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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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Jugular venous [NA] during incremental exercise and relationship of ICA vascular conductance and jugular venous [NA]Jugular venous [NA] and the relationship between ICA vascular conductance and jugular venous [NA] in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar.
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fig08: Jugular venous [NA] during incremental exercise and relationship of ICA vascular conductance and jugular venous [NA]Jugular venous [NA] and the relationship between ICA vascular conductance and jugular venous [NA] in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar.

Mentions: At rest in DEH, arterial and jugular venous noradrenaline concentration ([NA]) was higher than control and rehydration (13 ± 4 vs. 3 ± 1 and 3 ± 1 nmol l−1 and 12 ± 4 vs. 2 ± 0.2 and 6 ± 2 nmol l−1, respectively; P < 0.05). From rest to WRmax, arterial and jugular venous [NA] increased exponentially in all conditions to a peak of 43 ± 10, 69 ± 19 and 82 ± 21 nmol l−1, and 36 ± 8, 39 ± 10 and 27 ± 5 nmol l−1 in dehydration, control and rehydration, respectively. The a–v [NA] differences and exchange across the brain remained stable in the three trials (Fig. 7). The reductions in ICA vascular conductance were correlated to an increased jugular venous [NA] (control R2 = −0.79, dehydration and rehydration R2 = −0.66; P < 0.05: Fig. 8B). On the other hand, arterial and jugular venous adrenaline concentration ([A]) was not different among conditions at rest (1.1 ± 0.3 vs. 0.8 ± 0.2 and 0.8 ± 0.2 nmol l−1 and 1.0 ± 0.3 vs. 0.7 ± 0.1 and 0.6 ± 0.1 nmol l−1, respectively). Yet, from rest to WRmax in dehydration, control and rehydration conditions, [A] increased to a peak of 5.5 ± 1.9, 9.1 ± 2.2 and 7.7 ± 2.8 nmol l−1 in arterial and 6.5 ± 2.4, 8.5 ± 3.6 and 3.3 ± 1.1 nmol l−1 in venous plasma, respectively (all P < 0.05). Lastly, arterial plasma [ATP] increased in a curvilinear manner from similar values at rest (1058 ± 177 vs. 938 ± 128 and 1027 ± 199 nmol l−1) to WRmax, and was higher in dehydration compared to control and rehydration at maximal intensities (1641 ± 189 vs. 1403 ± 221 and 1274 ± 188 nmol l−1; P < 0.05).


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)

Jugular venous [NA] during incremental exercise and relationship of ICA vascular conductance and jugular venous [NA]Jugular venous [NA] and the relationship between ICA vascular conductance and jugular venous [NA] in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig08: Jugular venous [NA] during incremental exercise and relationship of ICA vascular conductance and jugular venous [NA]Jugular venous [NA] and the relationship between ICA vascular conductance and jugular venous [NA] in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar.
Mentions: At rest in DEH, arterial and jugular venous noradrenaline concentration ([NA]) was higher than control and rehydration (13 ± 4 vs. 3 ± 1 and 3 ± 1 nmol l−1 and 12 ± 4 vs. 2 ± 0.2 and 6 ± 2 nmol l−1, respectively; P < 0.05). From rest to WRmax, arterial and jugular venous [NA] increased exponentially in all conditions to a peak of 43 ± 10, 69 ± 19 and 82 ± 21 nmol l−1, and 36 ± 8, 39 ± 10 and 27 ± 5 nmol l−1 in dehydration, control and rehydration, respectively. The a–v [NA] differences and exchange across the brain remained stable in the three trials (Fig. 7). The reductions in ICA vascular conductance were correlated to an increased jugular venous [NA] (control R2 = −0.79, dehydration and rehydration R2 = −0.66; P < 0.05: Fig. 8B). On the other hand, arterial and jugular venous adrenaline concentration ([A]) was not different among conditions at rest (1.1 ± 0.3 vs. 0.8 ± 0.2 and 0.8 ± 0.2 nmol l−1 and 1.0 ± 0.3 vs. 0.7 ± 0.1 and 0.6 ± 0.1 nmol l−1, respectively). Yet, from rest to WRmax in dehydration, control and rehydration conditions, [A] increased to a peak of 5.5 ± 1.9, 9.1 ± 2.2 and 7.7 ± 2.8 nmol l−1 in arterial and 6.5 ± 2.4, 8.5 ± 3.6 and 3.3 ± 1.1 nmol l−1 in venous plasma, respectively (all P < 0.05). Lastly, arterial plasma [ATP] increased in a curvilinear manner from similar values at rest (1058 ± 177 vs. 938 ± 128 and 1027 ± 199 nmol l−1) to WRmax, and was higher in dehydration compared to control and rehydration at maximal intensities (1641 ± 189 vs. 1403 ± 221 and 1274 ± 188 nmol l−1; P < 0.05).

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