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This paper describes a method to evaluate daily physical activity by means of a portable device that determines the type of physical activity based on accelerometers and a barometer. Energy consumption of a given type of physical activity was calculated according to relative metabolic ratio (RMR) of each physical activity type that reflects exercise intensity of activities. Special attention was paid to classification algorithms for activity typing that identify detailed ambulatory movements considering vertical movements, such as stair/ slope climbing or use of elevators. A portable measurement device with accelerometers and a barometer, and a Kalman filter was designed to detect the features of vertical movements. Furthermore, walking speed was calculated by an equation which estimates the walking speed as a function of signal energy of vertical body acceleration during walking. To confirm the usefulness of the method, preliminary experiments were performed with healthy young and elderly subjects. The portable device was attached to the waist. A standard accelerometer based calorie counter was also attached for comparison. Experimental results showed that the proposed method feasibly classified the type of ambulatory physical activities; level walking, stair going up and down and elevator use. It was suggested that the consideration of vertical movements made a significant improvement in the estimation of energy consumptions, and the proposed method provides better estimation of physical activity compared to the conventional calorie counter.

This study presents an assessment of walking stability in elderly people, focusing on local dynamic stability of walking. Its main objectives were to propose a technique to quantify local dynamic stability using nonlinear time-series analyses and a portable instrument, and to investigate their reliability in revealing the efficacy of an exercise training intervention for elderly people for improvement of walking stability. The method measured three-dimensional acceleration of the upper body, and computation of Lyapunov exponents, thereby directly quantifying the local stability of the dynamic system. Straight level walking of young and elderly subjects was investigated in the experimental study. We compared Lyapunov exponents of young and the elderly subjects, and of groups before and after the exercise intervention. Experimental results demonstrated that the exercise intervention improved local dynamic stability of walking. The proposed method was useful in revealing effects and efficacies of the exercise intervention for elderly people.

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The effects of daily activity and autonomic nerve tone on the fluctuation of ambulatory blood pressure were studied in hypertensive patients. The autonomic nerve tone was measured by frequency domain analysis of the RR interval. Physical activity was evaluated by a walk count, converted to a walk rate (WR), recorded using a digital Holter ECG fitted with an accelerometer, with simultaneous monitoring of blood pressure (Bp). Average values of the WR, H and L/H components were calculated for the 15 min. period just prior to Bp monitoring. The relationship between the average WR, H and L/H values and the Bp was determined by a linear regression analysis. Hypertension was classified into three types, autonomic nerve dominant (AN), exercise dominant (EX), and irregular (IR), based on a high correlation coefficient between Bp and either H or L/H (AN type), between Bp and WR (EX type), or no significant correlation between Bp and any of the parameters (IR type). Of the thirty hypertensive patients studied 11 were classified as AN, 12 as EX, and 7 as IR. Patients of the EX type had significantly lower Bp than patients in the other two classes. Furthermore, all of the IR type patients showed non-dipper type hypertension, suggesting that the Bp regulation mechanisms were impaired. The results suggest the significance of simultaneous monitoring of physical activity and autonomic nerve function at the time of Bp monitoring.