Harmonizing Monitor- and Report-Based Estimates of Physical Activity Through Calibration

A major challenge in public health research on physical activity is in reconciling the commonly observed differences between estimates provided by monitor-based methods and report-based methods. Calibration methods are widely used in measurement research to rescale or convert an estimate so that it matches a more robust criterion value. Accelerometry-based activity monitors are routinely calibrated against more robust estimates of indirect calorimetry, but surprisingly little research is done to calibrate report-based estimates. The purpose of the paper was to document the utility of calibration methods for harmonizing estimates from report-based measures to correspond with data from monitor-based methods. While there are also limitations associated with monitor-based methods, this procedure provides a systematic way to promote harmonization of estimates obtained from these different methods. This enables the more feasible report-based measures to provide more accurate group-level estimates of physical activity for different research applications.