Introduction: Pregnant women without contraindications for physical activity (PA) should exercise throughout pregnancy. Accelerometers provide an objective measure of PA under free-living conditions. To avoid bias, the recommended miminum number of valid days required to measure PA derived from accelerometry data in adults is currently ≥4. It is unknown if less than the recommended (e.g., 3 d) would prove reliable, thus allowing researchers to preserve sample size. We aimed to examine data reliability of wearing actical accelerometers for 3 days in comparison with the recommendation of ≥4 d in pregnant women.
Methods: Sixteen pregnant women in their 2nd trimester (T2) and 19 in 3rd trimester (T3) had their PA measured by Actical® accelerometers. Participants were instructed to wear the device for seven days. Only women who wore the device for ≥4 d were included. Three days were randomly selected for each participant. Paired comparisons and intraclass correlations (ICCs) were performed for ≥4 d vs. 3 d. Daily averages (min/d) of sedentary time (ST), light- (LPA), moderate- (MPA), vigorous- (VPA), moderate-to-vigorous intensity (MVPA) PA and steps/d were examined.
Results: No differences were found between ≥4 d vs. 3 d for ST, MPA, VPA, and MVPA in T2, with mean differences ranging from -0.29[-1.43;0.84]min (p=0.763) to -1.00[-3.42;1.41]min (p=0.520). LPA (-8.05[-13.47;-2.63]min; p=0.006) and steps/d (-467.47[-837.06;-97.87]steps; p=0.016) were higher in the ≥4 d analysis in T2. No differences were observed between ≥4 d vs. 3 d in T3, with mean differences ranging from -0.13[-2.80;2.53]min (p=0.754) to 4.51[-420.13;429.16]steps (p=0.982). In T2, ICCs varied between 0.918 [0.786;0.968] to 0.976 [0.939;0.991] while ICCs were between 0.866 [0.617;0.953] to 0.950 [0.857-0.983] in T3.
Conclusion: In pregnant women, PA obtained from 3 d of wear were equivalent and presented moderate-to-high agreement with ≥4 d of wear in T2 and T3, with the exception of LPA and steps in T2.
Rachel Colley– Senior Research Analyst, Statistics Canada / Government of Canada
Sara Souza– Graduate Student, University of Ottawa
Shuhiba Mohammad– PhD Student, University of Ottawa
Taniya Nagpal– Post-Doctoral Fellow, University of Ottawa
Kristi Adamo– Supervisor, University of Ottawa