Thermoregulatory sweating during light exercise during cold air temperature transients was examined in women at two different phases of their menstrual cycle. Nine women with normal menstrual cycles participated (age=27.2±4.5 y; DuBois Surface Area=1.6±0.1 m
2; % Body Fat=20.0±3.8%; heart rate maximum=195±6.1 beats·min
−1, and V
O2,max=46.2±4.4 mL·kg
−1 min
−1). Experiments were conducted in the late fall, winter, and early spring at the same time of day (0700–0900 h). The women were studied in their early follicular (F) and mid-luteal (L) phases clothed in fatigues+Goretex
TM parka during treadmill exercise (∼34% V
O2,max). Air temperature (T
a) was decreased from an initial level of 20°C/40% RH to −5.0°C (wind speed of 1 m·s
−1) at a rate of −0.3°C·min
−1 over 80 min. Esophageal (T
es), mean skin (T
sk) and upper arm (T
arm) temperatures, V
O2, and arm sweating rate (m
sw) were recorded continuously. For the first 40 min of exercise, m
sw was correlated with T
es (r
2=0.66 in F and 0.75 in L) but became inhibited by cold T
sk during the final 40 min. Throughout the exercise/cold transient, m
sw was higher (P<0.05) and T
es threshold temperature was increased by 0.35°C in the L vs F. Sudomotor control was adequately predicted using a maximum likelihood estimation model combining T
es, T
sk and T
arm. The model confirmed that the m
sw is a function of T
es, T
sk & T
arm, increases by 22% (P<0.05) as T
es threshold is displaced upwards in the L phase. In conclusion, sweating rates in the F and L during light exercise are influenced separately by changes in skin cooling and may be highly responsive to perturbations in hormonal balance.
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