Significance of Lifestyle Activity in Daily Life Assessed by Triaxial Accelerometer

Abstract

Accelerometers have been used to monitor and assess physical activity. Although several regression equations have been developed to estimate total energy expenditure (EE), it has been shown that no single regression line is able to accurately predict EE across many kinds of physical activities. In addition, some studies have suggested that the intensity of lifestyle activity, such as cleaning and washing, and locomotive activities should be predicted separately. However, there are few approaches to the classification of various physical activities using an accelerometer. PURPOSE: This study: 1) developed a new algorithm for classifying and predicting the physical activity during locomotive and lifestyle activities using a triaxial accelerometer; and 2) investigated the proportional contributions of each of two kinds of activities to EE during a single day. METHODS: In a fasting state, 31 males (42±15 yr) and 35 females (43±13 yr) performed 14 activities wearing a triaxial accelerometer on the left side of the waist, and a mask and Douglas bag to collect expired air. Data were used for the development of the new algorithm. Therefore, other subjects wore a triaxial accelerometer all day for two weeks to evaluate energy expenditure in locomotive and lifestyle activities. RESULTS: Using both sets of synthetic acceleration data with and without a gravity component, lifestyle activity and locomotive activity were classified accurately. In addition, a higher degree of correlation was observed between actual EE and estimated EE using two prediction equations after classification of two activities. The proportional contributions locomotive and lifestyle activity to total EE during a single day were 9.3±3.0% and 22.8±4.7%, respectively. CONCLUSIONS: These findings suggest that our new algorithm for classifying two different types of activities could accurately predict EE for both lifestyle and locomotive activities. Because the EE in lifestyle activity accounts for about 23% during a day, it would be important to accurately evaluate lifestyle activity as well as locomotive activity.