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Dehydration affects cerebral blood flow but not its metabolic rate for oxygen during maximal exercise in trained humans.

Trangmar SJ, Chiesa ST, Stock CG, Kalsi KK, Secher NH, González-Alonso J - J. Physiol. (Lond.) (2014)

Bottom Line: In all conditions, reductions in ICA and MCA Vmean were associated with declining cerebral vascular conductance, increasing jugular venous noradrenaline, and falling arterial carbon dioxide tension (P aCO 2) (R(2) ≥ 0.41, P ≤ 0.01) whereas CCA flow and conductance were related to elevated blood temperature.In conclusion, dehydration accelerated the decline in CBF by decreasing P aCO 2 and enhancing vasoconstrictor activity.However, the circulatory strain on the human brain during maximal exercise does not compromise CMRO2 because of compensatory increases in O2 extraction.

View Article: PubMed Central - PubMed

Affiliation: Centre for Sports Medicine and Human Performance, Brunel University, London, UK.

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Cerebral haemodynamics and oxygen parameters during incremental exercise in different hydration statesLeft panel: internal carotid artery blood flow (A), ICA oxygen delivery (B), common carotid artery blood flow (C) and middle cerebral artery velocity (D). Right panel: jugular venous to arterial CO2 difference (v–a CO2; E), arterial to jugular venous oxygen difference (a–v O2; F), brain CO2 release (G), and brain oxygen uptake (CMRO2; H) for control (open circles), dehydration (filled circles) and rehydration (open squares) conditions. Values are mean ± SEM. P values represent ANOVA results. *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax).
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fig03: Cerebral haemodynamics and oxygen parameters during incremental exercise in different hydration statesLeft panel: internal carotid artery blood flow (A), ICA oxygen delivery (B), common carotid artery blood flow (C) and middle cerebral artery velocity (D). Right panel: jugular venous to arterial CO2 difference (v–a CO2; E), arterial to jugular venous oxygen difference (a–v O2; F), brain CO2 release (G), and brain oxygen uptake (CMRO2; H) for control (open circles), dehydration (filled circles) and rehydration (open squares) conditions. Values are mean ± SEM. P values represent ANOVA results. *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax).

Mentions: In control in the dehydration trial, ICA blood flow and MCA Vmean increased by ∼17 ± 2% from rest to submaximal exercise and thereafter declined to resting values (both P < 0.05; Fig. 3A and D). Conversely, during DEH, ICA blood flow did not increase from rest to moderate exercise, but declined to below resting values at WRmax (−11% vs. rest, P < 0.05). ICA blood flow responses to REH were similar to control. In all conditions, the decline in blood flow at high exercise intensities was associated with reductions in vessel diameter and blood velocity. In contrast to ICA blood flow, CCA blood flow did not change during low intensity exercise in control, but increased progressively with further increases in exercise intensity (rest = 0.47 ± 0.02 vs. 0.60 ± 0.02 l min−1, P < 0.01) (Fig. 3C). During DEH, CCA blood flow was elevated (P < 0.05) at the start of exercise and did not change throughout incremental exercise. CCA blood flow responses to REH incremental exercise were similar to control. The increases in CCA blood flow in control and REH were associated with increases in blood velocity (P < 0.05). In the euhydration trial, ICA and CCA blood flow, and MCA Vmean were similar at rest and during incremental exercise.


Dehydration affects cerebral blood flow but not its metabolic rate for oxygen during maximal exercise in trained humans.

Trangmar SJ, Chiesa ST, Stock CG, Kalsi KK, Secher NH, González-Alonso J - J. Physiol. (Lond.) (2014)

Cerebral haemodynamics and oxygen parameters during incremental exercise in different hydration statesLeft panel: internal carotid artery blood flow (A), ICA oxygen delivery (B), common carotid artery blood flow (C) and middle cerebral artery velocity (D). Right panel: jugular venous to arterial CO2 difference (v–a CO2; E), arterial to jugular venous oxygen difference (a–v O2; F), brain CO2 release (G), and brain oxygen uptake (CMRO2; H) for control (open circles), dehydration (filled circles) and rehydration (open squares) conditions. Values are mean ± SEM. P values represent ANOVA results. *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4214665&req=5

fig03: Cerebral haemodynamics and oxygen parameters during incremental exercise in different hydration statesLeft panel: internal carotid artery blood flow (A), ICA oxygen delivery (B), common carotid artery blood flow (C) and middle cerebral artery velocity (D). Right panel: jugular venous to arterial CO2 difference (v–a CO2; E), arterial to jugular venous oxygen difference (a–v O2; F), brain CO2 release (G), and brain oxygen uptake (CMRO2; H) for control (open circles), dehydration (filled circles) and rehydration (open squares) conditions. Values are mean ± SEM. P values represent ANOVA results. *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax).
Mentions: In control in the dehydration trial, ICA blood flow and MCA Vmean increased by ∼17 ± 2% from rest to submaximal exercise and thereafter declined to resting values (both P < 0.05; Fig. 3A and D). Conversely, during DEH, ICA blood flow did not increase from rest to moderate exercise, but declined to below resting values at WRmax (−11% vs. rest, P < 0.05). ICA blood flow responses to REH were similar to control. In all conditions, the decline in blood flow at high exercise intensities was associated with reductions in vessel diameter and blood velocity. In contrast to ICA blood flow, CCA blood flow did not change during low intensity exercise in control, but increased progressively with further increases in exercise intensity (rest = 0.47 ± 0.02 vs. 0.60 ± 0.02 l min−1, P < 0.01) (Fig. 3C). During DEH, CCA blood flow was elevated (P < 0.05) at the start of exercise and did not change throughout incremental exercise. CCA blood flow responses to REH incremental exercise were similar to control. The increases in CCA blood flow in control and REH were associated with increases in blood velocity (P < 0.05). In the euhydration trial, ICA and CCA blood flow, and MCA Vmean were similar at rest and during incremental exercise.

Bottom Line: In all conditions, reductions in ICA and MCA Vmean were associated with declining cerebral vascular conductance, increasing jugular venous noradrenaline, and falling arterial carbon dioxide tension (P aCO 2) (R(2) ≥ 0.41, P ≤ 0.01) whereas CCA flow and conductance were related to elevated blood temperature.In conclusion, dehydration accelerated the decline in CBF by decreasing P aCO 2 and enhancing vasoconstrictor activity.However, the circulatory strain on the human brain during maximal exercise does not compromise CMRO2 because of compensatory increases in O2 extraction.

View Article: PubMed Central - PubMed

Affiliation: Centre for Sports Medicine and Human Performance, Brunel University, London, UK.

Show MeSH
Related in: MedlinePlus