scholarly journals Exercise Heat Acclimation With Dehydration Does Not Affect Vascular and Cardiac Volumes or Systemic Hemodynamics During Endurance Exercise

2021 ◽  
Vol 12 ◽  
Author(s):  
Gavin Travers ◽  
José González-Alonso ◽  
Nathan Riding ◽  
David Nichols ◽  
Anthony Shaw ◽  
...  
Keyword(s):  
Endurance Exercise ◽  
Sweat Rate ◽  
Cardiovascular Responses ◽  
Heat Acclimation ◽  
Left Ventricular ◽  
Systemic Hemodynamics ◽  
Thermal Stimulus ◽  
Before And After ◽  
Cardiac Volumes ◽  
Experimental Trials

Permissive dehydration during exercise heat acclimation (HA) may enhance hematological and cardiovascular adaptations and thus acute responses to prolonged exercise. However, the independent role of permissive dehydration on vascular and cardiac volumes, ventricular-arterial (VA) coupling and systemic hemodynamics has not been systematically investigated. Seven males completed two 10-day exercise HA interventions with controlled heart rate (HR) where euhydration was maintained or permissive dehydration (-2.9 ± 0.5% body mass) occurred. Two experimental trials were conducted before and after each HA intervention where euhydration was maintained (-0.5 ± 0.4%) or dehydration was induced (-3.6 ± 0.6%) via prescribed fluid intakes. Rectal (Tre) and skin temperatures, HR, blood (BV) and left ventricular (LV) volumes, and systemic hemodynamics were measured at rest and during bouts of semi-recumbent cycling (55% V̇O2peak) in 33°C at 20, 100, and 180 min. Throughout HA sweat rate (12 ± 9%) and power output (18 ± 7 W) increased (P < 0.05), whereas Tre was 38.4 ± 0.2°C during the 75 min of HR controlled exercise (P = 1.00). Neither HA intervention altered resting and euhydrated exercising Tre, BV, LV diastolic and systolic volumes, systemic hemodynamics, and VA coupling (P > 0.05). Furthermore, the thermal and cardiovascular strain during exercise with acute dehydration post-HA was not influenced by HA hydration strategy. Instead, elevations in Tre and HR and reductions in BV and cardiac output matched pre-HA levels (P > 0.05). These findings indicate that permissive dehydration during exercise HA with controlled HR and maintained thermal stimulus does not affect hematological or cardiovascular responses during acute endurance exercise under moderate heat stress with maintained euhydration or moderate dehydration.

The Effects of Creatine Supplementation on Cardiovascular, Metabolic, and Thermoregulatory Responses during Exercise in the Heat in Endurance-Trained Humans

2004 ◽  
Vol 14 (4) ◽  
pp. 443-460 ◽  
Author(s):  
L.P. Kilduff ◽  
E. Georgiades ◽  
N. James ◽  
R.H. Minnion ◽  
M. Mitchell ◽  
...  
Keyword(s):  
Prolonged Exercise ◽  
Sweat Rate ◽  
Creatine Supplementation ◽  
Cardiovascular Responses ◽  
Constant Load ◽  
Time To Exhaustion ◽  
Exercise Tests ◽  
Thermoregulatory Responses ◽  
Before And After ◽  
Constant Load Exercise

The effects of creatine (Cr) supplementation on cardiovascular, metabolic, and thermoregulatory responses, and on the capacity of trained humans to perform prolonged exercise in the heat was examined. Endurance-trained males (n = 21) performed 2 constant-load exercise tests to exhaustion at 63 ± 5 % VO2max in the heat (ambient temperature: 30.3 ± 0.5 °C) before and after 7 d of Cr (20 g · d–1 ’ Cr + 140 g • d–1 glucose polymer) or placebo. Cr increased intraccl-lular water and reduced thermoregulatory and cardiovascular responses (e.g., heart rate, rectal temperature, sweat rate) but did not significantly increase time to exhaustion (47.0 ± 4.7 min vs. 49.7 ± 7.5 min, P = 0.095). Time to exhaustion was increased significantly in subjects whose estimated intramuscular Cr levels were substantially increased (“responders”: 47.3 ± 4.9 min vs. 51.7 ± 7.4 min, P = 0.031). Cr-induced hyperhydration can result in a more efficient thermoregulatory response during prolonged exercise in the heat.

Assessment of cardiac volumes and left ventricular mass by cine computed tomography before and after mitral balloon commissurotomy

1994 ◽  
Vol 128 (3) ◽  
pp. 533-539 ◽  
Author(s):  
Maleah Grover-McKay ◽  
Robert M. Weiss ◽  
Byron F. Vandenberg ◽  
Trudy L. Burns ◽  
Geoffrey J. Weidner ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Left Ventricular Mass ◽  
Left Ventricular ◽  
Ventricular Mass ◽  
Before And After ◽  
Cardiac Volumes

Influence of air velocity and heat acclimation on human skin wettedness and sweating efficiency

1979 ◽  
Vol 47 (6) ◽  
pp. 1194-1200 ◽  
Author(s):  
V. Candas ◽  
J. P. Libert ◽  
J. J. Vogt
Keyword(s):  
Sweat Rate ◽  
Water Vapor Pressure ◽  
Thermal Conditions ◽  
Heat Acclimation ◽  
Air Velocity ◽  
Experimental Conditions ◽  
Wind Speeds ◽  
Skin Wettedness ◽  
Before And After ◽  
Sweating Efficiency

Before and after heat acclimation, four male resting subjects were exposed to humid heat that caused levels of skin wettedness ranging from 50 to 100%. The physical experimental conditions were chosen so that the same skin wettedness was attained with modification of only the ambient water vapor pressure, at two wind speeds (0.6 and 0.9 m . s-1). The esophageal temperature (Tes), mean skin temperature (Tsk), sweating rate (msw), and dripping sweat rate (mdr) were recorded; the amounts of local drippage in the same thermal conditions before and after acclimation were also determined. The relationship between the evaporative efficiency of sweating (eta sw) and the skin wettedness (w) is reported, as is the influence of the subject's acclimation to humid heat on adjustments of skin wettedness. The effects of the air velocity on the coefficient of evaporation and on sweating efficiency are discussed. Beneficial increases in evaporation were achievable by increasing skin wettedness only when there was a consistent drippage, which differed from one body area to another and from one subject to another. The relation of drift in body temperature to skin wettedness changed with the acclimation of the subjects.

Cardiac responses to stimulation of thoracic afferents in the primate and canine

1976 ◽  
Vol 231 (4) ◽  
pp. 1279-1284 ◽  
Author(s):  
DR Kostreva ◽  
GL Hess ◽  
EJ Zuperku ◽  
J Neumark ◽  
RL Coon ◽  
...  
Keyword(s):  
Carotid Sinus ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Cardiac Responses ◽  
Afferent Nerves ◽  
Before And After ◽  
Blood Pressures ◽  
Bilateral Vagotomy ◽  
Upper Thoracic ◽  
Stimulation Of

Excitatory cardiovascular responses to electrically stimulated upper thoracic sympathetic afferent nerves were observed in halothane-anesthetized mongrel dogs and monkeys. The central end of the transected ventral limb of the left ansa subclavia was stimulated before and after several types of denervation. Significant increases in right and left ventricular maximum systolic pressures, systolic and diastolic systemic blood pressures, and aortic flow were observed. The carotid sinuses were denervated bilaterally and stimulation of the ansa was repeated. The cardiovascular responses to stimulation of the ventral ansa after carotid sinus denervation were greater in magnitude than those observed prior to denervation. This carotid sinus modulation of cardiovascular responses was observed in dogs and monkeys. Cardiovascular responses to stimulation of the ventral ansa after bilateral vagotomy were significantly less than the responses observed after carotid sinus denervation prior to vagotomy. However, the responses after vagotomy were statistically identical to responses obtained while stimulating the ventral ansa when the carotid sinuses and vagi remained intact.

Cardiovascular reflexes elicited by passive gastric distension in anesthetized cats

1981 ◽  
Vol 240 (4) ◽  
pp. H539-H545 ◽  
Author(s):  
J. C. Longhurst ◽  
H. L. Spilker ◽  
G. A. Ordway
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Diastolic Pressure ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Reflex Response ◽  
Gastric Distension ◽  
Cardiovascular Reflexes ◽  
Myocardial Oxygen Demand ◽  
Before And After

Hemodynamic responses to passive gastric distension were examined in alpha-chloralose anesthetized cats. Gastric balloons were distended with 37 degrees C fluid at slow (50 ml/min) and rapid (250 ml/min) infusion rates before and after laparotomy. Passive gastric distension at the slow infusion rate significantly (P less than 0.05) increased mean arterial pressure (MAP) by 28%, dP/dt at 40 mmHg developed pressure by 29%, and systemic vascular resistance (SVR) by 35%. Likewise, the rapid distension rate significantly (P less than 0.05) increased MAP (20%), dP/dt (16%), and SVR (23%). Heart rate, aortic flow, and left ventricular end-diastolic pressure remained unchanged at both distension rates. Cardiovascular responses to passive gastric distension were similar before and after laparotomy. Section of the vagus nerve at the diaphragm did not alter the responses, whereas abdominal splanchnic nerve section significantly (P less than 0.05) reduced the changes in mean arterial pressure and dP/dt. These results indicate that passive gastric distension in the cat elicits cardiovascular reflexes sufficient to increase myocardial oxygen demand. Such a reflex response could potentially contribute to postprandial angina in humans.

Exercise training enhances cardiac function in response to an afterload stress in older men

1997 ◽  
Vol 272 (2) ◽  
pp. H995-H1000 ◽  
Author(s):  
R. J. Spina ◽  
M. J. Turner ◽  
A. A. Ehsani
Keyword(s):  
Exercise Training ◽  
Left Ventricular Function ◽  
Flow Velocity ◽  
Ventricular Function ◽  
Endurance Exercise ◽  
Left Ventricular ◽  
Healthy Men ◽  
Endurance Exercise Training ◽  
Before And After ◽  
Phenylephrine Infusion

This study was designed to characterize cardiac adaptations to endurance exercise training in older healthy men by evaluation of changes in left ventricular function in response to an afterload stress in the presence of cardiac muscarinic receptor blockade. Eight men 65 +/- 2 (SE) yr old underwent 9 mo of endurance exercise training. Maximal O2 uptake (V(O2 max)) was determined during treadmill exercise. Left ventricular function was assessed with two-dimensional echocardiography and pulsed Doppler transmitral flow velocity profile at baseline, after an intravenous bolus of atropine and during infusion of graded doses of phenylephrine. V(O2 max) was increased by 29% in response to training (28.9 +/- 1 to 37.3 +/- 1 ml x kg(-1) x min(-1)). Baseline end-diastolic diameter (EDD) was increased, with no change in left ventricular wall thickness-to-radius ratio, after training, suggestive of eccentric left ventricular hypertrophy. EDD, end-systolic dimension, and end-systolic wall stress (sigma(es)) increased similarly in response to phenylephrine before and after training. Fractional shortening (FS) decreased in response to phenylephrine before but not after training. When the changes in FS (delta FS) during phenylephrine infusion were plotted as a function of changes in sigma(es), delta FS were significantly higher after than before training (P = 0.003) at comparable increases in sigma(es), indicative of improved contractile function. This adaptive response was preload independent, because EDD did not differ between the trained and untrained states during phenylephrine infusion. Heart rate responses to phenylephrine were similar before and after training. Exercise training resulted in a higher (P = 0.028) early-to-late transmitral diastolic flow velocity ratio at virtually identical heart rates, suggestive of improved diastolic filling. The results suggest that endurance exercise training induces an enhancement of left ventricular systolic function in response to an afterload stress in older healthy men.

scholarly journals Exercise heat acclimation has minimal effects on left ventricular volumes, function and systemic hemodynamics in euhydrated and dehydrated trained humans

2020 ◽  
Vol 319 (5) ◽  
pp. H965-H979
Author(s):  
Gavin Travers ◽  
José González-Alonso ◽  
Nathan Riding ◽  
David Nichols ◽  
Anthony Shaw ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Left Ventricle ◽  
Blood Volume ◽  
Heat Acclimation ◽  
Left Ventricular ◽  
Systemic Hemodynamics ◽  
Diastolic Filling ◽  
Left Ventricular Volumes ◽  
Ventricular Volumes

This study demonstrates that 10 days of exercise heat acclimation has minimal effects on left ventricular volumes, intrinsic cardiac function, and systemic hemodynamics during prolonged, repeated semirecumbent exercise in moderate heat, where heart rate and blood volume are similar to preacclimation levels. However, progressive dehydration is consistently associated with similar degrees of hyperthermia and tachycardia and reductions in blood volume, diastolic filling of the left ventricle, stroke volume, and cardiac output, regardless of acclimation state.

Hypohydration and exercise: effects of heat acclimation, gender, and environment

1983 ◽  
Vol 55 (4) ◽  
pp. 1147-1153 ◽  
Author(s):  
M. N. Sawka ◽  
M. M. Toner ◽  
R. P. Francesconi ◽  
K. B. Pandolf
Keyword(s):  
Aerobic Power ◽  
Sweat Rate ◽  
Heat Rate ◽  
Heat Acclimation ◽  
Experimental Conditions ◽  
Exercise Tests ◽  
Men And Women ◽  
Before And After ◽  
Hot Environments ◽  
Cardiovascular Strain

This study examined the effects of heat acclimation and subject gender on treadmill exercise in comfortable (20 degrees C, 40% rh), hot-dry (49 degrees C, 20% rh), and hot-wet (35 degrees C, 79% rh) environments while subjects were hypo- or euhydrated. Six male and six female subjects, matched for maximal aerobic power and percent body fat, completed two exercise tests in each environment both before and after a 10-day heat acclimation program. One exercise test was completed during euhydration and one during hypohydration (-5.0% from baseline body weight). In general, no significant (P greater than 0.05) differences were noted between men and women at the completion of exercise for rectal temperature (Tre), mean skin temperature (Tsk), or heat rate (HR) during any of the experimental conditions. Hypohydration generally increased Tre and HR values and decreased sweat rate values while not altering Tsk values. In the hypohydration experiments, heat acclimation significantly reduced Tre (0.19 degrees C) and HR (13 beats X min-1) values in the comfortable environment, but only HR values were reduced in hot-dry (21 beats X min-1) and hot-wet (21 beats X min-1) environments. The present findings indicated that men and women respond in a physiologically similar manner to hypohydration during exercise. They also indicated that for hypohydrated subjects heat acclimation decreased thermoregulatory and cardiovascular strain in a comfortable environment, but only cardiovascular strain decreased in hot environments.

Management of Ventricular Fibrillation during Acute Myocardial Infarction

1984 ◽  
Vol 23 (04) ◽  
pp. 209-213
Author(s):  
B. J. Northover
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Ventricular Fibrillation ◽  
Coronary Care Unit ◽  
Patient Survival ◽  
Left Ventricular ◽  
Ventricular Failure ◽  
Before And After ◽  
Coronary Care ◽  
The Creation

SummaryAnalysis of electrocardiograms tape-recorded from patients admitted to hospital with acute myocardial infarction revealed that the pattern of ventricular extrasystolic activity was not significantly different among those who subsequently developed ventricular fibrillation and those who did not. Episodes of ventricular fibrillation occurred predominantly within 4 hours from the start of infarction. Patients were 3 times less likely to survive an episode of ventricular fibrillation if they also had left ventricular failure than if this feature was absent. Management of episodes of ventricular fibrillation was compared in patients before and after the creation of a specially staffed and equipped coronary care unit. The success of electric shock as a treatment for ventricular fibrillation was similar before and after the creation of the coronary care unit. An attempt was made to determine which features in the management of ventricular fibrillation in this and in previously published series were associated with patient survival.

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