Physical activity (PA) may need to produce high impacts to be osteogenic. The aim of this study was to identify threshold(s) for defining high impact PA for future analyses in the VIBE (Vertical Impact and Bone in the Elderly) study, based on home recordings with triaxial accelerometers. Recordings were obtained from 19 Master Athlete Cohort (MAC; mean 67.6 years) and 15 Hertfordshire Cohort Study (HCS; mean 77.7 years) participants. Data cleaning protocols were developed to exclude artifacts. Accelerations expressed in g units were categorized into three bands selected from the distribution of positive Y-axis peak accelerations. Data were available for 6.6 and 4.4 days from MAC and HCS participants respectively, with approximately 14 hr recording daily. Three-fold more 0.5−1.0g impacts were observed in MAC versus HCS, 20-fold more 1.0−1.5g impacts, and 140-fold more impacts ≥ 1.5g. Our analysis protocol successfully distinguishes PA levels in active and sedentary older individuals.
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Deere, Hannam, Sayers, and Tobias are with the Musculoskeletal Research Unit, School of Clinical Sciences, University of Bristol, Bristol, UK. Coulson, Ireland, and McPhee are with the School of Healthcare Science, Manchester Metropolitan University, Manchester, UK. Moss, Edwards, Dennison, and Cooper are with the MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK. Lipperts and Grimm are with Atrium Medical Centre, Heerlen, Netherlands.