Academic journal article Research Quarterly for Exercise and Sport

Construct Validity Evidence for Single-Response Items to Estimate Physical Activity Levels in Large Sample Studies

Academic journal article Research Quarterly for Exercise and Sport

Construct Validity Evidence for Single-Response Items to Estimate Physical Activity Levels in Large Sample Studies

Article excerpt

Valid measurement of physical activity is important for studying the risks for morbidity and mortality. The purpose of this study was to examine evidence of construct validity of two similar single-response items assessing physical activity via self-report. Both items are based on the stages of change model The sample was 687 participants (men = 504, women = 183) who completed an 8-response (PA8) or 5-response (PA5) single-response item about current level of physical activity. Responses were categorized as meeting or not meeting guidelines for sufficient physical activity to achieve a health benefit. Maximal cardiorespiratory fitness (CRF) and health markers were obtained during a clinical examination. Partial correlation, multivariate analysis of covariance, and logistic regression were used to identify the relations between self-reported physical activity, CRF, and health markers when controlling for gender and age. Single-response items were compared to a detailed measure of physical activity. Single-response items correlated significantly with CRF determined with a maximal exercise test on a treadmill (PA8 = .53; PA5 = .57). Differences in percentage of body fat and cholesterol were in the desired direction, with those self-reporting sufficient physical activity for a health benefit having the lower values. The single-response items demonstrated evidence of construct validity and may provide feasible, cost-effective, and efficient methods to assess physical activity in large-scale studies.

Key words: assessment, feasibility, healthy lifestyle, reliability

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There is clear evidence of a relationship between cardiorespiratory fitness (CRF) and all-cause mortality (Blair et al., 1996, 1989). It is difficult to quantify CRF in large samples. As with CRF, physical activity (PA) has been shown to relate to mortality and morbidity (Sesso, Paffenbarger, & Lee, 2000). Thus, PA has been used in large-scale studies such as the Harvard Alumni Study (Lee, Sesso, & Paffenbarger, 2000) and the Aerobics Center Longitudinal Study (Kohl, Blair, Paffenbarger, Macera, & Kronenfeld, 1988). Nationwide studies, such as the Centers for Disease Control and Prevention's (CDC) Behavioral Risk Factor Surveillance System (BRFSS; Prevalence of physical activity, 2003) and Youth Risk Behavior Surveillance System (YRBSS; Grunbaum et al., 2004), also assess PA. Since the development of the CDC/American College of Sports Medicine (ACSM) PA guidelines (Pate et al., 1995), methods have been developed to assess PA to determine if individuals meet the PA guidelines sufficient for a health benefit. While the PA sufficient for a health benefit has been estimated from a variety of means, one approach assesses whether the individual engages in moderate PA at least 5 days a week for at least 30 min a day or vigorous PA a minimum of 3 days a week for a minimum of 20 min per session (Pate et al., 1995). Regardless of the method used, attempts are made to identify the frequency, intensity, and time of PA.

Caloric expenditure is one way to determine sufficient PA for a health benefit (Lee, Paffenbarger, & Hsieh, 1991), but it is difficult to use in large-scale studies. The most valid field method for obtaining data on daily PA is accelerometry (Freedson & Miller, 2000), but its use in large-scale studies is difficult because of the expense, time, and equipment required.

Various methods have been used to obtain self-reported PA in written forms, and extensive self-report records of typical PA have been developed (Blair et al., 1985). Diaries have been used but are time consuming and burdensome for participants (Arroll, Jackson, & Beaglehole, 1991). The use of other serf-report instruments is widely reported and summarized in Montoye, Kemper, Saris, and Washburn (1996). The questions currently used in the BRFSS were revised in 2001 to better estimate PA sufficient for a health benefit (Prevalence of physical activity, 2003). …

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