The use of accelerometers for the measurement of physical activity in children has increased substantially over the last several years. Accelerometers are typically worn on the waist and they have internal clocks and large memory capacities making them well suited as a non-invasive objective method of tracking physical activity patterns for days to weeks. Typically, accelerometer data (counts) are converted to estimates of energy expenditure or time spent in light, moderate and vigorous physical activity, by using single linear regression equations relating counts to energy expenditure. In addition, the equations developed for adults are not applicable to children since the relationship between counts and energy expenditure is affected by factors such as age and body mass. Recently members of this research group have developed a 2-regression model, for use in adults, which distinguishes walking and jogging from intermittent lifestyle activities based on the variability in the accelerometer counts. The 2-regression model provided a significant improvement in the accuracy and precision of estimating energy expenditure and time spent in light, moderate, and vigorous physical activity, in adults. This proposal will address the needs of extending the more advanced methods used to analyze accelerometer data in adults to children.
The specific aims of the study are to: 1) Develop a 2- regression model in children 8-9 years of age (n=120) using 10 minute bouts of 18 structured activities that will range from sedentary behaviors to vigorous physical activities;and 2) Validate the new 2-regression model in a separate sample of children 8-9 years of age (n=72) using seven activities performed for 10 minutes each and 2 hours of free-living activity. The overall goal of the project is to develop a 2-regression model that will improve the accuracy and precision for estimating energy expenditure and time spent in light, moderate, and vigorous physical activity in children 8-9 years of age. In addition, during the development and validation of the 2-regression model, we will include equal numbers of normal weight children (BMI <85th percentile, age and sex specific) and overweight and obese children (BMI >85th percentile, age and sex specific). This will allow for further understanding about how factors such as weight and body composition affect the relationship between accelerometer counts and energy expenditure. The methodologies developed in this study will then be used for future research examining a larger age group (e.g., 6-18 years of age) with a wide range of body sizes and race/ethnicities.
Over the last 20 years obesity has more than doubled in school-aged children and is a serious public health concern. Physical activity plays an important role in the prevention and treatment of obesity and other metabolic disorders. This study will provide improved methods for physical activity assessment in children.
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| Crouter, Scott E; Horton, Magdalene; Bassett Jr, David R (2012) Use of a two-regression model for estimating energy expenditure in children. Med Sci Sports Exerc 44:1177-85 |
