According to a study published in 2007(1), it was found that 3 weeks of post-exercise sauna bathing produced a worthwhile enhancement of endurance running performance and increased run time to exhaustion by 32%, which is equivalent to an enhancement of approximately 1.9% (1.3-2.4%) in an endurance time trial. The study authors attributed this significant improvement in endurance to the increased blood volume resulting from the three weeks of exposure to a very hot sauna (i.e., approximately 90 degrees C.) for about one half hour.
The study hypothesis was that physiological adaptations to sauna bathing could enhance endurance performance. A cross-over study was designed in which six male distance runners completed 3 weeks of post-training sauna bathing and 3 weeks of control training, with a 3 week washout. During the sauna period, study subjects sat in a humid sauna at 89.9+/-2.0 degrees C (mean+/-standard deviation) immediately post-exercise for 31+/-5 min on 12.7+/-2.1 occasions. The performance test was a treadmill run of approximately 15 minutes to exhaustion at the runner’s current best speed over 5 km. The test was performed on the 1st and 2nd day following completion of the sauna and control periods, and the times were averaged. Plasma, red-cell and total blood volume were measured via Evans blue dye dilution immediately prior to the first run to exhaustion for each period.
The study results showed, relative to control, tht sauna bathing increased run time to exhaustion by 32% (90% confidence limits 21-43%), which is equivalent to an enhancement of approximately 1.9% (1.3-2.4%) in an endurance time trial. Plasma and red-cell volumes increased by 7.1% (5.6-8.7%) and 3.5% (-0.8% to 8.1%) respectively, after sauna relative to control. Change in performance had high correlations with change in plasma volume (0.96, 0.76-0.99) and total blood volume (0.94, 0.66-0.99), but the correlation with change in red cell volume was unclear (0.48, -0.40 to 0.90). We conclude that 3 wk of post-exercise sauna bathing produced a worthwhile enhancement of endurance running performance, probably by increasing blood volume.
(1). Scoon, G. S., Hopkins, W. G., Mayhew, S. & Cotter, J. D. Effects of post-exercise sauna bathing on the enduranceperformance of competitive male runners. Journal of science and medicine in sport / Sport Medicine Australia 10, 259-262, (2007)