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.