A Preliminary Study of One Year of Pedometer Self-Monitoring Catrine Tudor-Locke, Ph.D. Department of Exercise and Wellness Arizona State University David R. Bassett, Jr., Ph.D. Department of Health and Exercise Science The University of Tennessee Ann M. Swartz, Ph.D. and Scott J. Strath, Ph.D. Department of Human Movement Sciences University of Wisconsin-Milwaukee Brian B. Parr, Ph.D. Exercise and Sports Science University of South Carolina Aiken Jared P. Reis, Ph.D. Graduate School of Public Health San Diego State University Katrina D. DuBose, Ph.D. Center for Physical Activity & Weight Management Schiefelbusch Institute for Lifespan Studies University of Kansas Barbara E. Ainsworth, Ph.D. Department of Exercise & Nutritional Sciences San Diego State University ABSTRACT Background: Long-term pedometer monitoring has not been attempted. Purpose: The purpose of this project was to col- lect 365 days of continuous self-monitored pedometer data to explore the natural variability of physical activity. Methods: Twenty-three participants (7 men, 16 women; M age = 38 ± 9.9 years; M body mass index = 27.7 ± 6.2 kg/m 2 ) were recruited by word of mouth at two southern U.S. universities. Participants were asked to wear pedometers at their waist during waking hours and record steps per day and daily behaviors (e.g., sport/exercise, work or not) on a simple calendar. In total, par- ticipants wore pedometers and recorded 8,197 person-days of data (of a possible 8,395 person-days, or 98%) for a mean of 10,090 ± 3,389 steps/day. Missing values were estimated using the Missing Values Analysis EM function in SPSS, Version 11.0.1. Results: A mean of 10,082 ± 3,319 steps/day was com- puted. Using the corrected data, differences in steps/day were significant for season (summer > winter, F = 7.57, p = .001), day of the week (weekday > weekend, F = 3.97, p = .011), type of day (workday vs. nonworkday, F = 9.467, p = .008), and par- ticipation in sport/exercise (day with sport/exercise > day with- out sport/exercise, F = 102.5, p < .0001). Conclusions: These data suggest that surveillance should be conducted in the spring/fall or that an appropriate correction factor should be considered if the intent is to capture values resembling the year-round average. (Ann Behav Med 2004, 28(3):158–162) INTRODUCTION Walking is the most frequently reported type of leisure-time physical activity (1–3). Although walking is also fundamentally important to our daily lives, we have little understanding about how much people walk outside leisure-time contexts. Although most self-report approaches to physical activity assessment in- quire about walking frequency and duration (specifically, brisk walking or walking for exercise), ubiquitous ambulatory activ- ity is more difficult to capture with questionnaires (4,5). Regard- less, walking is likely the most important activity to assess accu- rately, especially in the majority of individuals who do not regularly participate in sport or exercise (6). 158 This study was conducted while Dr. Tudor-Locke, Dr. DuBose, Dr. Ainsworth, and Mr. Reis were at the Prevention Research Center, Ar- nold School of Public Health, University of South Carolina and while Drs. Swartz, Strath, and Parr were at the Department of Health and Ex- ercise Science at The University of Tennessee. We are indebted to Cary Springer (University of Tennessee Statistical Consulting Services) for conducting the statistical analyses and to Pat- rick Schneider for assisting with data entry and processing. Finally, we thank our participants for their daily contributions to this study. Reprint Address: C. Tudor-Locke, Ph.D., Department of Exercise and Wellness, Arizona State University, 7001 East Williams Field Road, Mesa, AZ 85212. E-mail: Tudor-Locke@asu.edu © 2004 by The Society of Behavioral Medicine.