Correlation and causation?
I’ve seen a number of links today to this Swedish study showing people who commute by bike are healthier (mentally and physically) than those who drive or take public transportation.
BMJ.com (nee the British Medical Journal) published a study today showing that a bike share program in Barcelona, Spain saves human lives while reducing greenhouse gas emissions. The benefits from increased physical activity far outweight the risks from increased exposure to traffic and air pollutants.
Recent research has shown that endurance athletes suffer cardiac fibrosis — scarring in the heart muscle. When scientists look at heart tissue from marathon runners, rowers and Ironman competitors, they often find signs of fibrosis, while sedentary subjects usually have no fibrosis at all. In non-athletes, fibrosis is an indicator for arythmias, but medical researchers don’t know how how this heart muscle fibrosis effects the longevity of endurance athletes.