HRV Metrics

Understanding your heart data

Learn what each HRV metric means and how CardioMood translates complex data into actionable insights for your health.

Actionable Insights

Your daily health scores

CardioMood transforms raw HRV data into easy-to-understand scores that guide your daily decisions.

0-100

Readiness Score

A composite score (0-100) combining overnight HRV, sleep quality, and recovery patterns to indicate your body's readiness for physical and mental demands.

0-100

Stress Index

Real-time measurement of physiological stress based on HRV patterns. Helps identify when you're under pressure before you feel it.

0-100%

Recovery Index

Tracks your recovery trajectory after exercise or stress, comparing current HRV to your personal baseline.

0-100

Sleep Quality

Overnight HRV analysis reveals sleep stage quality, autonomic balance during sleep, and overall restorative value.

Time Domain

Beat-to-beat analysis

Time domain metrics analyze the intervals between heartbeats, providing direct measures of heart rate variability.

RMSSD

Root Mean Square of Successive Differences
Unit
ms
Typical Range
20-100 ms

The most common HRV metric, RMSSD measures beat-to-beat variation and reflects parasympathetic nervous system activity. Higher values indicate better recovery and lower stress.

Interpretation: Higher is generally better, indicating good vagal tone and recovery capacity.

SDNN

Standard Deviation of NN Intervals
Unit
ms
Typical Range
50-150 ms

Reflects overall HRV and is influenced by both sympathetic and parasympathetic activity. A global indicator of autonomic nervous system health.

Interpretation: Higher values suggest greater adaptability and resilience.

pNN50

Percentage of NN50
Unit
%
Typical Range
3-30%

The percentage of successive RR intervals that differ by more than 50ms. Another marker of parasympathetic activity.

Interpretation: Higher percentages indicate stronger parasympathetic influence.
Frequency Domain

Spectral analysis

Frequency domain analysis breaks down HRV into different frequency bands, each reflecting different aspects of autonomic regulation.

LF Power

Low Frequency Power (0.04-0.15 Hz)
Unit
ms²

Reflects a mix of sympathetic and parasympathetic activity. Associated with blood pressure regulation and baroreceptor activity.

Interpretation: Context-dependent interpretation; not purely sympathetic as once believed.

HF Power

High Frequency Power (0.15-0.40 Hz)
Unit
ms²

Primarily reflects parasympathetic (vagal) activity and is synchronized with respiration (respiratory sinus arrhythmia).

Interpretation: Higher values indicate stronger parasympathetic influence.

LF/HF Ratio

Low Frequency to High Frequency Ratio
Unit
ratio

Historically used as a marker of sympathovagal balance, though modern research suggests more nuanced interpretation.

Interpretation: Lower ratios generally indicate parasympathetic dominance.
Important Context

HRV is personal

Your HRV values are unique to you. What matters most is not comparing to others, but understanding your own patterns and trends over time.

  • Age matters: HRV naturally decreases with age. A 50-year-old's "normal" is different from a 25-year-old's.
  • Trends over absolutes: A 10% drop in YOUR HRV is more meaningful than comparing to population averages.
  • Context is key: HRV varies with sleep, stress, exercise, and lifestyle. Consider the full picture.
Your 7-Day HRV Trend
MonTueWedThuFriSatSun
Weekly average52 ms

Ready to understand your HRV?

Get personalized insights and track your health metrics with CardioMood.