TY - JOUR
T1 - Between-monitor differences in step counts are related to body size
T2 - Implications for objective physical activity measurement
AU - Pomeroy, Jeremy
AU - Brage, Søren
AU - Curtis, Jeffrey M.
AU - Swan, Pamela
AU - Knowler, William C.
AU - Franks, Paul W.
PY - 2011
Y1 - 2011
N2 - Background: The quantification of the relationships between walking and health requires that walking is measured accurately. We correlated different measures of step accumulation to body size, overall physical activity level, and glucose regulation. Methods: Participants were 25 men and 25 women American Indians without diabetes (Age: 20-34 years) in Phoenix, Arizona, USA. We assessed steps/day during 7 days of free living, simultaneously with three different monitors (Accusplit-AX120, MTI-ActiGraph, and Dynastream-AMP). We assessed total physical activity during free-living with doubly labeled water combined with resting metabolic rate measured by expired gas indirect calorimetry. Glucose tolerance was determined during an oral glucose tolerance test. Findings: Based on observed counts in the laboratory, the AMP was the most accurate device, followed by the MTI and the AX120, respectively. The estimated energy cost of 1000 steps per day was lower in the AX120 than the MTI or AMP. The correlation between AX120-assessed steps/day and waist circumference was significantly higher than the correlation between AMP steps and waist circumference. The difference in steps per day between the AX120 and both the AMP and the MTI were significantly related to waist circumference. Interpretation: Between-monitor differences in step counts influence the observed relationship between walking and obesity-related traits.
AB - Background: The quantification of the relationships between walking and health requires that walking is measured accurately. We correlated different measures of step accumulation to body size, overall physical activity level, and glucose regulation. Methods: Participants were 25 men and 25 women American Indians without diabetes (Age: 20-34 years) in Phoenix, Arizona, USA. We assessed steps/day during 7 days of free living, simultaneously with three different monitors (Accusplit-AX120, MTI-ActiGraph, and Dynastream-AMP). We assessed total physical activity during free-living with doubly labeled water combined with resting metabolic rate measured by expired gas indirect calorimetry. Glucose tolerance was determined during an oral glucose tolerance test. Findings: Based on observed counts in the laboratory, the AMP was the most accurate device, followed by the MTI and the AX120, respectively. The estimated energy cost of 1000 steps per day was lower in the AX120 than the MTI or AMP. The correlation between AX120-assessed steps/day and waist circumference was significantly higher than the correlation between AMP steps and waist circumference. The difference in steps per day between the AX120 and both the AMP and the MTI were significantly related to waist circumference. Interpretation: Between-monitor differences in step counts influence the observed relationship between walking and obesity-related traits.
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U2 - 10.1371/journal.pone.0018942
DO - 10.1371/journal.pone.0018942
M3 - Article
C2 - 21556140
AN - SCOPUS:79955677453
SN - 1932-6203
VL - 6
JO - PloS one
JF - PloS one
IS - 4
M1 - e18942
ER -