Measuring Activity Energy Expenditure with the Actiheart
The Actiheart is a compact, chest-worn device that records heart rate and physical activity in one combined, light-weight waterproof unit and uses a system of branched modelling to use both the activity and heart rate to calculate Activity Energy Expenditure (AEE).
How does it work?
The Actiheart is worn on either two standard ECG pads on the chest or on a belt similar to a Polar wearlink belt. For more information please see the page on wearing the Actiheart.
The Actiheart simultaneously records activity and heart rate and uses both parameters to calculate Activity Energy Expenditure (AEE). By combining both activity and heart rate, the accuracy of the energy expenditure calculation is substantially improved over using just activity or just heart rate alone. Energy Expenditure calculations are within 0.02kJ/kg/min of those measured by a Cosmed K4b23
Details of the system of branched modelling used in the Actiheart are shown below in figure 1. Full details are given in the Actiheart User Manual and links to papers validating the branched model can be found in the Actiheart Bibliography.
The Actiheart has been validated against Doubly Labelled Water for measuring AEE and is the acknowledged standard for ambulatory AEE measurement.
How is the data displayed?
Data from the Actiheart is transferred via the reader/charger to the Actiheart software for analysis. Examples of the way the AEE data is displayed are shown below:
Example screenshot from Actiheart Software Daily Energy Expenditure Analysis window
Example screenshot from Actiheart Software Activity Energy Expenditure Analysis window
|REE:||Resting Energy Expenditure (derived from Schofield Equations or an entered measured value)|
|AEE:||Activity Energy Expenditure (calculated using the branched model equations)|
|DIT:||Dietary Induced Thermogenesis (factored in as a constant of 10% of TEE)|
|TEE:||Total Energy Expenditure (REE + AEE + DIT)|
|PAL:||Physical Activity Level (TEE/REE)|