Heat stress exacerbates the reduction in middle cerebral artery blood velocity during prolonged self-paced exercise

J. D. Périard, Sebastien Racinais

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

This study examined the influence of hyperthermia on middle cerebral artery mean blood velocity (MCA Vmean). Eleven cyclists undertook a 750kJ self-paced time trial in HOT (35°C) and COOL (20°C) conditions. Exercise time was longer in HOT (56min) compared with COOL (49min; P<0.001). Power output in HOT was significantly lower from 40% of work completed onward (P<0.01). Rectal temperature increased to 39.6±0.6°C (HOT) and 38.8±0.5°C (COOL; P<0.01). Skin temperature, skin blood flow, and heart rate were higher throughout HOT compared with COOL (P<0.05). A similar increase in ventilation (P<0.05) and decrease in end-tidal partial pressure of CO2 (PETCO2; P<0.05) occurred in both conditions. Arterial blood pressure and oxygen uptake were lower from 50% of work completed onward in HOT compared with COOL (P<0.01). MCA Vmean increased at 10% in both conditions (P<0.01), decreasing thereafter (P<0.01) and to a greater extent in HOT from 40% of work completed onward (P<0.05). Therefore, despite a comparable ventilatory response and PETCO2 in the HOT and COOL conditions, the greater level of thermal strain developing in the heat appears to have exacerbated the reduction in MCA Vmean, in part via increases in peripheral blood flow and a decrease in arterial blood pressure.

Original languageEnglish
Pages (from-to)135-144
Number of pages10
JournalScandinavian Journal of Medicine and Science in Sports
Volume25
Issue numberS1
DOIs
Publication statusPublished - 1 Jun 2015
Externally publishedYes

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Middle Cerebral Artery
Hot Temperature
Arterial Pressure
Skin Temperature
Partial Pressure
Ventilation
Fever
Heart Rate
Oxygen
Skin
Temperature

Cite this

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title = "Heat stress exacerbates the reduction in middle cerebral artery blood velocity during prolonged self-paced exercise",
abstract = "This study examined the influence of hyperthermia on middle cerebral artery mean blood velocity (MCA Vmean). Eleven cyclists undertook a 750kJ self-paced time trial in HOT (35°C) and COOL (20°C) conditions. Exercise time was longer in HOT (56min) compared with COOL (49min; P<0.001). Power output in HOT was significantly lower from 40{\%} of work completed onward (P<0.01). Rectal temperature increased to 39.6±0.6°C (HOT) and 38.8±0.5°C (COOL; P<0.01). Skin temperature, skin blood flow, and heart rate were higher throughout HOT compared with COOL (P<0.05). A similar increase in ventilation (P<0.05) and decrease in end-tidal partial pressure of CO2 (PETCO2; P<0.05) occurred in both conditions. Arterial blood pressure and oxygen uptake were lower from 50{\%} of work completed onward in HOT compared with COOL (P<0.01). MCA Vmean increased at 10{\%} in both conditions (P<0.01), decreasing thereafter (P<0.01) and to a greater extent in HOT from 40{\%} of work completed onward (P<0.05). Therefore, despite a comparable ventilatory response and PETCO2 in the HOT and COOL conditions, the greater level of thermal strain developing in the heat appears to have exacerbated the reduction in MCA Vmean, in part via increases in peripheral blood flow and a decrease in arterial blood pressure.",
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Heat stress exacerbates the reduction in middle cerebral artery blood velocity during prolonged self-paced exercise. / Périard, J. D.; Racinais, Sebastien.

In: Scandinavian Journal of Medicine and Science in Sports, Vol. 25, No. S1, 01.06.2015, p. 135-144.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Heat stress exacerbates the reduction in middle cerebral artery blood velocity during prolonged self-paced exercise

AU - Périard, J. D.

AU - Racinais, Sebastien

PY - 2015/6/1

Y1 - 2015/6/1

N2 - This study examined the influence of hyperthermia on middle cerebral artery mean blood velocity (MCA Vmean). Eleven cyclists undertook a 750kJ self-paced time trial in HOT (35°C) and COOL (20°C) conditions. Exercise time was longer in HOT (56min) compared with COOL (49min; P<0.001). Power output in HOT was significantly lower from 40% of work completed onward (P<0.01). Rectal temperature increased to 39.6±0.6°C (HOT) and 38.8±0.5°C (COOL; P<0.01). Skin temperature, skin blood flow, and heart rate were higher throughout HOT compared with COOL (P<0.05). A similar increase in ventilation (P<0.05) and decrease in end-tidal partial pressure of CO2 (PETCO2; P<0.05) occurred in both conditions. Arterial blood pressure and oxygen uptake were lower from 50% of work completed onward in HOT compared with COOL (P<0.01). MCA Vmean increased at 10% in both conditions (P<0.01), decreasing thereafter (P<0.01) and to a greater extent in HOT from 40% of work completed onward (P<0.05). Therefore, despite a comparable ventilatory response and PETCO2 in the HOT and COOL conditions, the greater level of thermal strain developing in the heat appears to have exacerbated the reduction in MCA Vmean, in part via increases in peripheral blood flow and a decrease in arterial blood pressure.

AB - This study examined the influence of hyperthermia on middle cerebral artery mean blood velocity (MCA Vmean). Eleven cyclists undertook a 750kJ self-paced time trial in HOT (35°C) and COOL (20°C) conditions. Exercise time was longer in HOT (56min) compared with COOL (49min; P<0.001). Power output in HOT was significantly lower from 40% of work completed onward (P<0.01). Rectal temperature increased to 39.6±0.6°C (HOT) and 38.8±0.5°C (COOL; P<0.01). Skin temperature, skin blood flow, and heart rate were higher throughout HOT compared with COOL (P<0.05). A similar increase in ventilation (P<0.05) and decrease in end-tidal partial pressure of CO2 (PETCO2; P<0.05) occurred in both conditions. Arterial blood pressure and oxygen uptake were lower from 50% of work completed onward in HOT compared with COOL (P<0.01). MCA Vmean increased at 10% in both conditions (P<0.01), decreasing thereafter (P<0.01) and to a greater extent in HOT from 40% of work completed onward (P<0.05). Therefore, despite a comparable ventilatory response and PETCO2 in the HOT and COOL conditions, the greater level of thermal strain developing in the heat appears to have exacerbated the reduction in MCA Vmean, in part via increases in peripheral blood flow and a decrease in arterial blood pressure.

KW - Cardiovascular strain

KW - Cerebral blood flow

KW - Cycling time trial

KW - Fatigue

KW - Hyperthermia

KW - Pacing

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DO - 10.1111/sms.12379

M3 - Article

VL - 25

SP - 135

EP - 144

JO - Scandinavian Journal of Sports Sciences

JF - Scandinavian Journal of Sports Sciences

SN - 0905-7188

IS - S1

ER -