Step activity monitor: Long-term, continuous recording of ambulatory function

In many areas of research and medicine, objective data describing an indivi dual's ambulatory function are sought as useful indicators of that person's condition. Normally, detailed measurements are taken over short periods of time within a controlled laboratory setting. To complement this approach, Prosthetics Research Study has developed a small, unobtrusive instrument th at continuously records a simple measure-step counts per unit time-as an in dividual goes about normal daily life. The Step Activity Monitor (SAM) is a pproximately the size and weight of a pager and is worn at: the ankle. It c an detect steps with better than 99% accuracy across a wide range of gait s tyles for adults, children, and large animals. During monitoring, step coun ts are recorded at consecutive, adjustable time intervals over weeks to mon ths at a time. Recording at 1-min intervals for a minimum of 2 weeks is rec ommended. Once monitoring is completed, the data are transferred to a compu ter, and the levels and patterns of step activity can be analyzed. This art icle provides a detailed description of the SAM, guidelines for use, result s of accuracy and reliability testing, case study descriptions demonstratin g the ability to measure differences that result from medical interventions or changes in health status, and a discussion of considerations pertinent to long-term monitoring of activity.