Elements

Our ancestors spent most of their time out in the elements exposed to extremes of hot and cold. Joshua Slocum, the first man to sail solo around the world, observed that the natives of Tierra del Fuego were actually sweating while almost naked in freezing temperatures.  Cold exposure has been shown to increase metabolism, reduce inflammation, increase insulin sensitivity, and improve circulation, sleep and recovery.  At the other extreme, studies of Finnish sauna users showed they had lower incidences of heart disease and all cause mortality.