SPECIAL COMMUNICATIONS Field evaluation of the Computer Science and Applications, Inc. physical activity monitor JOHN R. SIRARD, EDWARD L. MELANSON, LI LI, and PATTY S. FREEDSON Department of Exercise Science, University of Massachusetts, Amherst, MA 01003 ABSTRACT SIRARD, J. R., E. L. MELANSON, L. LI, and P. S. FREEDSON. Field evaluation of the Computer Science and Applications, Inc. physical activity monitor. Med. Sci. Sports Exerc., Vol. 32, No. 3, pp. 695–700, 2000. Purpose: The purpose of this study was to evaluate the Computer Science and Applications, Inc. (CSA) activity monitor to quantify physical activity in free living subjects using an activity diary as the criterion measure. Methods: Subjects also completed a 7-d physical activity recall at the end of the monitoring period. Nine male and 10 female subjects (mean, SD) (25.0, 3.6 yr) wore the CSA monitor for 7 consecutive days. On 3 of those days, subjects completed an activity diary (2 weekdays and 1 weekend day). Total kcal per day (Dkcal tot ) was calculated from the self-reported diary classifications of the subject’s activities. For the 3 days that coincided with the diary, total number of counts accumulated per day (cnt tot ) was obtained from the monitor. Results: The amount of activity per day recorded by the CSA monitor followed the same pattern of change as the activity diary. The cnt tot and Dkcal tot were significantly (P  0.05) correlated on day 1 (r = 0.65), day 2 (r = 0.49), day 3 (r = 0.55), and for the 3 days pooled (r = 0.51). Subjects were classified as low, moderate, or highly active based on tertiles of kcal from the diary and counts from the CSA monitor. The percentage agreement between the CSA and the activity diary was 68.4% (Kappa = 0.53, P  0.01). The number of minutes spent in the various activity categories were compared between instruments using an ANOVA model. The results of these analyses suggest that the CSA overestimated light activity and underestimated vigorous activity compared with the diary. Conclusion: In conclusion, the CSA monitor may be useful in a field situation where total physical activity and patterns of physical activity are the desired outcomes. Key Words: ACTIVITY MONITOR, ACCELEROMETRY, PHYSICAL ACTIVITY, ENERGY EXPENDITURE O ver the past few decades, there has been increased interest and research in the area of physical activity assessment and its relationship to health outcomes. Physical activity has been defined as “any bodily movement produced by skeletal muscles that results in energy expen- diture” (6). The majority of epidemiological studies con- clude that physical inactivity is positively associated with the incidence rates of morbidity and mortality from a num- ber of chronic diseases (10,11,13–15,21). Furthermore, it has been determined that this is a causal relationship (2,15,20). To study this relationship more closely, epidemi- ologists and other researchers have developed a number of measurement tools to assess the quantity of physical activity to establish the levels needed to provide a protective effect from chronic disease. The Centers for Disease Control and Prevention and the American College of Sports Medicine recently adopted a new position stance on the amount of recommended exercise for the adult population of the United States (21). The position of these organizations is that every U.S. adult should accumulate 30 min or more of moderate intensity physical activity on most, preferably all, days of the week (21). This statement provides a generalized quantification for the total amount of physical activity recommended. There has also been increased attention directed to the quantification of physical activity by utilizing mechanical or electronic monitors. These devices provide the necessary objectivity that paper and pencil techniques lack and are not as expensive as the doubly labeled water (DLW) technique. Also, DLW only allows for measurement of total energy expenditure. In certain applications where dose-response relationships are of interest, patterns and intensity levels of physical activity are needed. A recent addition to the activity monitor market, and the subject of this investigation, is the CSA model 7164 (Computer Science and Applications, Inc., Shalimar, FL) accelerometer (8). The CSA model 7164 utilizes the same technology as the previous model (model 5130), but the size of the unit has been reduced making the 0195-9131/00/3203-0695/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE ® Copyright © 2000 by the American College of Sports Medicine Submitted for publication January 1999. Accepted for publication April 1999. 695