True Fitness CSX - Manual (Page 44)

CSX Elliptical Owner’s Guide
44
Appendix A
Contact heart rate monitoring (perhaps more accurately called
hand-touch heart rate monitoring) uses the same principles as
chest strap monitoring: electrically conductive pads detect the faint
electrical signals produced by a beating heart and are converted to a
data signal which can then be displayed digitally as a numeric beats
per minute value.
The only difference is that a chest strap is right next to the heart,
so the signals are relatively strong. Contact heart rate (CHR) using
the fingers and palms receives an inherently much fainter signal.
This is the sole reason for the performance differences between the
two systems. This is also the reason why CHR systems must typi-
cally use two pads per side for a total of four detection pads, while a
chest strap uses just one pad per side; the extra pads are required to
help detect the fainter signal.
The electrical signals detected by heart rate monitoring systems are
a side-effect of the electrical control signals the heart generates to
fire its muscles in the right sequence. The signals start in the top, or
upper-right part of the heart (known as the sinoatrial node), then
travel down to the bottom, or lower-left part of the heart (known as
the Purkinje fibers). It is the fact that the heart is tilted in the chest
cavity, and thus these signals move from the right to the left side of
the body, that makes it possible for monitoring pads on each side
of the body to detect the heart rate. (The CHR pads correspond
roughly to leads I and III in a standard 12-lead ECG setup.)
If a person’s heart is tilted less than average, the signal is weaker.
(Note that this is not indicative of heart strength or health.) In some
people, their heart is nearly vertical in their chest, and even a chest
strap cannot pick up their heart rate signal. (12-pad medical ECG
systems still work well on such an individual.) Less than 1% of the
population are in this category.
Contact
Heart Rate
Monitoring