Estimating Activity and Sedentary Behavior from an Accelerometer on the Hip or Wrist

Abstract

Previously the National Health and Examination Survey measured physical activity with an accelerometer worn on the hip for seven days, but recently changed the location of the monitor to the wrist. PURPOSE This study compared estimates of physical activity intensity and type with an accelerometer on the hip versus the wrist. METHODS Healthy adults (n=37) wore triaxial accelerometers (Wockets) on the hip and dominant wrist along with a portable metabolic unit to measure energy expenditure during 20 activities. Motion summary counts were created, then receiver operating characteristic (ROC) curves were used to determine sedentary and activity intensity thresholds. Ambulatory activities were separated from other activities using the coefficient of variation (CV) of the counts. Mixed model predictions were used to estimate activity intensity. RESULTS The ROC for determining sedentary behavior had greater sensitivity and specificity (71% and 96%) at the hip than the wrist (53% and 76%), as did the ROC for moderate to vigorous physical activity on the hip (70% and 83%) versus the wrist (30% and 69%). The ROC for the CV associated with ambulation had a larger AUC at the hip compared to the wrist (0.83 and 0.74). The prediction model for activity energy expenditure (AEE) resulted in an average difference of 0.55 (+/− 0.55) METs on the hip and 0.82 (+/− 0.93) METs on the wrist. CONCLUSIONS Methods frequently used for estimating AEE and identifying activity intensity thresholds from an accelerometer on the hip generally do better than similar data from an accelerometer on the wrist. Accurately identifying sedentary behavior from a lack of wrist motion presents significant challenges.

Sedentary Behavior and Cardiovascular Morbidity and Mortality: A Science Advisory From the American Heart Association

“…Participants have traditionally worn accelerometers on a belt around their waist during waking hours and remove them for water-based activities, a methodology and protocol that has been shown to be both valid and reliable. 23,24 Wearing a device on a wrist or ankle can be helpful in quantifying behaviors that have different positions 25,26 and can be less burdensome than using a waist-worn device. The movement detected by accelerometers is converted to electrical signals or "counts" that can be summed over a period of time to quantify total sedentary time (minutes) or patterns of sedentary time (eg, duration of bouts or episodes, breaks in sedentary time).…”

Feasibility of Using a Smartwatch to Intensively Monitor Patients With Chronic Obstructive Pulmonary Disease: Prospective Cohort Study (Preprint)

“…We applied previously established methods to process raw accelerometer sensor data to determine sedentary behavior and physical activity. [16] Initially, raw data was converted to a motion summary count using an area under the curve calculation after removing the effects of gravity, which provided activity counts per minute. Thresholds for sedentary behavior (<50.92 counts/minute) and moderate-vigorous physical activity (>305.36 counts/minute) were used from a validation study of Android devices.…”

The use of cardiac rehabilitation services to aid the recovery of patients with bowel cancer: a pilot randomised controlled trial with embedded feasibility study

“…97 In this study, we suggested to participants that they wear the accelerometer around their waist rather than around their wrist, because wrist-worn accelerometers are not as accurate as hip-worn accelerometers at classifying activity and sedentary behaviour. 196 However, the interviews suggest that wearing the accelerometer in this way was a burden for some participants, especially for those with abdominal wound problems or a stoma. Thus, for the purposes of consistency in measuring the amount of physical activity, all people with CRC should be requested to wear the device on the wrist in future studies.…”