Validity Of Accelerometry In Ambulatory Children And Young Adults With Cerebral Palsy

Abstract

PURPOSE: This study aimed to validate five published ActiGraph (AG) cut-off points for the measurements of physical activity (PA) and sedentary time (ST) in ambulatory children and young adults with cerebral palsy (CP). Additionally, four energy expenditure (EE) prediction equations based on AG counts and activPAL (AP) steps were examined in this population, using oxygen uptake (VO2) as the criterion. METHODS: Four male and six female participants with CP (GMFCS levels I-III, ages 9-21 years) completed seven activities while simultaneously wearing an AG, AP monitor and indirect calorimetry unit. VO2 was measured on a breath-by-breath basis using the indirect calorimetry and was converted into EE using metabolic equivalents. AG counts were classified as sedentary, light PA (LPA) or moderate-to-vigorous PA (MVPA) using five cut-off points: Puyau, Evenson, Romanzini, Clanchy and Baque. The predicted EE was computed using three AG-based equations (Freedson, Trost and Treuth) and an AP step-based equation. The classification accuracies of the five AG cut-off points were assessed using Spearman correlation (r) and kappa (κ) coefficients. Agreements between measured and predicted EE values were assessed using paired-t tests, mean differences (95% confidence interval) and Bland-Altman plots. RESULTS: Of the five AG cut-off points, Baque (r = 0.896, κ = 0.773) and Clanchy (r = 0.935, κ = 0.721) classified PA and ST most accurately. All the equations overestimated EE during sitting activities and underestimated EE during rapid walking. Across all activities, the mean bias and 95% limits of agreement for the Freedson, Trost, Treuth and AP prediction equations were -0.05 METs (-2.15, 2.05), -0.28 kcal·min-1 (-2.18, 2.74), -0.54 METs (-2.37, 1.29) and 0.04 METs (-2.60, 2.68), respectively. The Freedson, Treuth and AP equations exhibited systematic bias during rapid walking, as their differences from the criterion measure increased progressively with increasing activity intensity. CONCLUSION: The AG accurately classified PA and ST when the Baque and Clanchy cut-off points were used. However, none of the available AG or AP equations accurately predicted the EE during PA and ST in children and young adults with CP. Further development is needed to ensure that both devices can estimate EE accurately in this population.