Effect of hyperosmolality on control of blood flow and sweating

1984 ◽  
Vol 57 (6) ◽  
pp. 1688-1695 ◽  
Author(s):  
S. M. Fortney ◽  
C. B. Wenger ◽  
J. R. Bove ◽  
E. R. Nadel
Keyword(s):  
Blood Flow ◽  
Maximal Exercise ◽  
Forearm Blood Flow ◽  
Fluid Restriction ◽  
O2 Consumption ◽  
Rest Interval ◽  
Ambient Conditions ◽  
Exercise Tests ◽  
Sweating Threshold ◽  
Humidity Environment

To study the effect of hyperosmolality on thermoregulatory responses, five men [average maximal O2 consumption (VO2 max) = 48 ml X kg-1 X min-1] cycled at 65-75% VO2max for up to 30 min in a 30 degrees C, 40% relative humidity environment under three conditions. First, control tests (C) were performed where preexercise plasma volume (PV) and osmolality (Osm) averaged 3,800 ml and 282 mosmol X kg-1, respectively. Second, exercise tests (D) were performed following dehydration induced by fluid restriction and mild exercise (30% VO2max) in hot (40 degrees C) ambient conditions. Each subject then rested in cool surroundings 1 h before performing the exercise test. Preexercise PV and Osm averaged 3,606 ml and 293 mosmol X kg-1, respectively. Third, exercise tests (I) were performed following dehydration, but during the 1-h rest interval, 3% saline was infused so that PV was restored to 3,826 ml and Osm averaged 294 mosmol X kg-1 prior to exercise. During D, esophageal temperatures (Tes) were significantly higher than C, an avg 0.56 degrees C after 20 min exercise due to a 0.22 degrees C increase in Tes threshold for vasodilation, a 39% reduction in slope of the forearm blood flow (BF)-Tes relationship, a 32% average reduction in maximal exercise BF, and a 0.22 degrees C increase in Tes sweating threshold. During I, responses were similar to D, except the BF-Tes slope and the maximum BF were not significantly different from C. Thus hyperosmolality modifies thermoregulation by elevating thresholds for both vasodilation and sweating even without decreases in PV.

Influence of graded dehydration on hyperthermia and cardiovascular drift during exercise

1992 ◽  
Vol 73 (4) ◽  
pp. 1340-1350 ◽  
Author(s):  
S. J. Montain ◽  
E. F. Coyle
Keyword(s):  
Blood Flow ◽  
Prolonged Exercise ◽  
Forearm Blood Flow ◽  
Sweat Rate ◽  
Sodium Concentration ◽  
O2 Consumption ◽  
Esophageal Temperature ◽  
Warm Environment ◽  
Cardiovascular Drift ◽  
Highly Correlated

This investigation determined the effect of different rates of dehydration, induced by ingesting different volumes of fluid during prolonged exercise, on hyperthermia, heart rate (HR), and stroke volume (SV). On four different occasions, eight endurance-trained cyclists [age 23 +/- 3 (SD) yr, body wt 71.9 +/- 11.6 kg, maximal O2 consumption 4.72 +/- 0.33 l/min] cycled at a power output equal to 62-67% maximal O2 consumption for 2 h in a warm environment (33 degrees C dry bulb, 50% relative humidity, wind speed 2.5 m/s). During exercise, they randomly received no fluid (NF) or ingested a small (SF), moderate (MF), or large (LF) volume of fluid that replaced 20 +/- 1, 48 +/- 1, and 81 +/- 2%, respectively, of the fluid lost in sweat during exercise. The protocol resulted in graded magnitudes of dehydration as body weight declined 4.2 +/- 0.1, 3.4 +/- 0.1, 2.3 +/- 0.1, and 1.1 +/- 0.1%, respectively, during NF, SF, MF, and LF. After 2 h of exercise, esophageal temperature (Tes), HR, and SV were significantly different among the four trials (P < 0.05), with the exception of NF and SF. The magnitude of dehydration accrued after 2 h of exercise in the four trials was linearly related with the increase in Tes (r = 0.98, P < 0.02), the increase in HR (r = 0.99, P < 0.01), and the decline in SV (r = 0.99, P < 0.01). LF attenuated hyperthermia, apparently because of higher skin blood flow, inasmuch as forearm blood flow was 20–22% higher than during SF and NF at 105 min (P < 0.05). There were no differences in sweat rate among the four trials. In each subject, the increase in Tes from 20 to 120 min of exercise was highly correlated to the increase in serum osmolality (r = 0.81-0.98, P < 0.02-0.19) and the increase in serum sodium concentration (r = 0.87-0.99, P < 0.01-0.13) from 5 to 120 min of exercise. In summary, the magnitude of increase in core temperature and HR and the decline in SV are graded in proportion to the amount of dehydration accrued during exercise.

Vasodilation contributes to the rapid hyperemia with rhythmic contractions in humans

1998 ◽  
Vol 76 (4) ◽  
pp. 418-427 ◽  
Author(s):  
J K Shoemaker ◽  
M E Tschakovsky ◽  
R L Hughson
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Perfusion Pressure ◽  
Blood Velocity ◽  
Pulsed Doppler ◽  
Contraction Rate ◽  
Handgrip Exercise ◽  
Arterial Diameter ◽  
Exercise Tests ◽  
Rhythmic Contractions

The hypothesis that the rapid increases in blood flow at the exercise onsetare exclusively due to the mechanical effects of the muscle pump was tested in six volunteersduring dynamic handgrip exercise. While supine, each subject completed a series of eightdifferent exercise tests in which brachial artery blood pressure (BP) was altered by25–30 mmHg (1 mmHg = 133.3 Pa) by positioning the arm above or below the heart.Two different weights, corresponding to 4.9 and 9.7% of maximal voluntary isometriccontraction, were raised and lowered at two different contraction rate schedules (1s:1s and 2s:2swork–rest) each with a 50% duty cycle. Beat-by-beat measures of mean blood velocity (MBV)(pulsed Doppler) were obtained at rest and for 5 min following step increases in work ratewith emphasis on the first 24 s. MBV was increased 50–100% above rest following the firstcontraction in both arm positions (p < 0.05). The increase in MBV from rest was greaterin the below position compared with above, and this effect was observed following the first andsubsequent contractions (p < 0.05). However, the positional effect on the increase inMBV could not be explained entirely by the ~40% greater BP in this position. Also, the greaterworkload resulted in greater increases in MBV as early as the first contraction, compared withthe light workload (p < 0.05) despite similar reductions in forearm volume followingsingle contractions. MBV was greater with faster contraction rate tests by 8 s of exercise. Itwas concluded that microvascular vasodilation must act in concert with a reduction in venouspressure to increase forearm blood flow within the initial 2–4 s of exercise.Key words: Doppler, mean blood velocity, arterial diameter,handgrip exercise, perfusion pressure.

Forearm Blood Flow Response to an Acute Maximal Exercise Bout in Obese and Normal Weight Males

2011 ◽  
Vol 43 (Suppl 1) ◽  
pp. 740-741
Author(s):  
R. Lee Franco ◽  
Bennett A. Fallow ◽  
Chun-Jung Huang ◽  
Edmund Acevedo ◽  
James Arrowood ◽  
...  
Keyword(s):  
Blood Flow ◽  
Maximal Exercise ◽  
Forearm Blood Flow ◽  
Exercise Bout ◽  
Normal Weight ◽  
Blood Flow Response ◽  
Flow Response

O2 consumption during exercise in dogs--roles of splenic contraction and alpha-adrenergic vasoconstriction

1986 ◽  
Vol 251 (3) ◽  
pp. H502-H509 ◽  
Author(s):  
J. C. Longhurst ◽  
T. I. Musch ◽  
G. A. Ordway
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Adrenergic Receptor ◽  
Maximal Exercise ◽  
Adrenergic Blockade ◽  
Receptor Blockade ◽  
O2 Consumption ◽  
Alpha Adrenergic Receptor ◽  
O2 Extraction ◽  
Adrenergic Receptor Blockade

To examine the influence of alpha-adrenergic vasoconstriction on the aerobic capacity of dogs, we calculated O2 consumption (VO2) by the Fick method during submaximal and maximal exertion before and during alpha-adrenergic blockade with phentolamine. Regional blood flow was measured with radioactive microspheres. alpha-Adrenergic receptor blockade reduced VO2 by 12.9% during submaximal and 17.9% during maximal exercise. Arterial and venous lactic acid approximately doubled during both levels of stress in the presence of alpha-adrenergic receptor blockade. Calculated VO2 decreased because arteriovenous O2 (A-V)O2 extraction was reduced by 11.6% during submaximal exercise. During maximal exercise a 16.7% decrease in (A-V)O2 extraction and a 5.7% decrease in cardiac output contributed to the decrease in maximal VO2. During both levels of stress, (A-V)O2 extraction was reduced because arterial O2 content was decreased. Since circulating hematocrits during exercise were reduced by alpha-adrenergic receptor blockade (43-38%), we postulate that splenic contraction likely was inhibited. Additionally, distribution of blood flow to skeletal muscle and visceral organs was unaltered by alpha-blockade. To examine the importance of splenic contraction during maximal exercise, we examined hemodynamic and metabolic responses before and after splenectomy. Compared with the spleen-intact condition, splenectomized dogs demonstrated a 12.6% reduction in VO2 as a result of 7.7 and 5.5% reductions in (A-V)O2 extraction and cardiac output, respectively. (A-V)O2 extraction was reduced because arterial O2 content and circulating hematocrit during exercise were decreased. Therefore, in the exercising dog, alpha-adrenergic receptor blockade reduces O2 consumption and causes a shift to anaerobic metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Racial Differences In Forearm Blood Flow With Maximal Exercise Before And After Aerobic Training

2014 ◽  
Vol 46 ◽  
pp. 11
Author(s):  
Rebecca M. Kappus ◽  
Sushant M. Ranadive ◽  
Huimin Yan ◽  
Abbi D. Lane ◽  
Marc D. Cook ◽  
...  
Keyword(s):  
Blood Flow ◽  
Racial Differences ◽  
Aerobic Training ◽  
Maximal Exercise ◽  
Forearm Blood Flow ◽  
Before And After

scholarly journals Effects of ATP-induced leg vasodilation on V̇o2 peak and leg O2 extraction during maximal exercise in humans

2006 ◽  
Vol 291 (2) ◽  
pp. R447-R453 ◽  
Author(s):  
J. A. L. Calbet ◽  
C. Lundby ◽  
M. Sander ◽  
P. Robach ◽  
B. Saltin ◽  
...  
Keyword(s):  
Blood Flow ◽  
Maximal Exercise ◽  
Muscle Fibers ◽  
Isotonic Saline ◽  
Whole Body ◽  
Active Muscle ◽  
Vascular Conductance ◽  
Exercise Tests ◽  
Leg Blood Flow ◽  
Exercise In Humans

During maximal whole body exercise V̇o2 peak is limited by O2 delivery. In turn, it is though that blood flow at near-maximal exercise must be restrained by the sympathetic nervous system to maintain mean arterial pressure. To determine whether enhancing vasodilation across the leg results in higher O2 delivery and leg V̇o2 during near-maximal and maximal exercise in humans, seven men performed two maximal incremental exercise tests on the cycle ergometer. In random order, one test was performed with and one without (control exercise) infusion of ATP (8 mg in 1 ml of isotonic saline solution) into the right femoral artery at a rate of 80 μg·kg body mass−1·min−1. During near-maximal exercise (92% of V̇o2 peak), the infusion of ATP increased leg vascular conductance (+43%, P < 0.05), leg blood flow (+20%, 1.7 l/min, P < 0.05), and leg O2 delivery (+20%, 0.3 l/min, P < 0.05). No effects were observed on leg or systemic V̇o2. Leg O2 fractional extraction was decreased from 85 ± 3 (control) to 78 ± 4% (ATP) in the infused leg ( P < 0.05), while it remained unchanged in the left leg (84 ± 2 and 83 ± 2%; control and ATP; n = 3). ATP infusion at maximal exercise increased leg vascular conductance by 17% ( P < 0.05), while leg blood flow tended to be elevated by 0.8 l/min ( P = 0.08). However, neither systemic nor leg peak V̇o2 values where enhanced due to a reduction of O2 extraction from 84 ± 4 to 76 ± 4%, in the control and ATP conditions, respectively ( P < 0.05). In summary, the V̇o2 of the skeletal muscles of the lower extremities is not enhanced by limb vasodilation at near-maximal or maximal exercise in humans. The fact that ATP infusion resulted in a reduction of O2 extraction across the exercising leg suggests a vasodilating effect of ATP on less-active muscle fibers and other noncontracting tissues and that under normal conditions these regions are under high vasoconstrictor influence to ensure the most efficient flow distribution of the available cardiac output to the most active muscle fibers of the exercising limb.

Noninvasive diffusing capacity and cardiac output in exercising dogs

1988 ◽  
Vol 65 (2) ◽  
pp. 669-674 ◽  
Author(s):  
J. I. Carlin ◽  
S. S. Cassidy ◽  
U. Rajagopal ◽  
P. S. Clifford ◽  
R. L. Johnson
Keyword(s):  
Blood Flow ◽  
Body Weight ◽  
Cardiac Output ◽  
Steady State ◽  
Pulmonary Blood Flow ◽  
Maximal Exercise ◽  
O2 Consumption ◽  
Diffusing Capacity ◽  
Metabolic Capacity ◽  
End Tidal

We have developed a rebreathing procedure to determine diffusing capacity (DLCO) and pulmonary blood flow (Qc) in the awake, exercising dog. A low dead space, leak-free respiratory mask with an incorporated mouthpiece was utilized to achieve mixing between the rebreathing bag and the dog's lung. The rebreathing bag was initially filled with approximately 1.0 liter of gas containing 0.6% C2H2, 0.3% C18O, 9% He, and 35-40% O2. End-tidal gas concentrations were measured with a respiratory mass spectrometer. The disappearance of C2H2 and C18O was measured with respect to He to calculate Qc and DLCO. Values for DLCO in dogs, expressed per kilogram of body weight, were much larger than those reported in humans. However, at a given level of absolute O2 consumption, measurements of absolute DLCO in dogs were comparable to those reported in humans by both rebreathing and steady-state methods at rest and near-maximal exercise. These results suggest that DLCO is more closely matched to the metabolic capacity (i.e., maximal O2 consumption) than to body size between these two species.

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.

Association between post-ischemic forearm blood flow and blood pressure response to maximal exercise in well trained healthy young men

2006 ◽  
Vol 111 (3) ◽  
pp. 394-398 ◽  
Author(s):  
L. Aldo Ferrara ◽  
Vittorio Palmieri ◽  
Stefania Limauro ◽  
Stefania Viola ◽  
Emiliano Antonio Palmieri ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Maximal Exercise ◽  
Forearm Blood Flow ◽  
Blood Pressure Response ◽  
Young Men ◽  
Pressure Response
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