What Is Heart Rate Variability?

By Jonathan Davenport, CSCS, TSAC-F, CCC, CPT
A look into HRV and how this metric may be extremely valuable for increases in aerobic fitness and health.

HRV, or Heart Rate Variability, is the measurement in time intervals that elapses between consecutive heart beats (measured in milliseconds). In other words, it measures the differences in the duration between each heartbeat.

HRV is an important indicator of the Autonomic Nervous System (ANS) activity, which controls various involuntary bodily functions. The ANS has two primary branches: the sympathetic nervous system (the “fight or flight” response) and the parasympathetic nervous system (the “rest and digest” response).

Learn More: Understanding the Autonomic Nervous System: The Difference Between the Sympathetic & Parasympathetic System… Coming soon

Here are some significant factors regarding HRV and how it can be utilized for increasing the health-span:

  1. Health and Well-being: HRV is often associated with overall health and well-being. Higher HRV is generally indicative of better health, while lower HRV may suggest physiological or psychological stress, illness, or impaired functioning of the autonomic nervous system. [5]
  2. Autonomic Balance: HRV provides insights into the balance between the sympathetic and parasympathetic branches of the autonomic nervous system. An optimal balance between these systems is crucial for maintaining various physiological processes, including cardiovascular function, immune response, digestion, and emotional regulation. [1]
  3. Stress Assessment: HRV is widely used as a non-invasive measure of stress levels. Higher stress levels are often associated with reduced HRV, indicating a dominance of sympathetic activity and limited parasympathetic influence. [2]
  4. Fitness and Training: HRV monitoring is commonly employed in sports and fitness settings to assess an individual’s readiness for physical activity and recovery. It can help determine the appropriate intensity and duration of training sessions by considering the body’s physiological state. [3]
  5. Mental Health: HRV has been studied in relation to mental health conditions such as anxiety, depression, and post-traumatic stress disorder (PTSD). Altered HRV patterns have been observed in individuals with these conditions, highlighting its potential as a biomarker and a tool for monitoring treatment effectiveness. [4]
  6. Chronic Conditions: HRV analysis has shown promise in various chronic conditions, including cardiovascular diseases, diabetes, and respiratory disorders. Monitoring HRV can provide insights into the progression and management of these conditions. [5]
Learn More: Using HRV for Fitness & Performance… Coming soon

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  1. Laborde S, Mosley E, Thayer JF. Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research – Recommendations for Experiment Planning, Data Analysis, and Data Reporting. Front Psychol. 2017 Feb 20;8:213. doi: 10.3389/fpsyg.2017.00213. PMID: 28265249; PMCID: PMC5316555.
  2. Carney RM, Blumenthal JA, Freedland KE, Stein PK, Howells WB, Berkman LF, Watkins LL, Czajkowski SM, Hayano J, Domitrovich PP, Jaffe AS. Low heart rate variability and the effect of depression on post-myocardial infarction mortality. Arch Intern Med. 2005 Jul 11;165(13):1486-91. doi: 10.1001/archinte.165.13.1486. PMID: 16009863.
  3. Djaoui L, Haddad M, Chamari K, Dellal A. Corrigendum to “Monitoring training load and fatigue in soccer players with physiological markers” [Physiol. Behav. 181 (2017) 86-94]. Physiol Behav. 2018 Oct 1;194:589. doi: 10.1016/j.physbeh.2018.02.041. Epub 2018 Mar 4. Erratum for: Physiol Behav. 2017 Nov 1;181:86-94. PMID: 29514736.
  4. Schneider M, Schwerdtfeger A. Autonomic dysfunction in posttraumatic stress disorder indexed by heart rate variability: a meta-analysis. Psychol Med. 2020 Sep;50(12):1937-1948. doi: 10.1017/S003329172000207X. Epub 2020 Aug 28. PMID: 32854795; PMCID: PMC7525781.
  5. Jarczok MN, Weimer K, Braun C, Williams DP, Thayer JF, Gündel HO, Balint EM. Heart rate variability in the prediction of mortality: A systematic review and meta-analysis of healthy and patient populations. Neurosci Biobehav Rev. 2022 Dec;143:104907. doi: 10.1016/j.neubiorev.2022.104907. Epub 2022 Oct 13. PMID: 36243195.