The EKG sensor measures cardiac
waveforms generated by electrical activity of the heart muscle. The cyclical
contraction and relaxation of the atria and ventricles involves polarisation
and depolarisation of heart muscle fibres. This creates an electrical current
that moves through the body, and which can be measured by electrodes attached
to the skin.
The subject should be stationary when making
the measurements, but interesting comparative data may be collected before
and after exercise. Other interesting investigations involve placing the electrodes
at different places on the body to determine the axis of the heart, and studying
the change in the waveforms before and after the ingestion of mild stimulants
(e.g. caffeinated coffee or cola).
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