Table 4: Repeated sauna and athletes.

Study characteristics Study sample Intervention ComparatorsHealth effectsAdverse side effects
Author & yearLevel of evidenceDesignPop/countrySauna typeDurationComparator/
controls
Outcome
measures
Positive/negative/negligibleNone/mild/
moderate/
severe

2015
Stanley et al. [61]
IIISingle-group,
interrupted time series study
Elite Athletes–
Males/
Australia
7Finnish10 daysNo control groupPlasma volume changes (calculated from Hb readings); hydration status (using urine SG by digital refractometer);
ergometer exercise performance measures; HRV
Positive,
postexercise sauna bathing increased plasma volume after 4 days of intervention ()
Mild
comments of “hot and very uncomfortable, but tolerable” per thermal comfort survey conducted every 5 min during sauna sessions

2012
Zinchuk and Zhadzko [62]
IIISingle-group interventional studyMale Elite Athletes/
Belarus
16Finnish5 monthsNo control groupAxillary temp; venous blood gas analysis; lipid peroxidation and free radical processes by UV and fluorescence analysis of plasma and RBCs; antioxidant estimation by α-tocopherol fluorescence analysis of plasma and RBC catalase activity; nitric oxide metabolism by spectrophotometric methods, plasma nitrate and nitrite levelsPositive, increased axillary body temp 2.6°C () after first sauna and 1.9°C () after course of sauna; increased pH by 0.8% (), decreased base excess by 20.3% (), increased venous O2 by 53.3% (), increased Hb concentration in blood by 5.2% (), right shift of oxy-Hb dissociation curve (decreased affinity – favours release of O2 to tissues) after 1st sauna; similar changes after final sauna ()None

RH = relative humidity; Hb = haemoglobin; SG = specific gravity; HRV = heart rate variability; temp = temperature; O2 = oxygen; ROS = reactive oxygenated species; RBCs = red blood cells or erythrocytes.