Abstract
Objectives
To derive accelerometer count thresholds for classifying time spent in sedentary,
light intensity, and moderate-to-vigorous physical activity (MVPA) in manual wheelchair
users (MWUs) with spinal cord injury (SCI).
Design
Participants completed 18 activities of daily living and exercises for 10 minutes
each with a 3-minute break between activities while wearing a COSMED K4b2 portable
metabolic cart and an ActiGraph activity monitor on the dominant wrist. A linear regression
was computed between the wrist acceleration vector magnitude and SCI metabolic equivalent
of task (MET) for 80% of the participants to obtain thresholds for classifying different
activity intensities, and the obtained thresholds were tested for accuracy on the
remaining 20% of participants. This cross-validation process was iterated for 1000
times to evaluate the stability of the thresholds on data corresponding to different
proportions of sedentary, light intensity, and MVPA. MET values of 1.5 or lower were
classified as sedentary behavior, MET values between 1.5 and 3 were classified as
light intensity, and MET values of 3 or higher were classified as MVPA. The final
thresholds were then validated on an out-of-sample independent dataset.
Participants
MWUs (N=17) with SCI in the out-of-sample validation data set.
Interventions
Not applicable.
Setting
Research lab, community
Main Outcome Measures
Accelerometer thresholds to classify sedentary, light intensity, and MVPA were obtained
and their accuracy tested using cross-validation and an out-of-sample dataset.
Results
The threshold between sedentary and light intensity was 2057 counts-per-minute, and
the threshold between light intensity and MVPA was 11,551 counts per minute. Based
on the out-of-sample validation, the obtained thresholds had an overall accuracy of
85.6%, with a sensitivity and specificity of 95.3% and 97.4% for sedentary behavior,
87.8% and 84.5% for light intensity, 68.5% and 96.3% for MVPA, respectively.
Conclusion
Accelerometer-based thresholds can be used to accurately identify sedentary behavior.
However, thresholds may not provide accurate estimations of MVPA throughout the day
when participants engage in more resistance-based activities.
Keywords
List of abbreviations:
ADL (activities of daily living), CI (confidence interval), CPM (counts per minute), HERL (Human Engineering Research Lab), ICC (intraclass correlation coefficient), LOA (limits of agreement), MCCV (Monte Carlo cross-validation), MET (metabolic equivalent of task), MVPA (moderate-to-vigorous physical activity), MWU (manual wheelchair user), PA (physical activity), ROC-AUC (area under the receiver operating characteristic curve), SCI (spinal cord injury), VM (vector magnitude), V̇o2 (oxygen consumption per unit time)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: June 02, 2020
Footnotes
Supported by the VA Rehabilitation Research & Development, Merit Review (grant no. 1101RX000971-01A), conducted at the Human Engineering Research Laboratories (Pittsburgh, PA) and the James J. Peters VA Medical Center (Bronx, NY). This study also used data from another study funded by National Institute of Disability, Independent Living and Rehabilitation Research (NIDILRR), Rehabilitation Engineering Research Center on Recreational Technologies Benefiting Individuals with Disabilities (#H133E120005), conducted at the Human Engineering Research Laboratories (Pittsburgh, PA) and the Lakeshore Foundation (Birmingham, AL). The contents do not represent the views of the Department of Veterans Affairs or the United States Government.
Disclosures: none.
Identification
Copyright
© 2020 Published by Elsevier Inc. on behalf of the American Congress of Rehabilitation Medicine
