Abstract
Physical activity is known to enhance the mechanical competence of weight-bearing bones, and it is also effective for the prevention of osteoporosis. However, little information is available regarding the optimum exercise and intensity of load to weight-bearing bones as well as about a precise system to monitor the intensity of physical activity. To measure the precise load to weight-bearing bones of exercise as a first step, this study is to evaluate the sampling conditions of data acquisition and develop an accelerometer-based physical activity monitoring and its intensity analysis system. Through a simulation experiment, we found that 1k Hz of sampling rate is possible to achieve a measurement error of less than 2%. With the optimum sampling rate of 1k Hz, we developed an accelerometer-based activity-monitoring system. We then assessed the magnitude of acceleration at the shank, knee, and lumber in healthy subjects (n=19) as they descended stairs. A correlation analysis of the precise acceleration values in three points of the body showed that our system could accurately identify the shock absorptive function of lower extremities. Therefore, we strongly believe that our system, with the optimum sampling rate of 1k Hz, produced an accurate measurement of loads acting on weight-bearing bones.
