Assessment of minute-by-minute stepping rate of physical activity under free-living conditions in female adults

Background: The minute-by-minute stepping rate (MMSR) is a unique index of the walking speed. The MMSR under free-living conditions remains unclear. Purpose: The purpose of the present investigation was to clarify the physical activity (PA) levels based on MMSR under free-living conditions. Methods: A total of 85 female volunteers, age from 21 to 91 year, wore a pedometer with a uni-axial accelerometer (Lifecorder, Kenz, Japan) for 7 days consecutively in order to determine the number of steps, the intensity of PA (light intensity PA; LPA, moderate intensity PA; MPA, and vigorous intensity PA; VPA), and the MMSR. Thereafter, the daily time spent in PA at < 100, 100 to 129, and 130 steps min(-1) (min day(-1)) was calculated. All experiments were conducted in March 2007. Results: The number of steps, the time spent in LPA, MPA, VPA, PA at < 100, 100 to 129, and 130 steps min(-1) were 9275 +/- 3453 steps day(-1), 71 +/- 25 min day(-1), 34 +/- 22 min day(-1), 4 +/- 6 min day(-1), 295 +/- 88 min day(-1), 16 +/- 12 min day(-1), and 4 +/- 6 min day(-1). The time spent in PA at < 100 steps min(-1) positively associated with age (p < 0.05). The time spent in PA at 100 to 129 steps min(-1) negatively associated with age (p < 0.01). Conclusion: The time spent in PA at < 130 of steps min(-1) MMSR differs across different age-groups under free-living conditions in female adults. The clinical significance with regards to the age-associated changes in MMSR remains unclear. (c) 2011 Elsevier B.V. All rights reserved.