Validity of accelerometry for measurement of activity in people with brain injury

Tweedy, Sean M. & Trost, Stewart G. (2005) Validity of accelerometry for measurement of activity in people with brain injury. Medicine and Science in Sports and Exercise, 37(9), pp. 1474-1480.

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To evaluate the validity of a uniaxial accelerometer (MTI Actigraph) for measuring physical activity in people with acquired brain injury (ABI) using portable indirect calorimetry (Cosmed K4b(2)) as a criterion measure.


Fourteen people with ABI and related gait pattern impairment (age 32 +/- 8 yr) wore an MTI Actigraph that measured activity (counts(.)min-(1)) and a Cosmed K4b(2) that measured oxygen consumption (mL(.)kg(-1.)min(-1)) during four activities: quiet sitting (QS) and comfortable paced (CP), brisk paced (BP), and fast paced (FP) walking. MET levels were predicted from Actigraph counts using a published equation and compared with Cosmed measures. Predicted METs for each of the 56 activity bouts (14 participants X 4 bouts) were classified (light, moderate, vigorous, or very vigorous intensity) and compared with Cosmed-based classifications.


Repeated-measures ANOVA indicated that walking condition intensities were significantly different (P < 0.05) and the Actigraph detected the differences. Overall correlation between measured and predicted METs was positive, moderate, and significant (r = 0.74). Mean predicted METs were not significantly different from measured for CP and BP, but for FP walking, predicted METs were significantly less than measured (P < 0.05). The Actigraph correctly classified intensity for 76.8% of all activity bouts and 91.5% of light- and moderate-intensity bouts.


Actigraph counts provide a valid index of activity across the intensities investigated in this study. For light to moderate activity, Actigraph-based estimates of METs are acceptable for group-level analysis and are a valid means of classifying activity intensity. The Actigraph significantly underestimated higher intensity activity, although, in practice, this limitation will have minimal impact on activity measurement of most community-dwelling people with ABI.

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20 citations in Web of Science®

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ID Code: 71977
Item Type: Journal Article
Refereed: Yes
Additional Information: ISI Document Delivery No.: 967FY Times Cited: 13 Cited Reference Count: 23 Tweedy, SM Trost, SG Lippincott williams & wilkins Philadelphia; <Go to ISI>://WOS:000232078100004
Keywords: activity monitors, health promotion, physical activity, rehabilitation, stroke, traumatic brain injury, csa activity monitor, computer-science, validation, inc.
DOI: 10.1249/
ISSN: 0195-9131
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Deposited On: 22 May 2014 01:44
Last Modified: 22 May 2014 01:44

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