Academic journal article Research Quarterly for Exercise and Sport

Detecting Bouts of Physical Activity in a Field Setting

Academic journal article Research Quarterly for Exercise and Sport

Detecting Bouts of Physical Activity in a Field Setting

Article excerpt

Current physical activity recommendations (Pate et al., 1995; National Institutes of Health, 1995) state that health benefits can result by "accumulating 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the week." Thus, physical activity accumulated in short bouts (i.e., as short as 810-min in duration) may also confer health benefits similar to those achieved with continuous physical activity. Accurate measurement of intermittent physical activity (i.e., physical activity accumulated in short bouts) is essential to determine if health benefits can be gained by accumulated physical activity and if national physical activity recommendations are being achieved.

Many methods can be used to measure physical activity (Ainsworth, Montoye, & Leon, 1994). Objective monitoring instruments, such as accelerometers, offer investigators a viable alternative to other instruments, because accelerometers can measure and record intermittent physical activity over extended periods, with little participant burden. Monitoring instruments, such as the TRITRAC[R] and CSA[R] accelerometers, can detect short bouts of physical activity, because they continuously record data in brief intervals (e.g., 30 s) for periods up to 2 weeks. While using accelerometers may be an accurate method to detect bouts of physical activity, investigators have historically used accelerometers to estimate total energy expenditure (Ballor, Burke, Knudson, Olson, & Montoye, 1989; Balogun, Martin, & Clendenin, 1989; Bouten, Westerterp, Verduin, & Janssen, 1994; Bray, Wong, Morrow, Butte, & Pivarnik, 1994; Freedson, Melanson, & Sirard, 1998; Gretebeck & Montoye, 1992; Haymes & Byrnes, 1993; Matthews & Freedson, 1995, Melanson & Freedson, 1995; Nichols, Patterson, & Early, 1992; Pambianco, Wing, & Robertson, 1990; Servais & Montoye, 1984). Few investigators have compared or determined the reliability or validity of accelerometers in detecting bouts of physical activity (i.e., less than 30 min).

Several investigators have reported the reproducibility and interinstrument reliability of accelerometers. Reproducibility is high, with correlation coefficients ranging from .91 to .98 (Kochersberger, McConnell, Kuchibhatla, & Pieper, 1996; Meijer, Westerterp, Verhoeven, Koper, & ten Hoor, 1991; Nichols et al., 1992; Pambianco et al., 1990). Investigators have also shown accelerometers to have high interinstrument reliability, both in the laboratory and in the field, when walking or running is the main activity (r = .87 to .98; Pambianco et al., 1990; Sallis, Buono, Roby, Carlson, & Nelson, 1990). These findings suggest that accelerometers have high interinstrument agreement and reliability; however, researchers have not studied the degree to which accelerometers can reliably assess bouts of physical activity.

Several studies have attempted to validate accelerometers using maximal oxygen uptake (Ballor et al., 1989; Gretebeck & Montoye, 1992; Melanson & Freedson, 1995; Melanson & Freedson, 1996; Pambianco et al., 1990), total energy expenditure (Ballor et al., 1989, Melanson & Freedson, 1996; Pambianco et al., 1990), heart rate telemetry (Coleman, Saelens, Wiedrich-Smith, Finn, & Epstein, 1997; Gretebeck & Montoye, 1992; Janz, 1994; Sallis et al., 1990; Welk & Corbin, 1995), visual observation (Klesges, Klesges, Swenson, & Pheley, 1985), physical activity diaries (Coleman et al., 1997; Freedson & Evenson, 1991; Haymes & Byrnes, 1993, Richardson, Leon, Jacobs, Ainsworth, & Serfass, 1995; Williams, Klesges, Hanson, & Eck, 1989), and energy intake as validation criteria (Meijer et al., 1991). Further, investigators have used motion sensors (Taylor, Coffey, Iaffaldano, Casey, & Haskell, 1984) and accelerometers (Kochersberger et al., 1996; Haymes & Byrnes, 1993) to categorize individuals' physical activity levels. …

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