Sex differences in adaptation to intermittent post-exercise sauna bathing in trained middle-distance runners

Background The purpose of this study was to investigate the effect of sex on the efficacy of intermittent post-exercise sauna bathing to induce heat acclimation and improve markers of temperate exercise performance in trained athletes. Methods Twenty-six trained runners (16 female; mean +/- SD, age 19 +/- 1 years, (V) over dotO(2max) F: 52.6 +/- 6.9 mL.kg(-1).min(-1), M: 64.6 +/- 2.4 mL.kg(-1).min(-1)) performed a running heat tolerance test (30 min, 9 km.h(-1)/2% gradient, 40 degrees C/40%RH; HTT) and temperate (18 degrees C) exercise tests (maximal aerobic capacity [(V) over dotO(2max)] and lactate profile) pre and post 3 weeks of normal exercise training plus 29 +/- 1 min post-exercise sauna bathing (101-108 degrees C) 3 +/- 1 times per week. Results Females and males exhibited similar reductions (interactions p > 0.05) in peak rectal temperature (- 0.3 degrees C; p < 0.001), skin temperature (- 0.9 degrees C; p < 0.001) and heart rate (- 9 beats.min(-1); p = 0.001) during the HTT at post- vs pre-intervention. Only females exhibited an increase in active sweat glands on the forearm (measured via modified iodine technique; F: + 57%, p < 0.001; M: + 1%, p = 0.47). Conversely, only males increased forearm blood flow (measured via venous occlusion plethysmography; F: + 31%, p = 0.61; M: + 123%; p < 0.001). Females and males showed similar (interactions p > 0.05) improvements in (V) over dotO(2max) (+ 5%; p = 0.02) and running speed at 4 mmol.L-1 blood lactate concentration (+ 0.4 km.h(-1); p = 0.001). Conclusions Three weeks of post-exercise sauna bathing effectively induces heat acclimation in females and males, though possibly amid different thermoeffector adaptations. Post-exercise sauna bathing is also an effective ergogenic aid for both sexes.

Automated summary

Intermittent post-exercise sauna bathing effectively induces heat acclimation in both male and female athletes, with potential differences in thermoeffector adaptations. Improvements in running speed at 4mmol.L-1 blood lactate concentration were observed in both sexes.