Keen

Tattoos may permanently alter the physiology of skin in ways that affect sweating. According to a small, new study, the amount and saltiness of sweat change after skin has been dyed, a finding that might have implications for athletes who ink large swaths of their bodies and maybe even for those of us who sport one or two discreet tattoos (such as the small one on my right shoulder, in case you were wondering). Tattoos are decorative, often metaphoric, sometimes regrettable, but always injurious. To create a tattoo, the artist punctures the skin with dye-filled needles at a rate of up to 3,000 times per minute. The dye is injected into the skin’s dermal layer, which is also where most sweat glands are. The body recognizes these injections as abnormal. They have slightly damaged the tissue and left behind a foreign substance, the ink. So the immune system gears up, sending a variety of cells to the site of the inking. Some cells carry off tiny amounts of the ink, primarily to

Practicing tai chi helps older people improve their balance and avoid falls, a review of studies has found. Tai chi is a form of Chinese martial arts now practiced as exercise. It involves a specific program of graceful movements, accompanied by deep breathing and mental focus, that slowly move the center of balance from one leg to the other. Researchers found 10 randomized trials analyzing the effect of tai chi on the incidence of falls or the time until an elderly person first has a fall. All studies compared tai chi to usual care or other treatments like physical therapy, stretching or exercise. The analysis, in the Journal of the American Geriatric Society, found that tai chi reduced the incidence of falls by 43 percent in those followed for less than a year and by 13 percent in those followed longer. There was no effect of tai chi on time to first fall, and there was some weak evidence that the practice reduced the number of falls that resulted in injury. Falls are a le