Actiheart User Manual 5.1.31 (Jun 2022)
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Appendix 7: Glossary of Data Export Terms
This is a list of terms used in the Actiheart software and the data exports from it,
to clarify the meaning of those items.
Activity
An empirical measure of the amount of movement within an epoch, in ‘counts’
per unit of time.
AEE
Activity Energy Expenditure, the portion of energy expended which is above
resting and related to some additional activity.
BMI
Body Mass Index, the weight of a person (in kilograms) divided by the square of
their height (in metres). This is used as a standardised measure of weight which
is compensated for the individuals height.
BPM
The heart rate during a period of time in Beats Per Minute.
Branch
The branch of the model used to weight between activity and heart rate for
calculating energy expenditure. For more details see Appendix 2.
Cal factor
The calibration factor recorded for an Actiheart accelerometer. Each Actiheart is
calibrated during manufacture and the scale level recorded to scale each
recording from it correctly.
DIT
Diet Induced Thermogenesis is a portion of energy expenditure which is used as
part of the process of digesting food or making use of the energy produced. It is
in principle related to the food consumed but is often estimated as it is difficult to
measure and unlikely to change suddenly for an individual.
ECG
Refers to the ElectroCardioGraph, a representation of the electrical signal
detected on the chest electrodes. Actiheart exports with this column header refer
to the magnitude of the electrical signal. This is an approximate measure of the
size of the peak in microVolts, but is not directly calibrated.
Epoch
Short and Long term recordings are divided into “epochs”, fixed periods of 15 to
60 seconds which are summarised by a heart rate and activity level.
HF
The component of the heart rate variability in the High Frequency band. See
VLF for the definitive reference.
HRMax
Maximum heart rate of a user. This may be measured and input directly for the
user, or estimated from their age at the time of a test.
IBI
The Inter-Beat-Interval, usually written in milliseconds, is the time between one
heart beat and the following one. The sequence of these gives the exact timing
of every heart beat rather than just the heart rate
LF
The component of the heart rate variability in the Low Frequency band. See VLF
for the definitive reference.
LF/HF
The ratio between LF and HF heart rate variability. This is a normalised
measure, sometimes described as indicating the balance between sympathetic
and parasympathetic nervous system activity in the body.
