Actiheart User Manual 5.1.31 (Jun 2022)
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are shown derived values of VO2 max. The HR max is obtained from the P max
which is the maximum power that can be produced by stepping. The step size
which is used in the calculations is shown just underneath these values.
The central region of the screen shows the activity data as 15 second black
blocks derived from the Actiheart accelerometer. The additional red line in the
display is by default heart rate in BPM, but can also be selected to show the
Heart Rate Variability per 15 second interval displayed either as max-min or the
Root Mean Square of the beat to beat interval. Any 15 second segment of this
data can be selected with the left mouse button, and viewed in the bottom region
of the screen where ECG is shown along with activity waveform. A segment can
be selected by using the scroll bar or by clicking on the upper graph. The IBI is
accurately derived to within one millisecond using an algorithm to remove noisy
and spurious beats. The actual data values in each 15 second epoch can be
displayed by pressing and holding down the right mouse button whilst scrolling in
the top graph. All the data can be copied to the clipboard.
The lower region of the display shows a summary of the analysis results and
certain options for controlling the calculation of energy expenditure from the step
test results. The meaning of these are discussed further below in
IMPORTANT
If the subjected stopped stepping earlier than the full 8 minutes, the end point of
the test (which is important for the calculation of the recovery) is sometimes
detected incorrectly by the software. It is possible to set the end point manually to
the nearest second in the following manner. Right click in the bottom third of the
screen until only the movement waveform is visible. Then double-click on the
point where the activity ceases; the following message will appear:
Clicking on the Yes option will cause the step test calculation to be updated with
the new end point marked. This end point is marked by a vertical red line on the
main plot, and a blue line in the detailed zoom below when the relevant portion is
selected.
4.5.7 The
Energy
Regression
Equations
The Step Test has a linearly increasing step rate from 15 to 33 step cycles per
minute after the first minute. As the weight and step height are constant, the
energy needed by the user is proportional to the step rate so the energy
expended is also linear during the test. A straight line can therefore be fitted to
the rising portion of the data.
The resulting regression equations are shown at the bottom of the screen. They
are of the form BX+A and these values are displayed along with the R value of
the data. An R value of 1 shows a completely straight line fit of the data. For
details of how the regression equations are arrived at please see
