Classification Accuracy of the Wrist-Worn Gravity Estimator of Normal Everyday Activity Accelerometer

• Published in: Medicine and science in sports and exercise 2013-10, Vol.45 (10), p.2012-2019
• Main Authors: WELCH, WHITNEY A., BASSETT, DAVID R., THOMPSON, DIXIE L., FREEDSON, PATTY S., STAUDENMAYER, JOHN W., JOHN, DINESH, STEEVES, JEREMY A., CONGER, SCOTT A., CEASER, TYRONE, HOWE, CHERYL A., SASAKI, JEFFER E., FITZHUGH, EUGENE C.
• Format: Article
• Language: English
• Subjects: Accelerometry - instrumentation; Adult; Biological and medical sciences; Energy Metabolism; Female; Fundamental and applied biological sciences. Psychology; Gravitation; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Male; Medical sciences; Middle Aged; Monitoring, Ambulatory - instrumentation; Motor Activity - physiology; Oxygen Consumption; Physical Exertion - physiology; Space life sciences; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Wrist; Young Adult
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0b013e3182965249

PURPOSEThe purpose of this study was to determine whether the published left-wrist cut points for the triaxial Gravity Estimator of Normal Everyday Activity (GENEA) accelerometer are accurate for predicting intensity categories during structured activity bouts. METHODSA convenience sample of 130 adults wore a GENEA accelerometer on their left wrist while performing 14 different lifestyle activities. During each activity, oxygen consumption was continuously measured using the Oxycon mobile. Statistical analysis used Spearman’s rank correlations to determine the relationship between measured and estimated intensity classifications. Cross tabulations were constructed to show the under- or overestimation of misclassified intensities. One-way χ tests were used to determine whether the intensity classification accuracy for each activity differed from 80%. RESULTSFor all activities, the GENEA accelerometer-based physical activity monitor explained 41.1% of the variance in energy expenditure. The intensity classification accuracy was 69.8% for sedentary activities, 44.9% for light activities, 46.2% for moderate activities, and 77.7% for vigorous activities. The GENEA correctly classified intensity for 52.9% of observations when all activities were examined; this increased to 61.5% with stationary cycling removed. CONCLUSIONSA wrist-worn triaxial accelerometer has modest-intensity classification accuracy across a broad range of activities when using the cut points of Esliger et al. Although the sensitivity and the specificity are less than those reported by Esliger et al., they are generally in the same range as those reported for waist-worn, uniaxial accelerometer cut points.