Examining the Agreement Between the activPAL micro4 and ActiGraph GT9X Accelerometers on Daily Movement Behaviors Among Adults With Total Knee Replacement

Objective: The primary purpose was to examine the agreement in sedentary, light, and moderate to vigorous minutes and step counts between the activPAL micro4 and ActiGraph GT9X in adults following total knee replacement. A secondary purpose was to examine the agreement between the activPAL micro4 and ActiGraph GT9X accelerometers at two different time points after surgery (∼1 and 3 months). Methods: Participants in a randomized trial wore ActiGraph GT9X and activPAL micro4 monitors simultaneously for 7 days at ∼1 and 3 months after total knee replacement. The intraclass correlations for time spent in sedentary behavior, light, and moderate to vigorous activity in addition to step counts were estimated to determine consistency between the two monitors. Bland–Altman plot demonstrated the 95% limits of agreement between the monitors at both time points. Results: A total of 480 observations (days) were used from 41 participants (64.9 ± 7 years, 32.4 ± 6.5 kg/m2, 75.6% White, 61% female). The intraclass correlations between the ActiGraph GT9X and activPAL micro4 accelerometers was .839 for sedentary behavior, .853 for light activity, .806 for moderate to vigorous activity, and .937 for steps. The 95% confidence intervals of intraclass correlations between time points indicate a significantly higher agreement between the monitors at 3 months as compared with 1 month. Conclusion: The results suggest that either the ActiGraph GT9X or the activPAL micro4 accelerometers may be used for measuring sedentary, light, and moderate to vigorous minutes and step counts in adults after knee replacement.