True Fitness Z9, Z8 manual Appendix A - Target Heart Rate Chart, Contact Heart Rate Monitoring

Appendix A - Target Heart Rate Chart

Contact

Heart Rate

Monitoring

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 sys- tems. This is also the reason why CHR systems must typically 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 up- per-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.

Z 8 a n d Z 9 S e r i e s Tr e a d m i l l O w n e r ' s G u i d e

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