Moving Forward with Backward Compatibility: Translating Wrist Accelerometer Data

PURPOSE: To provide a means for calibrating raw acceleration data from wrist-worn accelerometers in relation to past estimates of children’s moderate-to-vigorous physical activity (MVPA) from a range of cut-points applied to hip-worn ActiGraph data. METHODS: This is a secondary analysis of three studies with concurrent 7-day accelerometer wear at the wrist (GENEActiv) and hip (ActiGraph) in 238 children aged 9-12 years. The time spent above acceleration (ENMO) thresholds of 100, 150, 200, 250, 300, 350 and 400 mg from wrist acceleration data (≤5 s epoch) was calculated for comparison to MVPA estimated from widely used children’s hip-worn ActiGraph MVPA cut-points (Freedson/Trost 1100 counts per minute (cpm); Pate 1680 cpm; Evenson 2296 cpm; Puyau 3200 cpm) with epochs of ≤5, 15 and 60 s. RESULTS: The optimal ENMO thresholds for alignment with MVPA estimates from ActiGraph cut-points determined from 70% of the sample and cross-validated with the remaining 30% were: Freedson/Trost = ENMO 150+ mg, irrespective of ActiGraph epoch (ICC≥0.65); Pate = ENMO 200+ mg, irrespective of ActiGraph epoch (ICC≥0.67); Evenson = ENMO 250+ mg for ≤5 s and 15 s epochs (ICC≥0.69) and ENMO 300+ mg for 60 s epochs (ICC=0.73); Puyau = ENMO 300+ mg for ≤5 s epochs (ICC=0.73), ENMO 350+ mg for 15 s epochs (ICC=0.73), ENMO 400+ mg for 60 s epochs (ICC=0.65). Agreement was robust with cross-validation ICCs=0.62-0.71 and means within |7.8|±4.9% of MVPA estimates from ActiGraph cut-points, except Puyau 60 s epochs (ICC=0.42). CONCLUSION: Incremental ENMO thresholds enable children’s acceleration data measured at the wrist to be simply and directly compared, at a group level, to past estimates of MVPA from hip-worn ActiGraphs across a range of cut-points.