Post-exercise sauna

Exposure to heat is widely used as a traditional therapy in many different cultures but does it really have the benefits we would associate with it (improved circulation, stronger heart, etc.)? I recently came across some old (2001, 2004 and 2006) medical papers on the benefits of saunas - the first looked at the benefits to patients with coronary risk factors, the second at how regular sauna use reduces stress factors and the third at the effect of post-exercise sauna bathing on the endurance performance of athletes.

In the first study, 25 men with at least one coronary risk factor and 10 healthy men without coronary risk factors were enrolled. Patients in the risk group were treated with a dry sauna for 15 min and then kept in a bed covered with blankets for 30 min once a day for two weeks. They found that the repeated sauna treatment improves impaired vascular endothelial function in the setting of coronary risk factors, suggesting a therapeutic role for sauna treatment in patients with risk factors for atherosclerosis.

For the second paper, 28 subjects with at least one coronary risk factor participated in the study. They were randomly assigned to either the sauna group or the non-sauna group. As in the first study, subjects in the sauna group were placed supine in a dry sauna for 15 minutes. After the sauna, they rested on a bed with a blanket for 30 minutes. This occurred once a day for two weeks. Subjects in the non-sauna group were placed in supine position at room temperature for 45 minutes a day for two weeks.

The coronary risk factors measured were body weight, heart rate, blood pressure, hematocrit, total cholesterol, HDL cholesterol, triglycerides, fasting plama glucose and urinary 8-Epi-Prostaglandin F2a (a marker of oxidative stress). All subjects were admitted to the same hospital and ate the same meals throughout the two-week study period. On admission and after two weeks, urine samples were taken after an overnight fast.

Results of the study showed that repeated sauna therapy significantly reduces levels of urinary 8-Epi-Prostaglandin F2a, a marker of oxidative stress, or destruction caused by free radicals, which may lead to diseases such as atherosclerosis, cancer and Alzheimer’s disease, according to recent research. Systolic blood pressure in the sauna group had also decreased significantly after two weeks and it was significantly lower than that of the non-sauna group. The authors suggested a combination of diet, exercise and repeated sauna therapy as the best method for preventing lifestyle-related diseases, such as hypertension, hyperlipidemia and diabetes mellitus. The good news is that repeated sauna therapy can be used even for patients who are unable to exercise, e.g., due to injury.

I then wondered whether these beneficial effects could be used for improving athletic performance, which led me to find the third study (good old Google!). They performed a cross-over study in which six male distance runners completed three weeks of post-training sauna bathing and 3 weeks of control training, with a 3-week washout. During the sauna period, subjects sat in a humid sauna immediately post-exercise for 30 mins. The performance test was a 15-min treadmill run 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 immediately prior to the first run to exhaustion for each period. Relative to control, sauna bathing increased run time to exhaustion by 32%, which is equivalent to an enhancement of 1.9% in an endurance time trial. Plasma and red-cell volumes increased by 7.1% and 3.5% respectively, after sauna relative to control. Change in performance had high correlations with change in plasma volume and total blood volume, although the correlation with change in red-cell volume was unclear. They concluded that the physiological adaptations to 3 weeks of post-exercise sauna bathing produced a worthwhile enhancement of endurance running performance, probably by increasing blood volume.

So which is better - dry or humid sauna? Dry is where infrared rays are used to induce heat, whereas a humid sauna is either a hot steam room or the Finnish-style sauna where water is added to hot rocks to create a mist.

So I tracked down the results of yet another study, which compared changes in hemodynamic and thermoregulatory functions during 10 mins of humid sauna bathing and those in a dry sauna. Subjects were 7 healthy young men. Blood pressure, heart rate, skin temperature at chest, forearm, thigh, and leg, skin blood flow at forearm, and sweat rate were measured at 1-min intervals throughout the experiment. Total sweating and change of hematocrit were also measured for dehydration analysis.

Blood pressure and heart rate were higher and total sweating greater in dry bathing than humid. Mean skin temperature in dry bathing was higher than that in mist bathing, i.e., you feel the heat more on the skin than "in your bones". This suggests that the heat stress of the dry sauna may be stronger than that of the mist sauna, leading to dehydration by sweating. On the other hand, changes in skin blood flow and sweat rate during the mist sauna were increased much more than those during dry sauna. The mist sauna may thus be safer physiologically and provide more effective vascular dilation and sweating than the dry sauna.

In short, if you want decrease your risk of coronary disease, improve your athletic performance, your endurance and stamina or if you just want a good sauna - (a) it's good for you and (b) head for the humid kind (I must admit to never having seen the dry kind...)

References:

Repeated thermal therapy improves impaired vascular endothelial function in patients with coronary risk factors
Masakazu Imamura, Sadatoshi Biro, Takashi Kihara, Shiro Yoshifuku, Kunitsugu Takasaki, Yutaka Otsuji, Shinichi Minagoe, Yoshifumi Toyama and Chuwa Tei
J Am Coll Cardiol, 2001; 38:1083-1088

Repeated Sauna Therapy Reduces Urinary 8-Epi-Prostaglandin F2a
Akinori Masuda, Masaaki Miyata, Takashi Kihara, Shinichi Minagoe and Chuwa Tei
Japanese Heart Journal, 2004, Vol. 45, pp. 297-303.

Effect of post-exercise sauna bathing on the endurance performance of competitive male runners
Guy S.M. Scoona, William G. Hopkinsb, Simon Mayhewb and James D. Cottera
J Science and Medicine in Sport; Vol 10, Iss 4, Aug 2007, 259-262

Effects on changes in hemodynamic and thermoregulatory functions during mist and dry sauna bathing
Kawahara Yuko, Nagata Mayumi, Niimi Yuki, Miwa Chihiro, Iwase Satoshi
Autonomic Nervous System Journal, 2002, Vol 39, No 4, pp 402-408