TY - JOUR

T1 - Cerebral oxygenation is reduced during hyperthermic exercise in humans

AU - Rasmussen, Peter

AU - Nybo, Lars

AU - Volianitis, S.

AU - Møller, K.

AU - Secher, Niels H.

AU - Gjedde, Albert

AU - Rasmussen, Peter

AU - Nybo, L

AU - Volianitis, Stefanos

AU - Møller, Kirsten

AU - Secher, N H

AU - Gjedde, Albert

N1 - CURIS 2010 5200 055

PY - 2010/5/1

Y1 - 2010/5/1

N2 - Abstract Aim: Cerebral mitochondrial oxygen tension (P(mito)O(2)) is elevated during moderate exercise, while it is reduced when exercise becomes strenuous, reflecting an elevated cerebral metabolic rate for oxygen (CMRO(2)) combined with hyperventilation-induced attenuation of cerebral blood flow (CBF). Heat stress challenges exercise capacity as expressed by increased rating of perceived exertion (RPE). Methods: This study evaluated the effect of heat stress during exercise on P(mito)O(2) calculated based on a Kety-Schmidt-determined CBF and the arterial-to-jugular venous oxygen differences in eight males [27 +/- 6 years (mean +/- SD) and maximal oxygen uptake (VO(2max)) 63 +/- 6 mL kg(-1) min(-1)]. Results: The CBF, CMRO(2) and P(mito)O(2) remained stable during 1 h of moderate cycling (170 +/- 11 W, approximately 50% of VO(2max), RPE 9-12) in normothermia (core temperature of 37.8 +/- 0.4 degrees C). In contrast, when hyperthermia was provoked by dressing the subjects in watertight clothing during exercise (core temperature 39.5 +/- 0.2 degrees C), P(mito)O(2) declined by 4.8 +/- 3.8 mmHg (P < 0.05 compared to normothermia) because CMRO(2) increased by 8 +/- 7% at the same time as CBF was reduced by 15 +/- 13% (P < 0.05). During exercise with heat stress, RPE increased to 19 (19-20; P < 0.05); the RPE correlated inversely with P(mito)O(2) (r(2) = 0.42, P < 0.05). Conclusion: These data indicate that strenuous exercise in the heat lowers cerebral P(mito)O(2), and that exercise capacity in this condition may be dependent on maintained cerebral oxygenation.

AB - Abstract Aim: Cerebral mitochondrial oxygen tension (P(mito)O(2)) is elevated during moderate exercise, while it is reduced when exercise becomes strenuous, reflecting an elevated cerebral metabolic rate for oxygen (CMRO(2)) combined with hyperventilation-induced attenuation of cerebral blood flow (CBF). Heat stress challenges exercise capacity as expressed by increased rating of perceived exertion (RPE). Methods: This study evaluated the effect of heat stress during exercise on P(mito)O(2) calculated based on a Kety-Schmidt-determined CBF and the arterial-to-jugular venous oxygen differences in eight males [27 +/- 6 years (mean +/- SD) and maximal oxygen uptake (VO(2max)) 63 +/- 6 mL kg(-1) min(-1)]. Results: The CBF, CMRO(2) and P(mito)O(2) remained stable during 1 h of moderate cycling (170 +/- 11 W, approximately 50% of VO(2max), RPE 9-12) in normothermia (core temperature of 37.8 +/- 0.4 degrees C). In contrast, when hyperthermia was provoked by dressing the subjects in watertight clothing during exercise (core temperature 39.5 +/- 0.2 degrees C), P(mito)O(2) declined by 4.8 +/- 3.8 mmHg (P < 0.05 compared to normothermia) because CMRO(2) increased by 8 +/- 7% at the same time as CBF was reduced by 15 +/- 13% (P < 0.05). During exercise with heat stress, RPE increased to 19 (19-20; P < 0.05); the RPE correlated inversely with P(mito)O(2) (r(2) = 0.42, P < 0.05). Conclusion: These data indicate that strenuous exercise in the heat lowers cerebral P(mito)O(2), and that exercise capacity in this condition may be dependent on maintained cerebral oxygenation.

U2 - 10.1111/j.1748-1716.2010.02084.x

DO - 10.1111/j.1748-1716.2010.02084.x

M3 - Journal article

C2 - 20102344

VL - 199

SP - 63

EP - 70

JO - Acta Physiologica

JF - Acta Physiologica

SN - 1748-1708

IS - 1

ER -