Multiple days of monitoring are needed to obtain a reliable estimate of physical activity in hip-fracture patients.

The aim of the study was to investigate the precision of estimated upright time during one week in community dwelling older adults after hip fracture when monitoring activity for different numbers of consecutive days. Information about upright time was collected by thigh-worn accelerometers during 7 consecutive days in 31 older adults (mean age 81.8 years ± 5.3) 3 months after hip-fracture surgery. Mean time in upright position, including both standing and walking, was 260.9 (± 151.2) min/day. A cutoff value of half an hour was used to provide recommendations about number of recording days. Large variability between participants between days, as well as a nonconstant within-participant variability between days indicates that at least 4 consecutive days of recording should be used to obtain a reliable estimate of upright time for individual persons. However, at a group level, one day of recording is sufficient.