WTF is HRV

Heart Rate Variability (HRV): What it is and why it should matter to you

WHAT

The gap between each heartbeat is not constant and changes depending on psychological and physical factors.

This variation in time between each heartbeat is known as Heart Rate Variability (HRV).

Having variation between each heartbeat is a positive sign. Indicating good cardiovascular fitness and a healthly and responsive Autonomic Nervous System (refresher on this).

Changes in HRV indicates which branch of the Autonomic Nervous System is dominant at that time.

When HRV is high, it indicates the Parasympathetic Nervous System (PNS) is dominant and the body is relaxed. For example, whilst we are asleep.

When HRV is low, it indicates the Sympathetic Nervous System (SNS) is dominant and we are experiencing a stress response. For example, whilst in an intense meeting or sitatuation.

(Clearly J Biebs is very interested in HRV)

HOW DO WE KNOW THIS

When the PNS is dominant and we are relaxed, heart rate is typically lower. Therefore, because the heart is beating less frequently, there is more opportunity for there to be variation between each heartbeat.

Conversely, when the SNS is dominant, heart rate is typically higher due to adrenaline secreted during a stress response. Therefore, because the heart is beating more constantly, the opportunity for variation between each beat is not as available.

Hence, high HRV indicates a relaxed state and low HRV is a sign that the body is under stress.

THE GOAL

On average, to have HRV within or above the range for your age, shown below in the graphic.

Short term, having a lower HRV, like when exercising intensely, is not necessarily a bad thing. It can be a sign you are pushing yourself and your body will adapt and improve over time.

However, a HRV consistently lower than the range for your age can indicate you are taking on a lot of stress without adequate recovery, potentially leading to burnout in the long-term if not addressed.

HOW TO IMPROVE HRV

It can be done through lifestyle.

This (non-exhuastive) list includes: regular cardio and strength training, breathwork, meditation, consistent quality sleep, balanced nutrition, social connection, stress reduction techniques and adequate hydration.

It is also important to recognise that stressors, stimulants and depressants will negatively impact HRV.

This includes alcohol consumption, caffeine and tobacco since they will trigger a stress response (decreasing HRV).

Sorry Merry, that does mean less pints.

DISC

HRV is very individualised and many things can influence it such as age, gender, genetics and lifestyle. Daily fluctuations do not necessarily highlight anything significant.

So, when tracking HRV (I use a WHOOP) focus on longer-term trends over weeks or months.

Generally speaking, if your average monthly HRV is within, or above, the range for your age group it indicates good cardiovascular fitness and a responsive stress response system.

PLEASE NOTE

I research each topic thoroughly before sending each newsletter. However, by its very nature, the science on the subjects I discuss is ever evolving. The information, at the time of sending, was accurate to the best of my knowledge.

The information contained in this newsletter is not medical advice and I am not medically qualified. You should always research independently or consult a medical professional before making any changes to your lifestyle, including on the subject discussed here.

Further, some heart conditions, such as atrial fibrillation (AF), will render HRV readings obsolete or unreliable and therefore the above information useless.

Sources for this installment of Marginal Steps:

(Yamanaka et al., 2015)

(Seol et al., 2020).

TL;DR

HRV is a measurement of the variation in time (ms) between each heartbeat.

If HRV is within or above the range for your age it can indicate good fitness and a robust ability to handle stressors.

If HRV is low, relative to you and your age range, it can indicate you are taking on a lot of stress without adequate recovery and should seek to address this imbalance.

HRV can be improved through lifestyle changes like exercise, avoiding stimulants/depressants and good sleep.