Accuracy of Intensity and Inclinometer Output of Three Activity Monitors for Identification of Sedentary Behavior and Light-Intensity Activity

Lucas J Carr,Matthew T Mahar

doi:10.1155/2012/460271

Abstract

Purpose. To examine the accuracy of intensity and inclinometer output of three physical activity monitors during various sedentary and light-intensity activities. Methods. Thirty-six participants wore three physical activity monitors (ActiGraph GT1M, ActiGraph GT3X+, and StepWatch) while completing sedentary (lying, sitting watching television, sitting using computer, and standing still) light (walking 1.0 mph, pedaling 7.0 mph, pedaling 15.0 mph) intensity activities under controlled settings. Accuracy for correctly categorizing intensity was assessed for each monitor and threshold. Accuracy of the GT3X+ inclinometer function (GT3X+Incl) for correctly identifying anatomical position was also assessed. Percentage agreement between direct observation and the monitor recorded time spent in sedentary behavior and light intensity was examined. Results. All monitors using all thresholds accurately identified over 80% of sedentary behaviors and 60% of light-intensity walking time based on intensity output. The StepWatch was the most accurate in detecting pedaling time but unable to detect pedal workload. The GT3X+Incl accurately identified anatomical position during 70% of all activities but demonstrated limitations in discriminating between activities of differing intensity. Conclusions. Our findings suggest that all three monitors accurately measure most sedentary and light-intensity activities although choice of monitors should be based on study-specific needs.

Highlights

Physical inactivity is a leading preventable cause of allcause mortality [1] and has been identified as one of the most important public health problems of the 21st century [2]
Physical inactivity has traditionally been considered the absence of physical activity at the moderate-to-vigorous intensity level which mistakenly combines the large portion of time individuals spend engaged in sedentary behaviors and light-intensity activities
When examining the minutes correctly identified as sedentary, all three physical activity monitors accurately identified over 80% of all sedentary activities as sedentary using multiple thresholds for sedentary behavior

Summary

Introduction

Physical inactivity is a leading preventable cause of allcause mortality [1] and has been identified as one of the most important public health problems of the 21st century [2]. Physical inactivity has traditionally been considered the absence of physical activity at the moderate-to-vigorous intensity level which mistakenly combines the large portion of time individuals spend engaged in sedentary behaviors and light-intensity activities. Sedentary behavior is defined as those activities that do not increase energy expenditure substantially above the resting level (i.e., 1.0–1.5 metabolic equivalent units (METs) [3] and includes activities such as sleeping (0.95 METs), lying down (1.0–1.3 METs), sitting watching television (1.3 METs), sitting at a computer doing light office work (1.5 METs), and standing still quietly (1.3 METs) [4]. In a cross-sectional study of 1,958 older men and women residing in Australia, both self-reported sitting time and television viewing time were associated with increased risk for metabolic syndrome [5]. Objectively assessed sedentary time (via physical activity monitors) has been

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Discussion

Conclusion