What Doesn't Kill Us

by Scott Carney

To stave off hypothermia, the body conserves heat by shutting off blood supply to the extremities. When this happens, miles of vestibular roadways squinch closed, keeping most of the blood in the body’s core and letting the vital organs relax in a warm blood cocoon while temperatures in the hands, feet, ears, and nose plummet. The colder it is outside, the stronger the response. For a person not regularly conditioned to temperature shifts, vasoconstriction is painful. The only way that most of us can trigger the muscle response is to actually go outside and feel the cold. And those of us who live in perpetually climate-controlled environments never exercise this part of our circulatory system. Weak circulatory muscles are a side effect of living in a very narrow band of temperature variation. The vast majority of humanity today—the entire population that spends the bulk of its time indoors and/or whose only experience when it gets too cold or too hot is wearing state-of-the-art outdoor gear—never exercises this critical system of their body. Even people who appear physically fit, with lean muscles and chiseled abs, might be secretly hiding weak circulatory muscles. And the stakes are huge: In the long run, circulatory diseases contribute to almost 30 percent of the world’s mortality.