POLAR RS 800 SD - Manual (Page 12)

Measuring Heart Rate Variability – R-R Recording
Heart rate varies with every heartbeat. Heart rate variability (HRV) is the
timing between beats, also known as R-R intervals.
An average heart rate of 60 beats per minute (bpm) does not mean that
the interval between successive heartbeats would be exactly 1.0 sec,
instead they may fluctuate/vary from 0.5 sec up to 2.0 sec.
HRV is affected by aerobic fitness and is generally large at rest for a
well conditioned heart. Other factors that affect HRV are age, genetics,
body position, time of day, and health status. During exercise, HRV
decreases as heart rate and exercise intensity increase. HRV also decreases
during periods of mental stress.
HRV is regulated by the autonomic nervous system. Parasympathetic
activity decreases heart rate and increases HRV, whereas sympathetic
activity increases heart rate and decreases HRV.
HRV is used in the OwnZone ®, OwnIndex ® , and in OwnOptimizer™
features. It can also be monitored on its own using the RS800. If your
HRV changes at a given running pace and heart rate, this may indicate
a change in your training load and stress.
Variation in milliseconds between each heartbeat.
RS800 shows SD1
timing in real-time
SD1 is the mean time difference
between maximum & minimum
heart beat intervals.
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