The influence of gender and menstrual phase on thermosensitivity during cold water immersion

Background: This investigation evaluated the influence of gender and phase of menstrual cycle (follicular (FOL: days 2-6) and luteal (LUT: days 19-24) phases) on thermosensitivity and metabolic heat production (HP) during col d water immersion (20 degrees C) in 10 females (22.4 +/- 2.8 yr) and 16 mal es (22.4 +/- 2.9 yr). Methods: Following a 20-min baseline period (BASE), s ubjects were immersed until esophageal temperature (Tes) reached 36.5 degre es C or for a maximum pre-occlusion (Pre-OCC) time of 40 min. An arm and th igh cuff Were then inflated to 180 and 220 mmHg, respectively, for 10 min ( OCC). Following release of the inflated cuffs (Post-OCC), the slope (beta) of the relationship between the decrease in Tes and the increase in HP was used to quantify thermosensitivity. Results: ANOVA revealed no significant difference in thermosensitivity between phases of the menstrual cycle or be tween men and women (FOL = -2.76, LUT = -3.05, Malts = -3.24 W . kg(-1) . d egrees C-1). A significant (p < 0.05) main effect for gender for HP, and a significant (p < 0.05) main effect for menstrual phase for mean skin temper ature (T-sk) Were observed. Conclusions: These data suggest, despite gender differences in HP, that the thermosensitivity of HP during cold water imme rsion is similar between males and females and is not influenced by menstru al cycle phase. Therefore, these data indicate that when faced with a cold challenge, women respond similarly to men in both phases of their menstrual cycle.