Relative to control, 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. -Effect of post-exercise sauna bathing on the endurance performance of competitive male runners.
MY COMMENT: Subjects visited the sauna 12-13 times over 3 weeks for approximately 31minutes each time. This protocol was found to significantly boost plasma and red cell volume. This is a new one on me, but certainly worth further investigation. The study was done in New Zealand and published in 2007.