Accelerometers are frequently used to measure physical activity (PA) in children, which is important for overall health and development. Lack of uniformity in data processing methods, such as the metric used to summarize accelerometer data, limits comparability between studies. The objective was to determine the convergent validity of five accelerometer metrics for characterizing the intensity and temporal patterns of first and second graders' (n=88) recess PA. At a 5-s epoch level, Pearson's correlations between various metrics ranged from 0.69 to 0.98. When each epoch was classified into one of four activity levels based on quartiles, agreement between metrics as indicated by weighted kappa ranged from 0.81 to 0.96. When collapsed to time spent in each activity level, metrics were most often statistically equivalent for estimating time spent in quartile 3 or 4. Children were ranked from least to most active, and agreement between metrics was strong with Spearman's correlation coefficients of over r=0.86. Temporal patterns were characterized using five fragmentation indices calculated using each of the five metrics. Pearson's correlations between metrics ranged from r=0.53 to 0.99, with the strongest associations for number of high activity bouts. Most fragmentation indices were not statistically equivalent between metrics. While metrics captured similar trends in activity intensity and temporal patterns, caution is warranted when making comparisons of point estimates derived from different metrics. However, all metrics were able to similarly capture higher intensity activity (i.e., quartile 3 or 4), the most common outcome of interest in intervention studies.
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