The Global Positioning Device, or GPS, is a wonderful invention for helping to stop people from getting lost, whether they're on foot, in the mountains, or just driving. Now French physicians have reported a new use in the journal Circulation. Patients with peripheral arterial disease, or PAD, have clogged leg arteries that cause calf pain when walking; this is called intermittent claudication. In order to determine the severity of the condition, and to measure progress under treatment, physicians use what's termed the maximal walking distance, or MWD.

The MWD usually measured on a treadmill. However, the French doctors felt that a more natural way would be to let the patients walk unconstrained in a public park with their distance measured by GPS . There were 24 patients in the study - 6 women and 18 men, with an average age of 57. The MWD measured with GPS was compared with the self-reported MWD by the patient, that obtained by a treadmill test, and the distance obtained from a Walking Impairment Questionnaire. The GPS method offered the nearest result to that obtained from the treadmill test.

There are disadvantages to the GPS method. During a treadmill test other measurements are made - blood pressure, oxygen consumption, and heart rate. However, not every doctor has a treadmill, whereas a GPS is quite cheap. And a walk in the park is certainly more natural than on a treadmill ...