Cross-validation of Waist-Worn GENEA Accelerometer Cut-Points

WELCH, WHITNEY A.1; BASSETT, DAVID R.1; FREEDSON, PATTY S.2; JOHN, DINESH3; STEEVES, JEREMY A.1; CONGER, SCOTT A.1; CEASER, TYRONE G.1; HOWE, CHERYL A.2; SASAKI, JEFFER E.2

Medicine & Science in Sports & Exercise: September 2014 - Volume 46 - Issue 9 - p 1825–1830
doi: 10.1249/MSS.0000000000000283
Applied Sciences

Purpose: The purpose of this study was to determine the classification accuracy of the waist gravity estimator of normal everyday activity (GENEA) cut-points developed by Esliger et al. for predicting intensity categories across a range of lifestyle activities.

Methods: Each participant performed one of two routines, consisting of seven lifestyle activities (home/office, ambulatory, and sport). The GENEA was worn on the right waist, and oxygen uptake was continuously measured using the Oxycon mobile. A one-way chi-squared test was used to determine the classification accuracy of the GENEA cut-points. Cross-tabulation tables provided information on under- and overestimations, and sensitivity and specificity analyses of the waist cut-points were also performed.

Results: Spearman rank order correlation for the GENEA gravity-subtracted signal vector magnitude and Oxycon mobile MET values was 0.73. For all activities combined, the GENEA accurately predicted intensity classification 55.3% of the time, and it increased to 58.3% when stationary cycling was removed from the analysis. The sensitivity of the cut-points for the four intensity categories ranged from 0.244 to 0.958, and the specificity ranged from 0.576 to 0.943.

Conclusion: In this cross-validation study, the proposed GENEA cut-points had a low overall accuracy rate for classifying intensity (55.3%) when engaging in 14 different lifestyle activities.

1Department of Kinesiology, Recreation, and Sport Studies, University of Tennessee, Knoxville, TN; 2Department of Kinesiology, University of Massachusetts, Amherst, MA; and 3Department of Health Sciences, Northeastern University, Boston, MA

Address for correspondence: Whitney A. Welch, M.S., Department of Kinesiology, University of Wisconsin–Milwaukee, Enderis Hall Room 416, P.O. Box 413, Milwaukee, WI 53201; E-mail: wawelch@uwm.edu.

Submitted for publication August 2013.

Accepted for publication January 2014.

© 2014 American College of Sports Medicine