Comparison of Two Accelerometers for Measuring Physical Education Physical Activity in 8th Grade Youth

Abstract

The New Lifestyles NL-1000 (NL; New Lifestyles Inc., Lee's Summit, Missouri) offers promise for use in objective physical activity (PA) assessment applications such as surveillance, self-monitoring, and program evaluation. The NL is a low cost ($48) single-axis accelerometer that outputs daily accumulated time in moderate-to-vigorous physical activity (MVPA) and steps on a simple display screen (i.e., similar to a pedometer). PURPOSE: This study compared MVPA time outputs and classification agreement for quantifying the percent of Physical Education lesson time (%_PELT) in MVPA between the NL and the more commonly used ActiGraph (AG; Actigraph, LLC, Fort Walton Beach, Florida) accelerometers in 8th grade youth during participation in Physical Education (PE). METHODS: Participants (N=169, females=81, males=88) wore both accelerometers attached to an elastic waist belt during a gender segregated 35 minute PE class. NL monitor displays were reset before each class and time spent in MVPA as displayed was recorded by researchers immediately following each class. AG data were downloaded and exported into Excel for processing. AG time in MVPA was determined based on thresholds validated in youth by Treuth et al (2004). Means, standard deviations, and difference values (i.e., AG - NL) were calculated for minutes in MVPA by accelerometer. A paired t-test was used to compare MVPA outputs. Classification agreement (kappa) was calculated for NL and AG determinations of participants achieving 30%, 40%, and 50%_PELT in MVPA. RESULTS: The NL and AG monitors respectively detected an average of 10.2±4.9 and 10.4±6.5 minutes of MVPA during PE. This group level comparison was non-significant (p=0.37). Individual differences between NL and MTI MVPA outputs ranged from −9.6 to 6.8 minutes with a mean difference of 0.2±2.9 minutes. Classification agreement between NL and AG determined participants achieving 30%, 40%, and 50%_PELT in MVPA respectively were 87.0% (kappa=.74), 85.2% (kappa=.65), and 89.3% (kappa=.46). CONCLUSION: The NL is a low cost, user friendly monitor that could be used to assess the %_PELT spent in MVPA during PE. The NL provided similar outputs of MVPA in a combined sample of 8th grade males and females. Additional research is required to extend current findings within PE to longer duration, free-living periods.