Inoue Yoshimitsu, Tanaka Yoshiko, Omori Kaori, Kuwahara Tomoko, Ogura Yukio, Ueda Hiroyuki
Laboratory for Human Performance Research, Osaka International University, 6-21-57 Tohda-Cho, Moriguchi, Osaka 570-8555, Japan.
Eur J Appl Physiol. 2005 Jun;94(3):323-32. doi: 10.1007/s00421-004-1303-2. Epub 2005 Feb 24.
To examine sex- and menstrual cycle-related differences in thermoregulatory responses to heat exposure, ten young women and six young men were heated passively by immersing their legs in water heated to 42 degrees C for 60 min (in ambient conditions of 30 degrees C and 45% relative humidity). The women underwent heat exposure during the mid-follicular (F) and mid-luteal (L) phases of the menstrual cycle, which were confirmed by assaying plasma female reproductive hormones. The rectal and mean body (T(b)) temperatures of women in the L phase were significantly greater than those of women in the F phase and of men during a pre-heating equilibration period (28 degrees C) and during heat exposure. During heat exposure, the local sweat rates (m(sw)) on the forehead, chest, back, and forearm of women in either phase were significantly lower than those of men, but the thigh (m(sw)) was similar to that of men. The m(sw) did not change at any site during the different phases of the menstrual cycle. The cutaneous blood flow (%LDF) was significantly greater on the thigh for women in either phase compared with men, but no difference was found at any other site (forehead, chest, back, and forearm). The %LDF on the back was significantly greater for women in the L phase than in the F phase, but those at other sites were similar in both phases. We conclude that, compared with men, heat loss from women depends more on cutaneous vasodilation (especially on the thigh) than on sweating, irrespective of the phase of the menstrual cycle. This phenomenon was due to peripheral mechanisms, as reflected in the greater slope of the relationship between %LDF and T(b) lower slope of the relationship between m(sw)) and frequency of sweat expulsion, and lower sweat output per gland. The menstrual cycle modified the T(b) threshold for vasodilation and sweat onset in women. Therefore, the sex difference in the T(b) threshold was more marked for women during the L phase than during the F phase. Moreover, the menstrual cycle modified the slope of the relationship between %LDF on the back and T(b).
为研究热暴露时体温调节反应的性别差异及与月经周期的关系，将10名年轻女性和6名年轻男性的双腿浸入42℃的热水中60分钟（环境温度30℃，相对湿度45%）进行被动加热。女性在月经周期的卵泡中期（F）和黄体中期（L）接受热暴露，通过检测血浆女性生殖激素予以确认。在预热平衡期（28℃）和热暴露期间，L期女性的直肠温度和平均体温（T(b)）显著高于F期女性和男性。热暴露期间，两个阶段女性的前额、胸部、背部和前臂局部出汗率（m(sw)）均显著低于男性，但大腿部（m(sw)）与男性相似。月经周期不同阶段，各部位的m(sw)均无变化。两个阶段女性大腿部的皮肤血流量（%LDF）均显著高于男性，但在其他部位（前额、胸部、背部和前臂）未发现差异。L期女性背部的%LDF显著高于F期，但其他部位在两个阶段相似。我们得出结论，与男性相比，无论月经周期处于哪个阶段，女性散热更多依赖皮肤血管舒张（尤其是大腿部）而非出汗。这种现象是由外周机制引起的，表现为%LDF与T(b)之间关系的斜率更大、m(sw)与排汗频率之间关系的斜率更低以及每个汗腺的出汗量更低。月经周期改变了女性血管舒张和出汗开始的T(b)阈值。因此，女性在L期的T(b)阈值性别差异比F期更明显。此外，月经周期改变了背部%LDF与T(b)之间关系的斜率。
