood flow was elevated at all suit temperatures, being approximately twice the level recorded after the 12 h fast. 5. Venous plasma noradrenaline levels did not change during cooling after the 12 h fast, whilst after 48 h of fasting a significant increase in noradrenaline level was observed at the lowest suit temperature. 6. The results of this study provide further evidence that fasting induces an impairment of autonomic reflex mechanisms, but it is not clear whether this is due to a suppression of sympathetic nervous activity.

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Forearm blood flow during body temperature transients produced by leg exercise

Journal of Applied Physiology ◽

10.1152/jappl.1975.38.1.58 ◽

1975 ◽

Vol 38 (1) ◽

pp. 58-63 ◽

Cited By ~ 98

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.

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