The effect of vehicle motion (cab vibration) on accelerometer-cut-point determined MVPA in Heavy Goods Vehicle (HGV) drivers

This study aimed to determine the impact of cab noise when driving Heavy Goods Vehicles (HGV) on cut-point estimated moderate-to-vigorous physical activity (MVPA) from wrist-worn accelerometers. First, we investigated the impact of cab noise on accelerometer output during HGV driving and then on cut-point estimated MVPA in HGV drivers. CAB NOISE: A GENEActiv accelerometer was located beneath the seat in six HGVs for 8-days. Acceleration recorded during driving lay predominantly (~94%) within the sedentary range (<40mg). MVPA: HGV drivers (N=386, 47.9±9.3 years) wore a wrist-worn GENEActiv and a thigh-worn activPAL simultaneously for 8-days covering workdays and non-workdays. MVPA recorded by the activPAL excludes seated transport, thus provided the criterion. Wrist-accelerometer MVPA was classified using two cut-points approximating 3 METs (MVPA100mg) and 4.3 METs (indicative of brisk walking, MVPABRISK_WALK). Acceleration classified as MVPA100mg or MVPABRISK_WALK during activPAL-determined seated transport was considered erroneous.  Across all-days, activPAL MVPA was 15 (IQR: 9, 26) min/day. Compared to activPAL, MVPA100mg was 100 min/day higher (95% limits of agreement (LoA) +/-53 min), but MVPA_{BRISK_WALK} similar (mean bias = -2 min/day, 95% LoA +/- 15). On workdays, 23 (IQR: 11,52) min of MVPA100mg and 2 (1,7) min of MVPA_{BRISK_WALK}, were erroneous. However, on non-workdays, only 4 (3,14) and 0.4 (0,1) min, respectively, were erroneous. In conclusion, MVPA may be erroneously captured using cut-point analyses of accelerometer data in HGV drivers. However, this was substantially reduced by using an MVPA cut-point indicative of brisk walking, which also approximated activPAL estimated MVPA.