TY - JOUR
T1 - Thermal drive contributes to hyperventilation during exercise in sheep
AU - Entin, Pauline L.
AU - Robertshaw, David
AU - Rawson, Richard E.
PY - 1998/7
Y1 - 1998/7
N2 - The etiology of exercise hypocapnia is unknown. The contributions of exercise intensity (ExInt), lactic acid, environmental temperature, rectal temperature (T(re)), and physical conditioning to the variance in arterial CO2 tension (Pa(CO2)) in the exercising sheep were quantified. We hypothesized that thermal drive contributes to hyperventilation. Four unshorn sheep were exercised at ~30, 50, and 70% of maximal O2 consumption for 30 min, or until exhaustion, both before and after 5 wk of physical conditioning. In addition, two of the sheep were shorn and exercised at each intensity in a cold (<15°C) environment. Tre and O2 consumption were measured continuously. Lactic acid and Pa(CO2) were measured at 5- to 10- min intervals. Data were analyzed by multiple regression on Pa(CO2). During exercise, T(re) rose and Pa(CO2) fell, except at the lowest ExInt in the cold environment. T(re) explained 77% of the variance in Pa(CO2), and ExInt explained 5%. All other variables were insignificant. We conclude that, in sheep, thermal drive contributes to hyperventilation during exercise.
AB - The etiology of exercise hypocapnia is unknown. The contributions of exercise intensity (ExInt), lactic acid, environmental temperature, rectal temperature (T(re)), and physical conditioning to the variance in arterial CO2 tension (Pa(CO2)) in the exercising sheep were quantified. We hypothesized that thermal drive contributes to hyperventilation. Four unshorn sheep were exercised at ~30, 50, and 70% of maximal O2 consumption for 30 min, or until exhaustion, both before and after 5 wk of physical conditioning. In addition, two of the sheep were shorn and exercised at each intensity in a cold (<15°C) environment. Tre and O2 consumption were measured continuously. Lactic acid and Pa(CO2) were measured at 5- to 10- min intervals. Data were analyzed by multiple regression on Pa(CO2). During exercise, T(re) rose and Pa(CO2) fell, except at the lowest ExInt in the cold environment. T(re) explained 77% of the variance in Pa(CO2), and ExInt explained 5%. All other variables were insignificant. We conclude that, in sheep, thermal drive contributes to hyperventilation during exercise.
KW - Blood gases
KW - Hyperthermia
KW - Hypocapnia
KW - Respiratory alkalosis
KW - Respiratory control
KW - Thermoregulation
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U2 - 10.1152/jappl.1998.85.1.318
DO - 10.1152/jappl.1998.85.1.318
M3 - Article
C2 - 9655792
AN - SCOPUS:0031827562
SN - 8750-7587
VL - 85
SP - 318
EP - 325
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 1
ER -