Reliably estimating ambulatory activity in youth with arthrogryposis

Quantification of the physical activity levels using pedometers and accelerometers in children and adolescents with mobility limitations has recently allowed researchers and practitioners to track real-life outcomes of new interventions in this particular population. Questions remain concerning the reliability of ambulatory activity monitoring in functionally challenged youth. The purpose of the analysis, therefore, was to document the minimal number of days required to reliably estimate ambulatory activity levels in children with arthrogryposis.

Thirteen boys and girls with arthrogryposis (average age 10.9 years) completed stepping activity monitoring using a two-dimensional accelerometer over a period of up to 15 consecutive days. Generalizability theory was applied to identify sources of variance in daily step counts (generalizability study, G study) and to determine the number of days necessary to obtain a reliable coefficient of ≥0.80 (decision study, D study).

G study results showed that intra-individual variability was larger (58.4% of total variance) than inter-individual variability (28.7% of total variance). D study indicated that 9 days of monitoring was required to reach a stable measure of ambulatory activity.

Due to relatively greater variability in step counts across days of the week, a longer monitoring period was required for youth with arthrogryposis. Implication for Rehabilitation Large proportion of variance in daily step counts was attributable to unidentifiable sources of variance, suggesting further exploration of factors that influence on the walking activity in youth with arthrogryposis. Step activity monitoring of youth with arthrogryposis should occur over a 9-day period to reliably capture their habitual level of ambulation. Rehabilitation programs aimed to promote increased stepping in youth with arthrogryposis which can utilize the findings of the present study to appropriately track their effectiveness.