An evaluation of data processing when using the ActiGraph GT3X accelerometer in non-ambulant children and adolescents with cerebral palsy

Purpose: To evaluate vertical acceleration, vector magnitude, non-wear time, valid day classifications, and valid period classifications in the data processing phase when using the ActiGraph GT3X accelerometer in non-ambulant children and adolescents with cerebral palsy (CP).

Material and methods: Accelerometer data retrieved from 33 non-ambulant children and adolescents (4-17 years) with CP were analysed. Comparisons of (i) vertical acceleration versus vector magnitude, (ii) two different non-wear times, (iii) three different settings to classify a day as valid and (iv) two different settings to classify a period as valid were made.

Results and conclusions: Vector magnitude and a non-wear time of at least 90 consecutive minutes statistically significantly increased minutes recorded per day, especially for sedentary time. There was a statistically significant difference in numbers of valid days depending on time criteria set to determine a valid day, whereas there was no statistically significant difference in valid periods using 3 compared to 4 days. This study suggests using the pre-settings in ActiLife; vector magnitude, non-wear time of 90 consecutive minutes, 500 min recorded per day with periods of at least 3 valid days when assessing physical activity objectively by the ActiGraph GT3X accelerometer in non-ambulant children and adolescents with CP.