Control of sweating during the human menstrual cycle

Thermoregulatory responses were studied in seven women during two separate experimental protocols in the follicular (F, days 4–7) phase and during the luteal (L, days 19–22) phase of the menstrual cycle. Continuous measurements of esophageal temperature (T _es), mean skin temperature ( \(\dot T_{sk} \) ), oxygen uptake and forearm sweating ( \(\dot m_s \) ) were made during all experiments. Protocol I involved both passive heat exposure (3 h) and cycle exercise at ∼80% \(\dot V_{o_2 } \) peak during which the environmental chamber was controlled atT _a=50.0° C, rh=14% (P _w=1.7 kPa). In protocol II subjects were tested during thirty-five minutes of exercise at ∼85% \(\dot V_{o_2 } \) peak atT _a=35° C and rh=25% (P _w=1.4 kPa). The normal L increase in restingT _es (≈0.3° C) occurred in all seven subjects. \(\dot T_{sk} \) was higher during L than F in all experiments conducted at 50° C. During exercise and passive heat exposure, theT _es threshold for sweating was higher in L, with no change in the thermosensitivity (slope) of \(\dot m_s \) toT _es between menstrual cycle phases. This rightward or upward shift inT _es threshold for initiation of sweating averaged 0.5° C for all experiments. The data indicate the luteal phase modulation in the control of sweating in healthy women is also apparent during severe exercise and/or heat stress.