During hyperthermia, venous blood from the face and scalp flows into the intracranium through the ophthalmic and emissary veins, which is supposed to be an important respons providing selective brain cooling in humans. To understand a possible mechanism of this response, healthy male volunteers were subjected to either passive body warming or exercise, in a climatic chamber whose air temperature and relative humidity were 28℃ and 40%.
　During either passive body warming or exercise, forehead sweat rate (msw) and forehead skin blood flow (Qsk) started to increase shortly after the start of heat loading. A rather abrupt increase of venous flow through the opthalmic veins into the intracranium occurred significantly later than the increases on msw and Qsk. Tympanic temperature at this abrupt increase in ophthalmic venous flow did not differ between the tests.
　Mean skin temperature at this flow increase was, however, significantly higher during passive body warming than in exercise. The abrupt increase of inward venous flow through the ophthalmic veins was not observed in nearly 20% of subjects. The reason for this inter-individual difference of this response is discussed.

DESCENTE SPORTS SCIENCE Vol.14/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE