Hydration and cardiovascular function! in exercise! José González-Alonso! Centre for Sports Medicine & Human Performance,! www.brunel.ac.uk/csmhp! ! Dehydration during exercise ! 4 L of sweat loss = ~ 0.4 L of plasma! (~ 6% BW) ! !~ 1.5 L interstitial! ! ! !~ 2 L intracellular! PLASMA INTERSTITIAL! INTRACELLULAR! Brain! Hydration and ! cardiovascular function! Heart! Systemic circulation! Skeletal muscle! ! Skin! Systemic circulation! Large fluid! Moderate fluid! Small fluid! No fluid! CO = HR x SV! Montain & Coyle J Appl Physiol 1992! Muscle and skin circulation! Dehydration Euhydration Trunk, head & arms 60% VO2max in 35ºC, 50% rh González-Alonso et al. J Physiol 1998! Cerebral Blood Flo (l.min-1) 0.40 Brain circulation0.35! 0.30 ** 0.25 0.20 ! Dehydration Middle Cerebral Artery Velocity (cm.s-1) Euhydration Steven Trangmar. ECSS presentation. ! Today 3:30PM Aula Magna 2! 80 70 60 ** 50 40 ! Dehydration Euhydration 0 20 40 60 80 100120 Time (min) Brain circulation! Middle cerebral artery blood velocity! * Garcia et al. Unpublished data! Why does cardiac output decline with dehydration?! 200 Stroke volume (ml) 160 120 Heart rate (beats/min) *† 40 ml! *† 80 *† *† 200 *† *† *† *† 160 120 0 20 40 60 80 100 120 140 Time (min) 28 beats/min! Mechanisms reducing stroke volume?! Cardiac output Heart rate Stroke volume! End-diastolic! End-systolic! volume! volume! Exercise in the cold! Supine exercise! Plasma volume restoration stroke volume (D), and systemic vascular con during the 20- to 30-min period of exercise in (35°C) when euhydrated and dehydrated by 1. weight. Values are means " SE for 8 subjects. * from euhydrated condition, P ! 0.05. † Signi exercise in cold, P ! 0.05. Euhydration Supine exercise and exercise in the cold attenuate the fall in SV! Stroke! volume! (ml)! Stroke! volume! (ml)! González-Alonso et al. Am J Physiol 1999, 2000! Dehydration was s systemic vascular conductance in the heat versus cold in Euh, Deh (Fig. 4E). During exercise in the hea lar conductance was significantly low and Deh-4.2 compared with Euh, bec values observed during exercise in t Fig. 4E). At all levels of hydration, forearm tance and cutaneous vascular conduc Cold Heat SV fall is associated with increased HR and reduced BV! ! Stroke Volume! (% change ! from control)! * * *† ! *† Heart Rate! (% change ! from control)! * * Hyperthermia Dehydration+ Dehydration Dehydration+ Hyperthermia BV Restoration González-Alonso et al. J Appl Physiol 1997 summarized in Table 2. Hemodynamics and global LV functio with dehydration and following rehydra cise, dehydration caused a reduction in E (all P ! 0.01). However, ESV was signifi at rest. Cardiac output and EF were main exercise conditions (both P " 0.05). Th blood volume during exercise was not s cant (P " 0.05). In contrast to resting exercise, MAP declined progressively w dehydration (P ! 0.01) and remained l exercise following rehydration (P ! 0.01 Unlike rest, dehydration during exercise tolic or diastolic LV twist indices (all P " LV untwisting velocity occurred prior to m at control rest (P " 0.01), with dehydrat rehydration at rest and during one-legged k cise, peak LV untwisting velocity tended to Dehydration during exercise reduced peak (P ! 0.01), whereas radial and circumf maintained (P " 0.05). Furthermore, dia strain rate decreased and remained lower fo (P ! 0.01). All other systolic and diastoli maintained (P " 0.05). Cardiac function at rest and during leg exercise! SV = EDV - ESV! DISCUSSION Fig. 2. Comparison of the effect of dehydration and rehydration on left ventricular volumes at rest (white bars) and during small muscle mass exercise (black bars) (n # 8). ESV: end-systolic volume; EDV: end-diastolic volume. Data represent mean $ SEM. *P ! 0.01 from control; †P ! 0.01 from 2% dehydration; ‡P ! 0.01 from 3.5% dehydration; #P ! 0.01 compared with the same condition at rest. J Appl Physiol • VOL The main aim of this study was to ex decline in SV, caused by dehydration and m temperatures at rest and during exercise, underpinned by impaired LV mechanics. T five novel findings: 1) dehydration signific at rest and during one-legged knee-extenso tolic twist mechanics are slightly enhanced rest and maintained during exercise; 3) dias ics are maintained with dehydration at rest a 4) systolic longitudinal strain and diastolic rates are slightly reduced with dehydration exercise; and 5) peak LV untwisting ve delayed with dehydration at rest and during the findings show that dehydration at res muscle mass exercise results in a large decli 111 • SEPTEMBER 2011 • www.jap.org Stöhr et al. J Appl Physiol 2011 Table 2). P= P= (r!2 = P= dratio chang P= Cardiovascular function at rest and during leg exercise Intravascular ATP and catecholamines with dehydration and rehydration Arterial and femoral venous plasma [ATP] were unchanged at rest but declined significantly with 2 and 3.5 % flow and leg vascular conductance increased while cardiac output did not change or increased, but both arterial and leg perfusion pressure declined with dehydrated and hyperthermia at rest and during one-legged knee-extensor exercise. The small increase in leg blood flow occurred despite significant increases in CaO2 and a reduction in plasma [ATP], and was accompanied by a parallel reduction in leg a–vO2 diff CaO2, plas active limb cannot be during sma haemoconc not reduce Pearson et al. Eur J Appl Physiol 2013 and 3.5 % dehydration and rema Table 2). At rest, Q_ (6.7 ± 0.2 L min ) and systemic rehydration (P \ 0.05). vascular conductance (68 ± 3 mL min-1 mmHg-1) Alterations in LBF with dehy remained elevated after rehydration (both P \ 0.05) while were unrelated to exercise changes(Pin\ C dehydration during 0 increased significantly from control with levels 2 % dehydration stroke volume was fully returned to control (P [ 0.05; -1 P = 0.48; rehydration, Fig. 4) and during following arterial plas (113 ± Table 2).3–126 ± 4 mL L , P \ 0.05) but was not different -1 P = 0.64), andcompared also arterial cantly reduced to contp with 3.5 % dehydration (117 ± 4 mL L ; P [ 0.05). 2 (r = 0.51, P =exercise 0.29) and whereas during both durin arter Following ATP rehydration, LBF and LVC remained elevated Intravascular and catecholamines Discontinuous single leg exercise! Continuous leg cycling! _ 2 P = 0.37). Increases andcompared decreas [ATP] remained reduced whereas leg a–vO2and difference remained reduced and leg VO with dehydration rehydration Pearson etwas al. Eur J Appl at Physiol González-Alonso et al.and J Physiol 1998 and dration rehydration, respectiv At rest, plasma arterial venou unchanged rest and2013 during exercise (Fig. 3). MAP was epinephrine unchanged 2 changes in were arterial plasmawith [AT not different to control at rest but [ATP] increased 3.5 % Arterial and femoral venous plasma werefrom unchanged 2 and rehydration (P [ P = following 0.92) and during exercise (r 0 exercise (106 ± 3 with vs. 111 3 mmHg; atdehydration rest but during declined significantly 2 ±and 3.5 % exercise, venous plasma norepinep P \ 0.05) yet remained lower than control (P 126! \ 0.05; 122! and 3.5 % dehydration and remai Euhydration! Table 2). At rest, Q_ (6.7 ± 0.2 L min-1) and systemic 118! -1 rehydration (P \ 0.05). vascular conductance (68 ± 3 mL min-1 mmHg 114! ) Alterations in LBF dehyd 4%with Dehydration! remained elevated after rehydration (both P \ 0.05) while 110! were unrelated to changes in Ca stroke volume was fully returned to control levels (P 106! [ 0.05; *† *† P = 0.48; Fig. 4) and during 102! Table 2). P = 0.64), and also arterial p 200! Downloaded from (r2 = 0.51, P = 0.29) and durin Intravascular ATP and catecholamines Euhydration! 190! P = 0.37). Increases and decrease with dehydration and rehydration 180! 4% Dehydration! dration and rehydration, respectiv 170! changes in arterial plasma [ATP Arterial and femoral venous plasma [ATP] were unchanged 160! * *† exercise (r2 P = 0.92) and during at rest but declined significantly with 2 and 3.5 % Differential vascular response to dehydration! Systemic vascular ! conductance! (mL/min/mmHg) ! ! Mean arterial ! pressure! (mmHg)! 150! 0 20 40 60 80 100 120 140! Time (min)! Differential catecholamine response to dehydration! Discontinuous single leg exercise! 4 González-Alonso et al. J Physiol 1998 24! Arterial noradrenaline! (nmol/L)! Rest Exercise 3 2 1 0 20! *† 16! *† 12! Euhydration! Downloaded fr 4% Dehydration! 8! 4! 0 20 40 60 80 100 120 140! ra R eh yd yd eh D 5% 3. tio tio ra ra yd eh D n n n tio ol tr on 2% *† *† 0! C Arterial noradrenaline (nmol/L) Pearson et al. Eur J Appl Physiol 2013 Continuous leg cycling! Time (min)! (P ! 0.01), whereas radial and circumferentia maintained (P " 0.05). Furthermore, diastolic strain rate decreased and remained lower followin (P ! 0.01). All other systolic and diastolic stra maintained (P " 0.05). Peripheral and cardiac function interactions! Fig. 2. Comparison of the effect of dehydration and rehydration on left ventricular volumes at rest (white bars) and during small muscle mass exercise (black bars) (n # 8). ESV: end-systolic volume; EDV: end-diastolic volume. Data represent mean $ SEM. *P ! 0.01 from control; †P ! 0.01 from 2% dehydration; ‡P ! 0.01 from 3.5% dehydration; #P ! 0.01 compared with the same condition at rest. * 0 www.jap.org 3. 5% D eh C yd ra on tro l 111 • SEPTEMBER 2011 • 2% J Appl Physiol • VOL The main aim of this study was to examine decline in SV, caused by dehydration and mildly e temperatures at rest and during exercise, woul underpinned by impaired LV mechanics. This st five novelRest findings: 1) dehydration significantly 25 Exercise at rest and during one-legged knee-extensor exe tolic twist mechanics are slightly enhanced with d 20 rest and maintained during exercise; 3) diastolic t ics are maintained with dehydration at rest and du 15 4) systolic longitudinal strain and diastolic longi rates are slightly reduced with dehydration at re 10 exercise; and 5) peak LV untwisting velocity delayed with dehydration at rest and during exerc 5 findings show that dehydration at rest and the muscle mass exercise results in a large decline in tio D n eh yd ra tio R n eh yd ra tio n Femoral beat volume (ml) DISCUSSION logy.org/ by guest on June 23, 2013 Peripheral and cardiac function interactions! Cardiac output! (l/min)! Q = SV * HR! Fig. 1. Stroke volume, blood volume, heart rate, esophageal temperature, forearm blood flow (FBF), and laser-Doppler cutaneous blood flow (CBF) responses during 60 min of exercise during "1-adrenoceptor-blockade (BB, p) and control (CON, k) treatments. Responses during 3- to 10- and 10- to 20-min periods (marked with brackets) were averaged to 5 and 15 min, respectively, for statistical analysis. Values are means # SE (n ! 7).* BB different from CON, P $ 0.05. † During CON, values at this time point are different from previous time point, P $ 0.05. ‡ During BB, values at this time point are different from previous time point, P $ 0.05. β-blockade Control Control (3rd step).] A legitimate criticism of this regres MAP sion analysis is that part of the association of HR and CO with SV occurs because HR, CO, and SV are not independently measured (i.e., SV is calculated from CO Rest! and HR). Therefore, a second regression analysis on SV 1. Cardiac was performed after HR and CO wereFigure excluded. When output (A), stroke volume conductance (D) as a function of heart rate HR and CO were excluded, esophageal temperature Data are means ± SEM. ∗ Significantly different fro was the only variable significantly associated with SV 2 resting conditions. different from exe (Rt ! 0.861). Esophageal temperature was not signifi- §Significantly Exercise! cantly associated with SV in the first regression analy- β-blockade ATP infusion! Downloaded from J Physiol Atrial pacing! Heart rate ! (beats/min)! Time (min) Fritzche et al. J Appl Physiol 1999 Stroke volume! (ml/beats)! sion analysis tested the strength of the association between SV as a dependent variable and HR, CO, CBF, FBF, forearm venous volume, MAP, esophageal temperature, mean skin temperature, and blood volume as independent variables. HR was entered in the first step [total R2 (Rt2) ! 0.908], CO in the second step (Rt2 ! 0.96), and MAP in the third step (Rt2 ! 0.976), with no further variables reaching statistical significance. [Rt2 illustrates the fraction of variance in SV explained by HR (1st step), HR and CO (2nd step), and HR, CO, and Bada et al. J Physiol 2012 Conclusions 1. Dehydration induces significant cardiovascular strain during intense whole body exercise in hot environments.! 2. This is characterised by reductions in cardiac output and blood flow to active muscles, skin and brain. ! 3. Reductions in SV are associated with tachycardia and reductions in blood volume.! 4. During low intensity exercise and resting conditions dehydration does still reduce SV due to reductions in left ventricular filling. ! 5. Locomotor blood flow and cardiac function are closely coupled.! 6. The effects of dehydration on cardiovascular function are dependent on amount of muscle mass recruited. ! 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