Validation of a new self-report instrument for measuring physical activity

Purpose: Development and validation of a physical activity scale for measuring physical activity in 24 h of sports, work, and leisure time on an average weekday. Methods: For development of the physical activity scale, 2500 randomly selected Danish men and women between the age of 20 and 60 were contacted by mail and asked to select frequent and relevant physical activities from a number of activities of known MET intensity. The activities were included in the physical activity scale, organized in nine different MET levels ranging from sleep/rest (0.9 METs) to high-intensity physical activities (>6 METs). Face validity of the physical activity scale was explored through interviews with 10 volunteer men and women. Concurrent validity was assessed against 4 d of accelerometry (CSA 7164) and physical activity diary in 40 volunteer men and women between 20 and 60 yr of age. Results: The correlation between the activity scale and the diary was high (r = 0.74, P = 0.000), whereas correlation between the activity scale and accelerometer measurements was poor (r = 0.20, NS). The physical activity scale MET-time was systematically higher than average MET-time estimated from the diary, and the difference increased with increasing total MET-time. Conclusion: The physical activity scale appears to be a simple and valid alternative to measuring physical activity by diary in adult sedentary to moderately active Danes. The scale encompasses work, leisure time, and sports activity in one measure; it is easy to administer, and it provides detailed information on different activity levels as well as a single measure of the total amount of physical activity on an average weekday.