As a lifelong endurance runner, a marathon a year for 43 consecutive years (Boston 2013), I am eager to know the deep science behind the universal value that physical exercise is good, its lack bad, for everything. The heart and arteries, the lipids and the sugars, the bones and the muscles, the brain and nerves all obey the cosmic dictum " use it or lose it." I have described the adverse effects that inactivity applies to every corner of the body as "The Disuse Syndrome."(1)
Since the effect is so widespread its causative mechanism cannot be confined to just a single point, the whole body system must be involved. Not just one organ or just one gene but all. To a great extent all of our structure and function are similar. We are all made of the same kind of flesh and play by the same biochemical metabolic rules. What differentiates us therefore is not the cards we are dealt so much as the way we play the hand. The genes are the switches that direct our performance. They are differentially activated like a rheostat, not simply on or off, but react quantitatively to their environment. This function goes by the name of "epigenesis." How the environment affects the genes is critical, their expression. We recognize that one of the active issues concerning gene expression is temperature, the specific gene aromatase, affects turtle sex. It is precisely cued by temperature. If conception occurs when it is hot the turtle becomes male, if cool it becomes female.
Knowing this I have proposed that maybe the reason that exercise is such a universal good is "hot mitochondria." The mitochondria are micro batteries in all of cells, and thus are heated up by exercise. The mitochondria, thus warmed, could prompt a general systemic benefit.
As I have cast about this hypothesis several insightful people commented, "Okay, if the mitochondria are the real ticket, what about other ways of heating them up, such as sauna?" I shrugged in ignorance.
Now in the April 2015 issue of JAMA is an article from Eastern Finland entitled "Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality." (2) The article surveyed 2,315 middle-aged men, aged 42 to 60.The group was followed for 20.7 years. With virtually no exceptions all used the sauna. Their use, frequency and duration, were then compared to various clinical events. There were 929 deaths.
The authors conclude, "increased frequency of sauna bathing is associated with a reduced risk of sudden cardiac death, of fatal coronary heart disease, fatal cardiovascular disease, and all cause mortality. The reduced risk was quantitatively related to the time spent in the sauna."
"Hot mitochondia" confirmed? Maybe.
References
1)Bortz, W. The Disuse Syndrome 1984;
Western J. Medicine 141:691-694.
2) Laukkanen,T. et al Association Between Sauna Bathing and Fatal Cardiovascular and All -Cause Mortality JAMA 2015; 175:542-548.