Can accelerometry be used to discriminate levels of activity?

The aims of this study were to investigate the associations between an activity logbook and the RT3 accelerometer and to assess whether the RT3 can discriminate activity levels in healthy adults. Ten participants completed two trials wearing an RT3 accelerometer over a 4-6 h period and completed a detailed activity log. Results showed a poor correlation between the RT3 in moderate activities (r = 0.22) in comparison to low (r = 0.52) and hard (r = 0.70) from the logbook. A significant difference was found in average RT3 vector magnitude (VM) counts/min in each activity level (p < 0.0001). Discriminant analysis demonstrated that an RT3VM counts/min value of approximately 500 was found to have high sensitivity (88%), and specificity (88%) for discriminating between low and moderate activity levels from the logbook. This study found that accelerometry has the potential to discriminate activity levels in free living. This study is the first to investigate whether tri-axial accelerometry can discriminate different levels of free-living activity recorded in an activity logbook. The RT3 accelerometer can discriminate between low and moderate physical activities and offers a methodology that may be applicable to future research in occupational settings.