Academic journal article Research Quarterly for Exercise and Sport

Using Momentary Time Sampling to Estimate Minutes of Physical Activity in Physical Education: Validation of Scores for the System for Observing Fitness Instruction Time

Academic journal article Research Quarterly for Exercise and Sport

Using Momentary Time Sampling to Estimate Minutes of Physical Activity in Physical Education: Validation of Scores for the System for Observing Fitness Instruction Time

Article excerpt

A number of major organizations and influential individuals involved in promoting physical activity have emphasized the importance of valid and reliable physical activity measures (Pate et al., 1995; U.S. Department of Health and Human Services, 2000). Given some of the problems with self-reported activity, many recommendations for monitoring physical activity have included objective measurement devices and direct observation (Dishman, 1994; Dishman & Buckworth, 1996; Freedson & Miller, 2000; Lamonte & Ainsworth, 2001; Sallis & Saelens, 2000; Welk, Corbin, & Dale, 2000).

The System for Observing Fitness Instruction Time (SOFIT) is a direct observation system specifically developed for use during physical education (PE; McKenzie, 1991; McKenzie, Sallis, & Nader, 1991). Although the SOFIT has been used extensively to evaluate physical activity outcomes for large community-based studies of children's health, such as the Child and Adolescent Trial for Cardiovascular Health (CATCH; Luepker et al., 1996) and Sports, Play, and Active Recreation for Kids (SPARK; Sallis et al., 2003), only four published peer-reviewed studies have validated its intensity categories (McKenzie et al., 1991; McKenzie, Sallis, & Armstrong, 1994; Pope, Coleman, Gonzalez, Barron, & Heath, 2002; Rowe, Schuldheisz, & van der Mars, 1997). Of these studies, only two were done during actual PE classes in which use of the SOFIT was likely to occur (McKenzie, Sallis et al., 1994; Pope et al., 2002), and one was published in abstract form only (McKenzie, Sallis et al., 1994).

The data collected with the SOFIT are most commonly expressed as a percentage of lesson time during PE devoted to a specific physical activity intensity (Luepker et al., 1996; McKenzie, Strickmiller, & Stone, 1994; Heath & Coleman, 2002). It is not a direct measure of the time spent in an activity but an estimate based on a behavioral observation every 20 s throughout the PE period. Because of this estimation method, the SOFIT may not accurately reflect the actual time children spend in a particular intensity category, such as moderate-to-vigorous physical activity (MVPA). All recommendations for physical activity for adults and children have included intensity, frequency, and duration (Council on Physical Education for Children, 2004; Pate et al., 1995; U.S. Department of Health and Human Services, 1996). To expand the use of the SOFIT as an indicator of children's activity in relation to public health guidelines, its scores must be established as valid indicators of both the intensity and the time spent in various types of activity.

The purpose of this study was to validate the estimates of time spent in various physical activity intensities obtained with the paper and pencil versions of the five(McKenzie et al., 1991) and six-category (Pope et al., 2002) SOFIT scales during actual PE classes, using a computerized system of recording and timekeeping. This type of validation has traditionally been identified as concurrent validity. We hypothesized that there would be no difference between SOFIT paper and pencil estimates of time spent in various physical activity intensities and the actual time recorded in each activity intensity category.

Method

Participants

One hundred forty-eight third-, fourth-, and fifth-grade boys (n = 74) and girls (n = 74) were observed during PE classes at five elementary schools in Cache County, UT, and two schools in El Paso, TX, in fall 2000, spring 2001, and fall 2001. A total of 12 third-, 12 fourth-, and 13 fifth-grade classes were observed (N = 37 classes). Consent was obtained from the school districts, principals, and PE instructors to observe classes as they were conducted. Consent was also obtained from the parents to allow their children to participate, if selected. During this process, individual children were not identified, and data were summed and presented as a class. …

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