Calibration and validation of energy expenditure measurement by means of the CUELA Activity Measurement System

Status:

completed 12/2010

Aims:

Energy expenditure has an important function during assessments of occupational tasks. It is used for example to identify heavy and very heavy physical labour. At the same time however, it is a major criterion for quantifying activity and for evaluating measures for promoting activity for the prevention of work-related lack of movement (for example at office workplaces). It is therefore necessary for energy expenditure to be measured as accurately as possible by means of a practicable method. This was to be made possible by means of the CUELA Activity System (cf. IFA Project 4166, "Development of the CUELA Activity Measurement System for the measurement of physical activity") developed at the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA).

Activities/Methods:

For this purpose, a new model approach was developed in which the task detected automatically by the measurement system, the measured kinematic characteristics, and personal data recorded beforehand (sex, age, body-mass index (BMI), heart rate at rest, activity level reported by the subject) were also taken into account. In order for the estimation of the energy exchange performed by the CUELA Activity System to be calibrated and subsequently validated, two studies were conducted with synchronous use of mobile ergospirometry. In both studies, the test subjects performed a standardized set of tasks: these included various office tasks performed in a seated and standing posture, and walking and climbing stairs at different speeds. Eight test subjects took part in the first study. Based upon these data, model formulae were developed for calculating the energy expenditure. In the second study, the accuracy of the energy expenditure estimation was quantified by means of an independent random sample (n=12).

Results:

The validation study showed that the prediction model developed in the project delivers a valid estimation (mean deviation 2.2%) of the energy expenditure for the tasks studied. In future, use of the CUELA Activity System is to enable the energy expenditure to be determined in the course of precise quantification of the level of activity. It is anticipated that the new method employing the CUELA system will on the one hand be substantially more accurate than, for example, estimation of the energy expenditure by means of questionnaires, pedometers or the heart rate, and on the other, will be a more practicable substitute in field use for respiratory gas analysis for determining the energy expenditure (ergospirometry).

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