Defining Relative Intensity Physical Activity Bouts From Accelerometer Data

Purpose The purpose of this study is to describe and evaluate a method of defining the intensity of accumulated lifestyle PA bouts from CSA data based upon relative intensity from % heart rate reserve (%HRR)

Methods CSA and %HRR data coflected simultaneously for 12 subjects (7 men, 5 women; 43 total bouts) were analyzed to simulate bouts of exercise and ifestyle activity from self-report Instruments souls were defined from visual inspection of data as groups of 10 consecutive minutes with most minutes having> 1000 CSA cis/min, first and last minutes of the bout> 500 ctslrnin. and ratio of max/mean ets/min <3 5 Mean CSA counts and a criterion of mean %HRR for all bouts were related by a random intercepts regression model from which mean GSA cut-points were derived Bouts were classified as light, moderate, or vigorous based on mean CSA cislmin and mean %HRR Classifications for bouts. days 30 mm moderate PA. and days 20 mm vigorous PA were compared using Kappa statistics and % agreement with the criterion and wh previously published absolute Intensity methods of Freedson, Swartz, and Hendelman.

Results This method compared with mean %HRR had moderate to high correlation (K=0 440 64) in defining bout intensity and in classifying days as moderate and vigorous The published methods with mean %HRR had low to high (K0 12-O.54)correlations Pubtisbed methods with mean %HRR overestimated days and time spent in PA but were closer with vigorous than moderate PA.

Conclusions This analysis method defines PA bouts similar to those asked on PAQs It has good correlation with measured heart rate for classifying lifestyle PA bouts as light, moderate, and vigorous intensity. These data suggest that accumulated bouts of PA of relative Intensity can be measured by CSA accelerometer