Defining ambulatory bouts in free-living activity: Impact of brief stationary periods on bout metrics

The aim of this study was to assess the effect of varying the maximum resting period between consecutive ambulatory bouts in community-based outcomes. Ambulation was assessed in 97 community-dwelling older adults (mean (SD) age 69.2 (7.7) years) using an accelerometer (activPAL (TM)) worn on the upper thigh for 7 consecutive days. The volume, pattern and variability of ambulation were calculated over a range of maximum resting periods (1-30 s). Outcomes with a maximum resting period from 1 to 6 s did not vary due to device functionality. Non-linear regression (power law, r(2) > 0.99) showed that increasing the maximum resting period from 6 to 30 s resulted in changes in volume (increased duration spent walking, and decreased number of bouts), variability (S-2 increased) and pattern (alpha decreased), and a linear relationship with an increase in average bout length. With a MRP of 6s,6% of the cohort achieved the public health guidelines of 150 min of ambulation/week accumulated in bouts >= 10 min, which increased to 40% using a maximum resting period of 30s. Modifying the maximum resting period impacts on volume, pattern and variability measures of community based ambulation, and attainment of public health guidelines. This highlights the need for standardised algorithms to aid interpretation and explicit reporting of the maximum resting period to aid comparison between studies. (C) 2015 Elsevier B.V. All rights reserved.