An Accelerometry-Based Approach to Assess Loading Intensity of Physical Activity on Bone

Purpose: The purpose was to develop a new method for assessing the potential bone-loading intensities of different locomotion activities by using accelerometers. Method: Thirty participants (women, N=19; men, N=11) with an average age of 40 years (SD=18 years), performed 8 activities (3 self-selected speeds of walking, 3 self-selected speeds of running, and ascending and descending stairs) in the workplace or at home while wearing an accelerometer. The loading intensity for each activity was calculated from measured acceleration by a new method that considers both loading magnitude and frequency. A 1-way repeated-measures analysis of variance was employed to examine whether type of activity had any significant influence on the loading intensity. Results: The 8 activities showed different loading intensities (p<.001, partial (2)=.87). Running had higher loading intensity than walking and ascending or descending stairs (p<.05, Cohen's d=1.79). The higher the speed of walking or running, the higher the loading intensity (p<.05, Cohen's d=1.15). The increase of loading intensity in different activities was induced by both the increase of loading magnitude and the shift of loading frequency. Conclusions: This study developed a new method to measure loading intensity of physical activity on bone by using an accelerometer. This method can provide new insight for the assessment of exercise intensity in relation to bone health.