Deborah A. Jones

The relationship between pedometer-determined ambulatory activity and body composition variables.

OBJECTIVE: To examine the relationship between pedometer-determined ambulatory activity (steps/day) and body composition variables body mass index (BMI) and percentage body fat).DESIGN: Secondary analysis of a cross-sectional objective activity monitoring study for up to 21 consecutive days.SUBJECTS: A total of 109 apparently healthy adults (eight African American males, 23 African-American females, 33 Caucasian males, 45 Caucasian females), age 44.9±15.8 y, BMI=26.9±5.1 kg/m2.MEASUREMENTS: Pedometer-assessed ambulatory activity (steps/day), height and weight, and percentage body fat by bioelectrical impedance.RESULTS: Analyzed as both a continuous and a categorical variable (determined using 25th and 75th percentiles for distribution for steps/day), ambulatory activity was consistently related to body composition variables. Steps/day was inversely correlated with BMI and percentage body fat (r=−0.30, and r=−0.27, respectively, both P<0.01). The consistency of the relationship was also evident when examined using accepted BMI cut-off points for normal-weight, overweight, and obese categories.CONCLUSIONS: Individuals in this small sample with values greater than approximately 9000 steps/day are more frequently classified as normal weight for height. Individuals with values less than approximately 5000 steps/day are more frequently classified as obese. These findings require further corroborative investigation but provide preliminary cutoff points for identifying individuals at risk who may benefit from appropriate physical activity intervention.

Measuring physical activity with the behavioral risk factor surveillance system

PURPOSE AND METHODS Because regular physical activity reduces the risk of premature death and disability, accurate methods of population-based measurement are important for public health surveillance efforts such as those based on the Behavioral Risk Factor Surveillance System (BRFSS). The present study: 1) briefly reviews and compares currently available methods to measure physical activity using BRFSS data, 2) describes physical activity patterns in the United States using these state-aggregated measures, and 3) provides suggestions on future directions for practitioners and researchers. Using a random-digit dialing, telephone survey, we collected data for noninstitutionalized adults aged 18 yr and older. We analyzed BRFSS data for 1996 from 50 states and the District of Columbia and Puerto Rico (N = 124,085). Based on recent literature and public health priorities, we developed eight different physical activity indices (one vigorous and seven moderate). These varied in their threshold for duration, kcal expenditure, and in frequency and intensity of activity. RESULTS Using different algorithms, the population prevalence of moderate physical activity ranged from about 20% to 38%. Only 20% of adults met the Healthy People 2000 definition for regular, sustained activity (> or =30 min of moderate activity per day for at least 5 d x wk(-1)). CONCLUSIONS Considerable progress is needed if the United States is to reach the current public health goal for regular physical activity. Standardized approaches to analyzing and collecting physical activity data are essential for public health surveillance, policy making, and communication to the public.

Health-related quality of life, BMI and physical activity among US adults (>/=18 years): National Physical Activity and Weight Loss Survey, 2002.

Objective:To examine the association between health-related quality of life (HRQOL) and physical activity (PA).Methods:Cross-sectional data were obtained via a national telephone survey from 9173 respondents (30.9% response rate; 51.4% cooperation rate). Four indicators of HRQOL were measured: self-rated health, physically unhealthy days, mentally unhealthy days and activity limitation days. Prevalence estimates were calculated by body mass index (BMI) category and PA level. Logistic regression evaluated BMI as an effect modifier of the relationship between HRQOL and PA.Results:Inactive adults reported more fair to poor HRQOL than active adults, regardless of BMI category (P<0.001). BMI did not modify the association between PA and any of the four HRQOL indicators.Conclusion:Prevalence of low HRQOL is inversely related to PA participation, and the relationship is not altered by BMI status. Regardless of their weight status, adults should be encouraged to engage in PA.

Limitations on the Use of a Single Screening Question To Measure Sedentary Behavior.

OBJECTIVES This study explored the limitations of identifying sedentary individuals via an existing screening question in a state-based surveillance system. METHODS A national sample (n = 7529) of adults, selected by random-digit dialing between November 1999 and May 2000, responded about participation in leisure-time physical activity. RESULTS Of those who initially reported no leisure-time physical activity (25%), 85% were engaging in at least some activity, and 20% were engaging in enough moderate- or vigorous-intensity activity to meet health-related recommendations. CONCLUSIONS Public health programs that use only 1 screening question to identify sedentary behavior may not be able to target physical activity messages effectively, especially if physical activity is defined to include a broad range of activities beyond sports.