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.

Thermoregulatory control of finger blood flow

1975 ◽  
Vol 38 (6) ◽  
pp. 1078-1082 ◽  
Author(s):  
C. B. Wenger ◽  
M. F. Roberts ◽  
E. R. Nadel ◽  
J. A. Stolwijk
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Aerobic Power ◽  
Water Vapor Pressure ◽  
Bicycle Ergometer ◽  
Finger Blood Flow ◽  
Internal Temperature ◽  
Finger Temperature ◽  
Ambient Temperatures ◽  
Skin Temperatures

Three men exercised on a bicycle ergometer at 30, 50, asd 70 per cent of maximal aerobic power in ambient temperatures of 15, 25, and 35 degrees C with water vapor pressure less than 18 Torr. Exercies was used to vary internal temperature during as experiment, and different ambient temperatures were used to vary skin temperatures independently of internal temperature. Finger temperature was fixed at about 35.7 degrees C. Espohageal temperature (Tes) was measured with a thermocouple at the level of the left atrium, and mean skin temperature (Tsk) was calcualted from a weighted mean of thermocouple temperatures at eight skin sites. Finger blood flow (BF) was measured by electrocapacitance plethysmography. Although some subjects showed small and equivocal vasomotor effects of exercise, our data are well accounted for by an equation of the form BF equal to alTes + a2Tsk + b, independent of exercise intensity. For these subjects, the ratios a1/a2 (5.9, 8.6, 9.4) were similar to the ratios of the corresponding coefficients recently reported for thermaoregulatory sweating (8.6, 10.4) and for forearm blood flow (9.6).

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.

Responses of forearm blood flow to graded leg exercise in man

1979 ◽  
Vol 46 (3) ◽  
pp. 457-462 ◽  
Author(s):  
J. M. Johnson
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Linear Regression Analysis ◽  
Work Load ◽  
Multiple Linear Regression Analysis ◽  
Internal Temperature ◽  
The Third ◽  
Graded Response ◽  
Forearm Skin ◽  
Leg Exercise

To test whether the cutaneous vascular responses to exercise are influenced by the level of work, three strategies were followed. In each, forearm blood flow and esophageal temperature were measured throughout. In part I, the forearm blood flow-internal temperature relationships from separate sessions of steady-state exercise at different loads were compared. In part II, work load was varied between 50 and 150 W. Work load was raised or lowered 50 W every 5 min over 60–75 min. The third strategy was to examine the immediate change in forearm blood flow accompanying rapid, large increments or decrements in work load. The results do not support a graded response of the cutaneous circulation to exercise. In both the first and second protocols above, the relationship of forearm blood flow to internal temperature was not measurably altered by work load. Multiple linear regression analysis failed to reveal a consistent role for work load in part II. In the third protocol, there was no consistent or sustained response to an abrupt change in work load. Thus over the range of work loads used in this study there appears to be no major role for the level of work in the regulation of forearm skin blood flow other than through the effect on internal temperature.

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.

Mechanisms of control of skin blood flow during prolonged exercise in humans

1993 ◽  
Vol 265 (2) ◽  
pp. H562-H568 ◽  
Author(s):  
D. L. Kellogg ◽  
J. M. Johnson ◽  
W. L. Kenney ◽  
P. E. Pergola ◽  
W. A. Kosiba
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Sweat Rate ◽  
Bicycle Ergometer ◽  
Dew Point ◽  
Whole Body ◽  
Internal Temperature ◽  
Vasodilator Activity ◽  
Forearm Skin ◽  
Reduced Rate

Exercise in a warm environment raises internal temperature and leads to a rapid increase in skin blood flow (SkBF). As exercise continues, and internal temperature approaches 38 degrees C, the rate of rise of SkBF is markedly attenuated despite further significant increases in internal temperature. To find whether this attenuation is mediated by increased cutaneous active vasoconstrictor activity or by a reduced rate of rise of active vasodilator activity, each of 12 male subjects had 0.64 cm2 forearm skin sites iontophoretically treated with bretylium tosylate for selective local blockade of noradrenergic vasoconstrictor nerves. SkBF was monitored there and at adjacent untreated control sites by laser-Doppler blood flowmetry (LDF). Whole body skin temperature (Tsk) was controlled by water-perfused suits, and esophageal temperature (Tes) was monitored as an index of internal temperature. Mean arterial pressure (MAP) was monitored and cutaneous vascular conductance was calculated as LDF/MAP. Sweat rate was also monitored by dew point hygrometry in 11 subjects. Tsk was raised to 38 degrees C, after which subjects began 20-30 min of exercise on a bicycle ergometer. The rate of the initial rapid increase in SkBF with increasing Tes was not altered by bretylium treatment (P > 0.05 between sites). The attenuation of the rate of rise during the latter phase of exercise was not abolished by bretylium treatment (P > 0.05 between sites); instead, there was a trend for the attenuation to be enhanced at those sites. We conclude that the attenuated rate of rise of SkBF is due to limitation of active vasodilator activity and not due to increased vasoconstrictor tone.(ABSTRACT TRUNCATED AT 250 WORDS)

Leg exercise conditioning increases peak forearm blood flow

1991 ◽  
Vol 71 (4) ◽  
pp. 1568-1573 ◽  
Author(s):  
D. Silber ◽  
D. McLaughlin ◽  
L. Sinoway
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Forearm Blood Flow ◽  
Circulatory Arrest ◽  
Bicycle Ergometer ◽  
O2 Consumption ◽  
Resting Heart Rate ◽  
Leg Exercise ◽  
Forearm Muscle ◽  
Bicycle Ergometer Training

To examine whether forearm vascular adaptations could occur after upright-leg exercise training, the reactive hyperemic blood flow after 10 min of forearm circulatory arrest (RHBF10) was studied. RHBF10 was examined in seven subjects before, at 2 wk, and after the completion of 4 wk of bicycle ergometer training. Maximal O2 consumption (VO2max) for leg ergometer work increased 13% (P less than 0.05) over 4 wk. Over that period of time RHBF10 in the forearm increased 50% (P less than 0.05), with a reciprocal drop in minimum vascular resistance. Resting heart rate decreased 15% (P less than 0.05) during the same period. Changes in RHBF10 and VO2max were noted after 2 wk of training. Mean arterial pressure did not change. We conclude that vascular adaptations can occur in the forearm muscle beds, even though the training regimen is designed to condition the lower extremities.

Nocturnal lowering of thresholds for sweating and vasodilation

1976 ◽  
Vol 41 (1) ◽  
pp. 15-19 ◽  
Author(s):  
C. B. Wenger ◽  
M. F. Roberts ◽  
J. A. Stolwijk ◽  
E. R. Nadel
Keyword(s):  
Blood Flow ◽  
Skin Temperature ◽  
Forearm Blood Flow ◽  
Aerobic Power ◽  
Weighted Average ◽  
Bicycle Ergometer ◽  
Maximal Aerobic Power ◽  
Esophageal Temperature ◽  
Mean Skin Temperature ◽  
Sweating Rate

Six subjects exercised on a bicycle ergometer at 60–70% of maximal aerobic power in a 25 degrees C ambient. Experiments on each subject wereconducted at night (4:00–5:30 A.M.) and in daytime (noon-4:30 P.M.).Chest sweating rate (msw) was measured with resistance hygrometry. Forearm blood flow (BF), with an arm skin temperature of 35.5 +/- 1.2 degrees C (SD), was measured with electrocapacitance plethysmography. Esophageal temperature (Tes) was measured with a thermocouple at the level of the left atriumand mean skin temperature (Tsk) was calculated from a weighted average of temperatures at three sites. Tes was corrected to a skin temperature of 33 degrees C as follows: T'es = Tes + (Tsk - 33 degrees C)/8. This correction reflects the relative contributions of Tes and Tsk to control of msw:T'es and BF:T'es relations were not consistently changed. In any given subject, thresholds for sweating and vasodilation were shifted about equally. These shifts averaged 0.57 degrees C (range: 0.23–0.93 degrees C)for msw and 0.63 degrees C (range: 0.17–0.98 degrees C)for BF.

Reflex control of active cutaneous vasodilation by skin temperature in humans

1994 ◽  
Vol 266 (5) ◽  
pp. H1979-H1984 ◽  
Author(s):  
P. E. Pergola ◽  
D. L. Kellogg ◽  
J. M. Johnson ◽  
W. A. Kosiba
Keyword(s):  
Blood Flow ◽  
Skin Temperature ◽  
Control Site ◽  
Whole Body ◽  
Entire Body ◽  
Internal Temperature ◽  
Doppler Flowmetry ◽  
Vasodilator Activity ◽  
Forearm Skin ◽  
Reflex Control

The purpose of this study was to examine whether reflex effects of changes in whole body skin temperature (Tsk) on cutaneous vasculature are mediated through the vasoconstrictor or the active vasodilator arm of the sympathetic nervous system. In six subjects, reflex responses in forearm skin blood flow (SkBF) to changes in Tsk were monitored by laser-Doppler flowmetry. SkBF was monitored at a control site and at a 0.6-cm2 site where bretylium (BT) had been iontophoretically applied to abolish sympathetic vasoconstrictor control. Reflex control of SkBF at BT-treated sites is solely through active vasodilator activity. An index of cutaneous vascular conductance (CVC) was calculated from the blood flow signal and mean arterial pressure, measured noninvasively. Data are expressed relative to maximum CVC (CVCmax) achieved by local warming of measurement sites to 42 degrees C at the end of each study. Tsk was controlled with a water-perfused suit covering the entire body except for the head and arms. Esophageal temperature (Tes) was measured as an index of internal temperature. In part A (rest), raising Tsk at rest from 31.9 +/- 0.3 to 36.7 +/- 0.2 degrees C increased CVC at control sites from 3 +/- 0.2 to 5 +/- 0.6% of CVCmax. CVC did not change at BT-treated sites, suggesting that at rest, with a normal internal temperature, reflex effects of raising Tsk on SkBF are mediated through vasoconstrictor withdrawal. In part B (exercise), exercise at a low Tsk increased Tes to 37.49 +/- 0.1 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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

1984 ◽  
Vol 56 (4) ◽  
pp. 930-935 ◽  
Author(s):  
W. L. Kenney ◽  
E. Kamon ◽  
E. R. Buskirk
Keyword(s):  
Blood Flow ◽  
Arterial Pressure ◽  
Core Temperature ◽  
Forearm Blood Flow ◽  
Impedance Plethysmography ◽  
Maximal Aerobic Capacity ◽  
Significant Linear Correlation ◽  
Actual Range ◽  
Leg Exercise ◽  
Cutaneous Blood

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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