We've heard it before, but it bears repeating. The simple act of walking may be one of the very best things you can do for your health. In two recent studies, Janet Wallace, IU Bloomington professor of kinesiology at the IU School of Health, Physical Education and Recreation, and IU colleagues have shown that physical activity, especially walking, can protect arteries and lower blood pressure.

In a study published in the European Journal of Applied Physiology , Wallace and her co-authors looked at the “postprandial” state we find ourselves in after a full fatty meal. In that state, our arteries lose their ability to expand in response to blood flow, a key factor involved in atherosclerotic heart disease.

After a fat-filled meal, “your artery looks just like the artery of a person who has heart disease,” says Wallace. “What our study showed is that if you exercise after that meal, it doesn't look like a sick artery anymore.”

In the study, 25-year-olds walked on a treadmill for 45 minutes two hours after eating either a high-fat breakfast (eggs, sausage, and hash browns, with 48 grams of fat) or a breakfast of similar calories but no fat. Physical activity after the high-fat meal not only counteracted the dysfunction caused by fatty foods but also improved the function of the same arteries as compared to before the meal. “Results from this study suggest that physical activity may be effective in reversing the adverse vascular effects observed following the consumption of a high-fat meal,” says lead author Juame Padilla, a doctoral student in IU's kinesiology department. Other co-authors include Alyce Fly, IU associate professor of applied health science, kinesiology doctoral student Ryan Harris, and Lawrence Rink, clinical professor at the IU School of Medicine.

Wallace and Rink also co-authored (with doctoral student Saejong Park) a second recent study showing that four short, brisk walks a day can be more helpful to people watching their blood pressure than an extended exercise session. Wallace compared the effect of accumulated physical activity on elevated blood pressure versus the effect of continuous physical activity. Participants with prehypertension, or elevated blood pressure, walked on a treadmill continuously for 40 minutes one day, then four times for 10 minutes over the course of 3.5 hours on the next day. Both forms of exercise decreased participants' blood pressure, but the effect lasted 11 hours in the 10-minute walkers group, compared to seven hours for those who walked continuously.

“We had no idea the short bouts would be better,” Wallace says. “Most studies report the long continuous sessions as more effective.” Wallace's findings are particularly significant because uncontrolled high blood pressure can increase a person's risk for heart attack, heart failure, kidney failure, stroke, and blindness. More than 45 million people in the United States are estimated to have prehypertension, which is treated only with diet and exercise. More people may be able to fit crucial exercise into their days, Wallace points out, if they're aware that short bouts of 10 minutes are beneficial.

But what paths will those walkers take when they hit the outdoors? It depends. In a study of group behavior published in the journal Complexity , Robert Goldstone, director of IU Bloomington's Cognitive Science program and of the Percepts and Concepts Laboratory, and graduate student Michael Roberts created a virtual environment in which a group of 302 IU undergraduates were instructed to travel from city to city while minimizing travel costs and earning the most points possible. Travel costs for each patch of the virtual environment were related to how many times the patch was visited by others, decreasing the more it was trodden, so the participants were motivated to take advantage of paths created by others' digital steps. Points were awarded for each destination reached, but lost for every step taken.

The trails created by the participants were compromises between people making a beeline path directly to their destinations and taking well-established paths where people had already traveled, say the co-authors. A set of paths that connects a set of points, or destinations, using the minimal amount of path length is called a Minimal Steiner Tree (MST). Soap films frequently create MST configurations, but humans do not, according to Goldstone and Roberts. However, the virtual paths created by students in the study did deviate from beeline paths in the direction of MSTs.

Understanding the dynamics of path formation among human groups has applications well beyond knowing where to create sidewalks. “The potential promise of this work is that similar processes are involved in concrete and abstract collective path formation,” say the co-authors. For example, such processes may extend researchers' understanding of multirobot cooperation or robustly interacting software systems. “The growth of our collective spatial path systems,” Goldstone and Roberts say, “may reveal principles about how future progress is more generally achieved by exploiting and extending prior innovations.”