Equating accelerometer estimates among youth: The Rosetta Stone 2.
OBJECTIVE
Different accelerometer cutpoints used by different researchers often yields vastly different estimates of moderate-to-vigorous intensity physical activity (MVPA). This is recognized as cutpoint non-equivalence (CNE), which reduces the ability to accurately compare youth MVPA across studies. The objective of this research is to develop a cutpoint conversion system that standardizes minutes of MVPA for six different sets of published cutpoints.


METHODS
Secondary data analysis.


METHODS
Data from the International Children's Accelerometer Database (ICAD; Spring 2014) consisting of 43,112 Actigraph accelerometer data files from 21 worldwide studies (children 3-18 years, 61.5% female) were used to develop prediction equations for six sets of published cutpoints. Linear and non-linear modeling, using a leave one out cross-validation technique, was employed to develop equations to convert MVPA from one set of cutpoints into another. Bland Altman plots illustrate the agreement between actual MVPA and predicted MVPA values.


RESULTS
Across the total sample, mean MVPA ranged from 29.7MVPAmind(-1) (Puyau) to 126.1MVPAmind(-1) (Freedson 3 METs). Across conversion equations, median absolute percent error was 12.6% (range: 1.3 to 30.1) and the proportion of variance explained ranged from 66.7% to 99.8%. Mean difference for the best performing prediction equation (VC from EV) was -0.110mind(-1) (limits of agreement (LOA), -2.623 to 2.402). The mean difference for the worst performing prediction equation (FR3 from PY) was 34.76mind(-1) (LOA, -60.392 to 129.910).


CONCLUSIONS
For six different sets of published cutpoints, the use of this equating system can assist individuals attempting to synthesize the growing body of literature on Actigraph, accelerometry-derived MVPA.
University of South Carolina, Department of Exercise Science, USA. Electronic address: brazendk@email.sc.edu.
Keith
K
Brazendale
University of South Carolina, Department of Exercise Science, USA.
Michael W
MW
Beets
University of South Carolina, Department of Exercise Science, USA.
Daniel B
DB
Bornstein
University of South Carolina, Department of Health Promotion, Education, and Behavior, USA.
Justin B
JB
Moore
University of South Carolina, Department of Exercise Science, USA.
Russell R
RR
Pate
University of South Carolina, Department of Exercise Science, USA.
Robert G
RG
Weaver
University of South Carolina, Department of Exercise Science, USA.
Ryan S
RS
Falck
University of South Carolina, Department of Exercise Science, USA.
Jessica L
JL
Chandler
University of Southern Denmark, Department of Sport Science and Clinical Biomechanics, Denmark; Norwegian School of Sport Science, Norway.
Lars B
LB
Andersen
Norwegian School of Sport Science, Norway.
Sigmund A
SA
Anderssen
Ghent University, Department of Movement and Sports Sciences, Belgium.
Greet
G
Cardon
University of Bristol, Centre for Exercise, Nutrition and Health Sciences/School of Social and Community Medicine, UK.
Ashley
A
Cooper
University of Canberra, Centre for Research and Action in Public Health, Australia.
Rachel
R
Davey
University of Southern Denmark, Department of Sport Science and Clinical Biomechanics, Denmark.
Karsten
K
Froberg
Federal University of Pelotas, Brazil.
Pedro C
PC
Hallal
University of Iowa, Department of Health and Human Physiology, USA.
Kathleen F
KF
Janz
University of Bristol, Centre for Exercise, Nutrition and Health Sciences/School of Social and Community Medicine, UK.
Katarzyna
K
Kordas
University of Zürich, Epidemiology, Biostatistics and Public Health Institute, Switzerland.
Susi
S
Kriemler
University of Lausanne, Service of Endocrinology, Diabetes and Metabolism, Switzerland.
Jardena J
JJ
Puder
University of Glasgow, Division of Developmental Medicine, UK.
John J
JJ
Reilly
Deakin University, School of Exercise and Nutrition Sciences/Centre for Physical Activity and Nutrition Research, Australia.
Jo
J
Salmon
Technical University of Lisbon, Faculty of Human Movement, Portugal.
Luis B
LB
Sardinha
University of Glasgow, Division of Developmental Medicine, UK.
Anna
A
Timperio
University of Cambridge, MRC Epidemiology Unit, UK.
Esther M F
EMF
van Sluijs
D061725:Accelerometry / Q000592:standards*; D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D012016:Reference Values
Children; Cutpoints; MVPA; Measurement; Policy; Public health