Validity of proximity sensor-based wear-time detection using the ActiGraph GT9X

ABSTRACT

Our study investigated the performance of proximity sensor-based wear-time detection using the GT9X under laboratory and free-living settings. Fifty-two volunteers (23.2 ± 3.8 y; 23.2 ± 3.7 kg/m²) participated in either a laboratory or free-living protocol. Lab participants wore and removed a wrist-worn GT9X on 3–5 occasions during a 3-hour directly observed activity protocol. The 2-day free-living protocol used an independent temperature sensor and self-report as the reference to determine if wrist and hip-worn GT9X accurately determined wear (i.e., sensitivity) and non-wear (i.e., specificity). Free-living estimates of wear/non-wear were also compared to Troiano 2007 and Choi 2012 wear/non-wear algorithms. In lab, sensitivity and specificity of the wrist-worn GT9X in detecting total minutes of wear-on and off was 93% and 49%, respectively. The GT9X detected wear-off more often than wear-on, but with a greater margin of error (4.8 ± 11.6 vs. 1.4 ± 1.4 min). In the free-living protocol, wrist and hip-worn GT9X’s yielded sensitivity and specificity of 72 and 90% and 84 and 92%, respectively. GT9X estimations had inferior sensitivity but superior specificity to Troiano 2007 and Choi 2012 algorithms. Due to inaccuracies, it may not be advisable to singularly use the proximity-sensor-based wear-time detection method to detect wear-time.

KEYWORDS:

• Wear-time
• physical activity assessment
• accelerometry
• multi-sensor

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by funding from the National Cancer Institute of the National Institutes of Health under contract award number HHSN261201300082C. Enabling technology used in this work was made possible by funding from the U.S. Department of Health and Human Services, National Institutes of Health, National Heart, Lung, and Blood Institute under award number UO1HL091737.