Heart Rate Variability - A Guide To Our Days

In the world of performance, some metrics tell us what we did; but others tell us what we can do. Heart Rate Variability (HRV) belongs in the latter category, offering not just a snapshot of how our body is responding to life, but a guide for how we might best navigate the hours ahead.

If we’re someone seeking better energy and resilience throughout the day, understanding HRV can shift our approach from reactive to responsive.

What Is HRV, Really?

HRV refers to the variation in time between consecutive heartbeats, measured in milliseconds. While it’s easy to assume that a steady rhythm is a sign of health, in reality, a more variable heartbeat (especially at rest) can be a strong marker of physiological adaptability. 1 - link

This variability is governed by the autonomic nervous system, which controls involuntary functions like heart rate, or breathing. It has two branches:

• The sympathetic system - prepares the body for action (fight or flight);

• The parasympathetic system - supports recovery and maintenance (rest and digest).

A high HRV suggests that the body can switch flexibly between these two states depending on internal and external demands. A low HRV, on the other hand, can indicate that the system is under strain (whether due to illness; poor sleep; overtraining; emotional stress; or inflammation, for example).

Why HRV Is So Valuable

Most health markers (like blood tests, or blood pressure) are periodic and static. HRV is dynamic and real-time. This makes it one of the most sensitive indicators of recovery, and resilience and allostatic load (the cumulative burden of chronic stress and life events on the body). Even small daily stressors can add up

By tracking it, we get a better sense of:

• When to push (training; work; or cognitive effort);

• When to pull back (recovery; or nourishment);

• Whether our lifestyle interventions are working;

• How our body is adapting over time.

Interpreting HRV isn’t about obsessing over one number, but about identifying patterns, learning how to align our actions with our physiology.

Many high performers use HRV as a morning check-in:

• A high HRV relative to your baseline may indicate readiness. It’s a good day for physical training; cognitively demanding tasks; or high-output work sessions;

• A low HRV doesn’t mean “do nothing”, but it may be wise to “easier” activities: aerobic movement in zone 2;  breathwork; time outdoors; or simply more buffer between tasks.

This doesn’t require perfection - just intention. The body responds well to rhythms and HRV helps reveal when those rhythms are off.

What Affects HRV & How to Improve It

Several modifiable lifestyle factors influence HRV. Most of them overlap with well-established pillars of health, but HRV provides an objective, day-to-day signal of how effectively they’re working:

• Sleep quality and consistency: sleep is the single biggest HRV determinant. Inconsistent sleep schedules or poor-quality rest can lower HRV dramatically;

• Nutrition and meal timing: heavy meals before bedtime (mainly with an excess of alcohol) and erratic eating patterns all reduce HRV. Conversely, time-restricted eating aligned with circadian biology tends to enhance it; 2 - link

• Exercise: while regular aerobic training (especially in zone 2) improves baseline HRV over time; high-intensity or unstructured training (e.g: in the hours before going to bed) without adequate recovery can acutely suppress it;

• Breathing and mindfulness: slow breathing - particularly techniques like box breathing - stimulate the vagus nerve and boost parasympathetic tone; 3 - link

• Cold exposure and sauna: both can improve HRV if well tolerated and timed appropriately; 4 - link + 5 - link

• Social connection and emotional state: stress isn’t just physical. Chronic emotional strain can lower HRV even in fit individuals. Purpose and supportive relationships promote parasympathetic activation and more stable HRV.

Making HRV Actionable

To make the most of HRV, consistency is key. Choose a reliable wearable and track your baseline over time (at least a couple of weeks), noticing what behaviors consistently improve or degrade it. Use HRV as a conversation with your body, not a scoreboard.

You might discover:

• That evening screen time affects your sleep more than you thought;

• That skipping recovery days lowers HRV more than a hard workout;

• That meditation, even 5 minutes a day, gives your nervous system room to breathe.

Final Thought: A Physiological Compass

We live in a world that can sometimes praise hustle, but the human body doesn’t lie. HRV offers a profound lesson: performance is a reflection of recovery.

Instead of pushing harder through fatigue, it invites us to move more like nature: through cycles of intensity and stillness, activation and restoration. Used well, it doesn’t limit effort; but instead, amplifies it, teaching us when to go, and when to wait.

The result? Fewer crashes; more sustainable energy and a body that’s not just performing; but adapting, and thriving.

References

1 - Shaffer F, Ginsberg JP. An Overview of Heart Rate Variability Metrics and Norms. Front Public Health. 2017 Sep 28;5:258. doi: 10.3389/fpubh.2017.00258. PMID: 29034226; PMCID: PMC5624990.

2 - Chellappa, S.L., Gao, L., Qian, J. et al. Daytime eating during simulated night work mitigates changes in cardiovascular risk factors: secondary analyses of a randomized controlled trial. Nat Commun 16, 3186 (2025). https://doi.org/10.1038/s41467-025-57846-y

3 . Gerritsen RJS, Band GPH. Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity. Front Hum Neurosci. 2018 Oct 9;12:397. doi: 10.3389/fnhum.2018.00397. PMID: 30356789; PMCID: PMC6189422.

4 - Jdidi H, Dugué B, de Bisschop C, Dupuy O, Douzi W. The effects of cold exposure (cold water immersion, whole- and partial- body cryostimulation) on cardiovascular and cardiac autonomic control responses in healthy individuals: A systematic review, meta-analysis and meta-regression. J Therm Biol. 2024 Apr;121:103857. doi: 10.1016/j.jtherbio.2024.103857. Epub 2024 Apr 18. PMID: 38663342.

5 - Laukkanen T, Lipponen J, Kunutsor SK, Zaccardi F, Araújo CGS, Mäkikallio TH, Khan H, Willeit P, Lee E, Poikonen S, Tarvainen M, Laukkanen JA. Recovery from sauna bathing favorably modulates cardiac autonomic nervous system. Complement Ther Med. 2019 Aug;45:190-197. doi: 10.1016/j.ctim.2019.06.011. Epub 2019 Jun 22. PMID: 31331560.

27/06/2025