Summary of the normal values of HRV.
|Component||Outcome parameter||Clinical indication|
|Very low frequency (VLF)||Frequency (0.0033–0.04 Hz)||Indicator of overall activity of various slow sympathetic activities|
|Low frequency (LF)||Frequency (0.04–0.15 Hz)||Indicator of sympathetic activities with parasympathetic influence when the respiration rate is lower than 7 per minute|
|High frequency (HF)||Frequency (0.15–0.4 Hz)||Indicator of parasympathetic activities|
|LF/HF ratio||1.5–2.0||Indicator of sympathetic activities; a higher number means increased sympathetic activities or reduced parasympathetic activities|
|sNormalized LF and HF (LF norm, HF norm)||Frequency (Hz)||The monotonic nonlinear transformation of LF/HF ratio. The LF/HF ratio, LF norm, and HF norm indicate the same aspects of sympathovagal balance of autonomic nervous system|