BG Steele, VA Puget Sound Health Care System; B Belza, University of Washington School of Nursing; L Holt, VA Puget Sound Health Care System; J Hunziker, University of Washington School of Nursing; S Lakshminaryan, VA Puget Sound Health Care System; DM Buchner, Division of Nutrition and Physical Activity, National Centers for Disease Control and Prevention, CDC

Objectives: Although there are numerous measures that tap the varied dimensions of functional status, the ability to accurately measure everyday "free-living" physical activity remains elusive. The objective of this investigation was to evaluate the performance of a motion sensor, the TriTrac-R3D accelerometer (Reining International, Inc.), as a process measure of free-living activity and exercise in COPD outpatients.

Methods: A prospective, pre, post-test design was used. Forty-one male outpatients with stable COPD (mean age 66, mean forced expiratory volume in one second, percent predicted, 36) were studied prior to beginning (Time 1) and during the seventh week (Time 2) of an eight-week pulmonary rehabilitation program. Subjects wore the TriTrac-R3D for four days, but only 24 hours of data was used in this analysis. Three subjects were excluded because they wore the device fewer than five hours. The accelerometer is the size of a cellular phone worn at the waist that measures movement in three dimensions and integrates these signals as vector magnitude units (VMU), a raw indicator of movement. The device provides a computer interface with graphical and numerical data display, treatment, and storage. Vector magnitude per minute (VMU/min.) was calculated by dividing the total 24-hour VMU by total minutes worn. Data analysis included descriptive statistics and a paired, two-tailed t-test of VMU/min. at Times 1 and 2 with significance set at p<.05. A power estimate with sample size of 38 was .90. Visual inspection of graphed VMU output data was also used to identify periods of exercise at Time 2.

Results: The mean value for Time 1 VMU/min. was 87.4; standard deviation was 38.8. The mean and standard deviation for Time 2 VMU/min. was 115.2 and 59.4, respectively. A two-tailed, paired t-test of the difference in VMU/min. at Times 1 and 2 was carried out in 38 subjects (t=-3.46; p<.01). Visual inspection of the graphical accelerometer output for Thursday Time 2 demonstrated exercise on both the treadmill and Nustep.

Conclusions: The crafting of process and outcome measures is a concern among investigators interested in human performance. These findings suggest that a triaxial accelerometer can differentiate physical activity levels prior to and during an exercise program. Exercise was also recognized graphically. The device was well accepted by chronically ill subjects. Accelerometer measurement of everyday, "free-living" physical activity is an innovative strategy to measure a key dimension of functional status not previously well quantified.

Impact: This methodology has potential utility as a process and outcome measure in VA clinical settings, including decision-making in provision of durable medical equipment, clinical needs assessment, treatment, and research. A more recent modification of the TriTrac-R3D technology, the RT3 (Stay Healthy, Inc.), incorporates an event marker, making it easier to identify exercise activity. In addition, study protocols may include mailing these devices to subjects, thus providing the capability to directly measure activity in epidemiologic, telemedicine, and other venues involving distance.