LAUSR

Purpose This study investigated whether intermittent post-exercise sauna bathing across three-weeks endurance training improves exercise heat tolerance and exercise performance markers in temperate conditions, compared to endurance training alone. The subsidiary aim was to determine whether exercise-heat tolerance would further improve following 7-Weeks post-exercise sauna bathing. Methods Twenty middle-distance runners (13 female; mean ± SD, age 20 ± 2 years, $$V$$ V O 2max 56.1 ± 8.7 ml kg −1  min −1 ) performed a running heat tolerance test (30-min, 9 km h −1 /2% gradient, 40 °C/40%RH; HTT) and temperate (18 °C) exercise tests (maximal aerobic capacity [ $$V$$ V O 2max ], speed at 4 mmol L −1 blood lactate concentration ([La − ]) before (Pre) and following three-weeks (3-Weeks) normal training (CON; n  = 8) or normal training with 28 ± 2 min post-exercise sauna bathing (101–108 °C, 5–10%RH) 3 ± 1 times per week (SAUNA; n  = 12). Changes from Pre to 3-Weeks were compared between-groups using an analysis of co-variance. Six SAUNA participants continued the intervention for 7 weeks, completing an additional HTT (7-Weeks; data compared using a one-way repeated-measures analysis of variance). Results During the HTT, SAUNA reduced peak rectal temperature ( T rec ; − 0.2 °C), skin temperature (− 0.8 °C), and heart rate (− 11 beats min −1 ) more than CON at 3-Weeks compared to Pre (all p  < 0.05). SAUNA also improved $$V$$ V O 2max (+ 0.27 L −1  min −1 ; p  = 0.02) and speed at 4 mmol L −1 [La − ] (+ 0.6 km h −1 ; p  = 0.01) more than CON at 3-Weeks compared to Pre. Only peak T rec (− 0.1 °C; p  = 0.03 decreased further from 3-Weeks to 7-Weeks in SAUNA (other physiological variables p  > 0.05). Conclusions Three-weeks post-exercise sauna bathing is an effective and pragmatic method of heat acclimation, and an effective ergogenic aid. Extending the intervention to seven weeks only marginally improved T rec .