Understanding HRV readiness score

Heart Rate Variability (HRV) serves as a potent indicator of physiological readiness, shedding light on the body’s capacity to confront daily challenges and manage stress. By examining the time variations between heartbeats, HRV acts as a lens into the autonomic nervous system’s equilibrium, signifying our potential for resilience and recovery.

This article seeks to elucidate the principles of readiness assessment through HRV and aid in interpreting the readiness score. We will delve into how HRV fluctuations relate to stress, recovery, and overall well-being, enabling you to make well-informed choices regarding training, rest, and lifestyle modifications for prime performance and health.

Whether you’re an athlete optimizing training intensity, a professional navigating stress, or simply keen on personal wellness, grasping your HRV and readiness index can transform your approach to achieving balance and optimal condition.

Kubios HRV Readiness index

HRV during rest and recovery

In rest and recovery phases, the autonomic nervous system leans towards parasympathetic dominance, often described as the “rest and digest” state. This transition fosters relaxation, digestion, and healing. A decelerated heart rate and elevated HRV mark this phase, indicating increased variability between heartbeats. HRV levels during rest vary among individuals, with higher values generally associated with younger age, superior cardiovascular fitness, and enhanced well-being. Thus, accurate readiness monitoring necessitates historical HRV data for comparison. Elevated HRV relative to your historical data denotes heightened physiological readiness.

HRV during stress

Stress activates the sympathetic nervous system, igniting the “fight or flight” response. This condition primes the body to tackle perceived threats by elevating heart rate, blood pressure, and muscle preparedness, concurrently reducing HRV to denote diminished beat-to-beat variability. Lower HRV in stressful situations signals a constrained adaptability to challenges, potentially underscoring health concerns or the need for refined stress management tactics. Reduced HRV compared to your historical norms indicates decreased physiological readiness and escalated stress levels.

Readiness index

The Readiness Index evaluates your physiological state by comparing your current resting HRV against your customary levels. For calculating the readiness index, the parasympathetic nervous system index (PNS index), which accurately mirrors parasympathetic system alterations, is preferred over singular HRV metrics like RMSSD.

The Readiness Index categorizes into VERY LOW, LOW, NORMAL, and HIGH, mirroring deviations from your average HRV:

  • VERY LOW – Significantly lower than usual (only 2-3% of your results). This indicates reduced parasympathetic nervous system activity, suggesting high stress or fatigue levels.
  • LOW – Below normal (about 14% of your results). A low score reflects somewhat decreased parasympathetic activity, which could be a response to moderate stress.
  • NORMAL – Within your typical range (around 68% of your results). This indicates balanced parasympathetic nervous system activity, reflecting normal recovery and stress levels.
  • HIGH – Above normal (approximately 16% of your results). A high score often signifies enhanced parasympathetic activity, suggesting optimal recovery and lower stress levels.

Consistent daily measurements enhance initial accuracy, utilizing up to 90 days of historical data. This dynamic index provides tailored insights into your readiness, advising on optimal stress management and recuperation strategies.

HRV Readiness score

Figure: HRV morning readiness score with Kubios HRV app.

Taking a new readiness measurement

For dependable HRV measurements, consistency is key. It is recommended to:

  • Adopt a specific position (ideally reclined or semi-reclined) at a set time (preferably in the morning upon waking) and minimize all disturbances.
  • Remain relaxed and breathe normally during the measurement, without speaking. The app will notify you upon completion.
  • Verify the quality of the measurement afterward. If quality is notably low, retake the measurement (possibly after moistening the electrodes).

Measurement duration can range from 1-5 minutes, with durations over 3 minutes recommended for increased accuracy. Prior to measuring, a brief period of relaxation (at least 15-30 seconds) ensures resting conditions. Regular measurements, ideally several times per week, facilitate observation of daily physiological recovery and stress fluctuations, refining the accuracy of weekly averages. Frequent HRV assessments also elucidate how various factors—like physical activity, training, stress, and sleep—affect your HRV, potentially enhancing cardiovascular health.

Understanding the readiness score – How to interpret HRV results?

Note that resting heart rate variability is influenced by numerous personal factors. Normal range of HRV depends, for example, on gender, age, cardiorespiratory fitness, cardiovascular system health, and certain medication uses. Thus, initial resting HRV measurements alone cannot provide a dependable readiness assessment. A history of 1-2 weeks of resting HRV data is essential for a meaningful evaluation.

Be aware that while resting HRV yields reliable information about the physiological readiness, it is sensitive to many factors affecting overall bodily stress. For instance, a low readiness score in the morning could stem from various causes:

  • Poor sleep quality for any reason (late nights, alcohol consumption, disturbances by small children, etc.) [5]
  • Incomplete recovery from intense exercise [2]
  • Insufficient recuperation from excessive work-related stress [3], [4]
  • Psychosocial stress or familial issues [1]
  • Onset of illness and inflammation [6]
  • Any other stressors that increase sympathetic nervous system activity.
HRV recovery monitoring

Figure: Example of daily recovery monitoring with Kubios HRV Team Readiness software.

Differentiating acute and chronic fatigue

It’s vital to distinguish between acute and chronic fatigue due to their different scales and severity. Acute fatigue results from short-term stressors, like intense training or high workloads, leading to temporary stress accumulation. Given that the accumulation of stress continues only a few days or 1-2 weeks at most, with sufficient rest, one can usually restore their stress-recovery balance and regain normal readiness within days. For athletes, acute decreases in HRV post-exercise are normal, but HRV-guided training can optimize recovery and performance by adjusting training intensity based on HRV levels [2].

Chronic fatigue emerges from prolonged stress exposure, significantly affecting health with risks like cardiovascular disease, depression, inflammation, and metabolic disorders [3]. It indicates a deeper, more serious imbalance, potentially signaling over-training in athletes. Recovering from chronic fatigue requires a much longer period, emphasizing the importance of HRV monitoring to avert long-term detriment to health.

What is a good HRV while sleeping?

In general, heart rate is low and heart rate variability is high during nighttime. During sleep, the parasympathetic nervous system activity dominates, lowering heart rate, body temperature, and relaxing muscles. Our heart rate while sleeping can be 20-30% below the resting HR measured during daytime.

Higher HRV during nighttime has been linked to deeper sleep stages, while during REM sleep increased sympathetic activity may lower HRV [9]. If variability of heart rate is abnormally low at night, it is an indication of poor sleep quality and possible sleep disorder. [7]

Frequently Asked Question (FAQ)

How is the readiness index calculated?

The readiness index is calculated by comparing your current resting HRV against your customary resting HRV values from the past 3 months. Instead of a singular HRV metric like RMSSD, the calculation uses the PNS index, which accurately reflects parasympathetic nervous system activity.


What affects the accuracy of the readiness index?

To accurately measure your resting HRV, the measurement duration should be at least 3 minutes. Regular measurements, preferably taken daily, are essential to form a solid baseline of your normal resting HRV levels. Additionally, the measurements should be performed consistently every day, avoiding any disturbances.


How should I measure my readiness or recovery?

Consistency is key when monitoring your readiness or physiological recovery using resting HRV measurements. We recommend taking the measurement in the morning upon waking, in a reclined or semi-reclined position. Breathe normally during the measurement and avoid speaking, as it can alter your normal respiration.


Should I be worried if I get a low readiness score?

It is quite normal to occasionally get a lower readiness score. A low readiness index value means that your parasympathetic nervous system activity is decreased compared to your baseline, which can be a response to moderate physical or mental stress. Sleep quality also affects your readiness score, so a low score may be explained by a poorly slept night.


Readiness index and physiological recovery?

If you are an athlete who trains frequently, monitoring your physiological recovery status with the readiness index can be beneficial. Intermittent low readiness scores after hard training sessions are normal and nothing to worry about. However, a longer-term decreasing trend in your readiness score may indicate a lack of physiological recovery and could suggest you are on the path to overtraining.


  1. A. Brugnera, C. Zarboa, M.P. Tarvainen, P. Marchettinic, R. Adornia, and A. Compare. Heart rate variability during acute psychosocial stress: A randomized crossover trial of verbal and non-verbal laboratory stressors. Int J Psychophysiol, 127:17-25, 2018.
  2. A. Granero-Gallegos, A. González-Quílez, D.Plews, and M. Carrasco-Poyatos. HRV-Based Training for Improving VO2max in Endurance Athletes. A Systematic Review with Meta-Analysis. Int J Environ Res Public Health, 17 (7999):1-21, 2020.
  3. S. Järvelin-Pasanen, S. Sinikallio, and M.P. Tarvainen. Heart rate variability and occupational stress–systematic review. Industrial Health, 56:500-511, 2018.
  4. S. Sammito, B. Thielmann, A. Klussmann, A. Deußen, K.-M. Braumann, and I. Böckelmann. Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science. J Occup Med Toxicol, 19(15):1-29, 2024.
  5. P.K. Stein and Y. Pu. Heart rate variability, sleep and sleep disorders. Sleep Med Rev, 16(1):47-66, 2012.
  6. D.P. Williams, J. Koenig, L. Carnevali, A. Sgoifo, M.N. Jarczok, E.M. Sternberg, J.F. Thayer. Heart rate variability and inflammation: A meta-analysis of human studies. Brain Behav Immun, 80:219-226, 2019.