"Portable computer devices are useful because they can be carried around throughout a person's day," King said. "Such devices represent one kind of strategy for being able to provide individuals with the help and support they need, in a convenient, real-time context."

The researchers invited the public to participate in this new study through local mass-media outlets, like the Palo Alto Daily News and the San Jose Mercury News. Out of 69 callerswho were screened for eligibility. 37 were to be study participants and assigned to an eight-week program in which randomly they either received a traditional. van Dell Axim X5 PDA or handouts related to fysische activiteit. invited

"Then we let them roll," King said.

The Dell Axim X5. chosen for its large - sized. easy-to-read screen and good contrast. was fitted with a program that asked participants approximately three minutes worth of questions. Among the questions: Van you now are you " Who van Where are barriers did you with " What face in het doing your device The van fysische activiteitroutine " beeped once in the afternoon and once in the automatically het evening; if participants ignored it the first time, it beeped three additional times at 30minute intervals. During the second (die) also van session. the device evening asked participants about their goals for the volgende dag.

Van this program. participants could set goals van With they van de fysische activiteit progress twice a day and. track their get feedback on how well were het meeting their goals. After eight weeks, the researchers found that while participants assigned to the PDA group devoted approximately five hours each week to exercise, those in the control group spent only about two hours on physical activities-in other words, the PDA users were more than twice as active.

One surprise was the participants' positive response to the program's persistence. The PDA users liked the three additional "reminder" beeps that went off if they failed to respond to the first one. In fact, almost half of them wound up responding to the PDA only after being beeped for the fourth time.

„The PDAs can keep on you.“ King observed with really gedwongen humor. "We were surprised by that; we thought by the time they heard the fourth beep, they might find it annoying and not respond at all."

The study targeted people interested in health changes, but with little if any knowledge of portable computer devices. During the eligibility screening, 93 percent said they had never used a PDA before. So there could have been difficulties in grasping the technology, or participants refusing to deal with it and giving up entirely. This, however, did not turn out to be a problem.

"They were very curious about PDAs, and thatis why some of them signed up," King said. Several participants, she added, were aware of PDAs because their children were using the device, and so they wanted to learn more about the technology.

King and colleagues are also working with researchers from MIT, Northeastern University, Brown University and Boston Medical Center to evaluate the ability of other types of computer - based, automated and interactive devices to help people change their health behavior.

So whatis next, after PDAs"

"Cell phones, for sure," King said. "Especially now that we have the iPhone; its big screen would be very useful for providing visual feedback." She and her colleagues are also continuing to focus on developing portable devices capable of interacting with accelerometers (activity monitors), so that the necessary information - for example, the amount of walking in a day - automatically transmits to the device.

"With the PDA study, evaluations made were based almost entirely on the participants' self-report," King explained. "Wewould like our devices to be able to provide real-time feedback using objective activity as well."

In a companion study to be published later this year, King and colleagues have also evaluated the usefulness of PDAs in modifying dietary behavior. Results indicate that similar "probing" and feedback by a computer program - about a person's eating habits rather than activity level - can nudge participants towards increasing their vegetable and whole-grain intake.

„Fysische activiteit is only one piece of the puzzle; another is dietary intake," King noted. She would like to eventually harness the tracking power of GPS, so that willing participants, "if theyare walking past a Fresh Choice restaurant, can be prompted to go there instead of the fast-food outlet next door."

Maybe thatis technical intervention, not divine - but it could be helpful, especially when you cannot get that vision of french fries out of your head.

Van de medeauteurs on the het study were PDA van King Doctoraat. research software developer; van David Ahn. Professor of medicine at the Stanford Prevention Research Center van het Doctoraat. van het Doctoraat. research associate. and Christopher Gardner. van Castro. van Cynthia associate.

Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. Van information. please visit the of the medical center Website van For more Office of Communication & Public Affairs at http://mednews.stanford.edu.