Remember the 10,000 step a day rule? Forget it. This year’s model, created by researchers at the University of Glasgow, calls for 15,000 steps a day. But wait, the study authors point out that walking 15,000 steps would take about three and half hours, no problem if you happen to be a postman. Time magazine reports that one group of researchers arrived at the 15,000 step mark by counting the steps of some of the most heart-healthy people in the world, an isolated tribe in the Bolivian Amazon called the Tsimane. OK, the Tsimane spend five or six hours a day on their feet, a bit more than most of us can hope for. Another study that agreed on the 15,000 step guideline looked at postmen and found that those who took 15,000 steps or more each day had almost no cardiovascular disease. It also found that every extra hour that a postal worker spent sitting during a typical workday was linked to an additional .8 inches of waistline and a heart disease risk 0.2 percent greater. All of the researchers think we need to walk at least 5,000 steps a day. Yes, 7,500 is better, and yes, 10,000 is even better, and yes…….