Convergent Validity of a Piezoelectric Pedometer and an Omnidirectional Accelerometer for Measuring Children’s Physical Activity

The aim of this study was to assess the convergent validity of a new piezoelectric pedometer and an omnidirectional accelerometer for assessing children's time spent in moderate to vigorous physical activity (MVPA).A total of 114 children (51 boys, 63 girls) aged 5-11 years wore a sealed NL-1000 piezoelectric pedometer (New Lifestyles Inc, Lee's Summit, MO) and an Actical accelerometer (Mini Mitter, Bend, OR) over one school day. The NL-1000 pedometers were randomized to one of two manual intensity thresholds used to define MVPA (1): Level 3 = 2.9 metabolic equivalent test (MET) and (2) Level 4 = 3.6 MET. Compared with the Actical, the NL-1000 underestimated the time spent in MVPA by 37% and 45% at intensity levels 3 and 4, respectively. In addition, the 95% limits of agreement were wide at both intensity levels (level 3 = -144%, 70%; level 4 = -135%, 45%), indicating a low level of precision.