The ActiheartThe Actiheart MonitorActiheart is a compact, chest-worn device that records heart rate, inter-beat-interval (IBI), and physical activity. Actiheart digitizes the ECG signal and determines the IBI from the R-to-R interval. Through the use of a software program, the user configures the device for data recording. At the time of configuration, the user may determine which combinations of IBI, Heart Rate, and Activity to record on board the monitor for later download. Following the recording session, the data are transferred to the computer for storage, viewing, and analysis. From the IBI recordings, the heart rate and heart rate variability parameters are calculated. Caloric expenditure can be obtained through the use of a software algorithm that combines concurrent heart rate and activity data. Actiheart is the new gold standard for measuring energy expenditure and has been validated against doubly labeled water (publication in press).Applications Sports Medicine and Exercise Science: measurement of heart rate, activity, and energy expenditure Obesity Research: measurement of activity and energy expenditure Stress Monitoring: recording of heart rate and variability during sedentary periods Epidemiology: long-term recording of heart rate and energy expenditure in free-living environmentsActiheart and Energy ExpenditureActiheart easily measures activity and heart rate as well as calculates energy expenditure for ambulatory activities such as bike riding, skate boarding, weight lifting, etc. Using a validated system of branched modeling**, the Actiheart uses both activity and heart rate data to calculate energy expenditure. This increases the accuracy of energy expenditure measurements over systems that use accelerometry data alone. The user has the option of selecting from daily energy expenditure or advanced energy expenditure modes.