Protocol for Objective Measurement of Infants’ Physical Activity using Accelerometry

Purpose To evaluate methods for infants' physical activity measurement based on accelerometry, including the minimum number of measurement days and placement of a wrist or ankle device. We also evaluated the acceptability of the device among infants and mothers. Methods A cross-sectional mixed-methods study was conducted on a convenience sample of 90 infants. Physical activity was measured using the Actigraph GT3X+ accelerometer placed on the wrist and/or ankle for seven consecutive days (worn for 24 hours), and a qualitative interview was performed to verify acceptability. The intraclass correlation coefficient method and the Bland and Altman's dispersion diagram were used to verify the minimum number of measurement days. All analyses were stratified by walking status. Results The mean age was 12.9 months (SD 1.70); the mean acceleration varied between 25.8 mg (95% CI 14.3-52.7) to 27.3 mg (95% CI 17.9-44.5) using the wrist placement; and between 24.9 mg (95% CI 10.6-48.4) to 26.2 mg (95% CI 11.7-65.6) using the ankle placement. The ICC results showed a lower acceleration variability between days among infants incapable of walking; they achieved the ICC=0.80 with one day of measurement in both placements. Among those capable of walking, the minimum number of days to achieve ICC=0.80 were two days measured at the wrist (0.85; 95% CI 0.71-0.93) and three days measured at the ankle (0.92; 95% CI 0.84-0.96). The qualitative results pointed to the wrist placement as the preferred placement among the overall sample. Conclusion Two and three measurement days with the accelerometer placed on the wrist and ankle, respectively, seemed to adequately represent a week of measurement. The accelerometer placed on the wrist had better acceptance by the infants and mothers. This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Corresponding author: Luiza Isnardi Cardoso Ricardo, Marechal Deodoro, 1160 (3rd floor) Pelotas, RS - Brazil, CEP: 96020-220 – phone/fax: +55 (53) 3284 - 1300. E-mail: luizaicricardo@gmail.com Ms. Luiza Ricardo and Ms. Rafaela Martins are funded by the CAPES PhD scholarship, and Ms. Andrea Wendt is funded by a CNPq PhD scholarship. This work was supported by the Wellcome Trust (Grant number: 095582/Z/11/Z). The results of the present study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation; and do not constitute endorsement by the authors or the ACSM. Accepted for Publication: 23 November 2017 © 2017 American College of Sports Medicine

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