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Many definitions of heart rate are possible. This study makes use of
both instantaneous heart rate, , and mean heart
rate,
, as defined below.
Given the sequence of beat arrival times , where denotes
the beat number, a uniformly sampled instantaneous heart rate signal
may be defined as

(1) 
where is the desired sampling interval for , is a
smoothing parameter, and and have been chosen such that

(2) 
The middle term () in equation (1) thus represents one more than
the number of complete interbeat intervals within a window of width centered on ; the first term is the fraction of the previous
interval within the window, and the last term is the fraction of the final
interval that falls outside the window. From the instantaneous rate
, we derive the mean heart rate:

(3) 
In the present study,
seconds, , and (i.e.,
mean heart rate is determined over a period of
minutes).
Next: Correlates of physical activity
Up: ECGbased Indices of Physical
Previous: Introduction
George B. Moody
20020418