"Your HRV is lower than usual."
"HRV is higher today."

If you use a health tracker such as an Oura Ring, WHOOP, Apple Watch or Garmin, you've almost certainly seen HRV (Heart Rate Variability) appear alongside your daily recovery score. But what exactly is HRV, and why does it matter?

Heart Rate Variability (HRV) is a measure of the tiny, millisecond-by-millisecond differences in time between consecutive heartbeats. Although your heart may be beating at 60 beats per minute, it doesn't beat exactly once every second. Instead, there are small, natural variations in the time between each beat.

These tiny fluctuations are controlled by your autonomic nervous system (ANS), which regulates many of the body's functions, including heart rate, breathing and digestion. HRV provides valuable insight into the balance between the two parts of this system:

• The parasympathetic nervous system (PNS) – known as "rest and digest" system, is when your heart rate slows and the variation between beats generally increases, resulting in a higher HRV.
• The sympathetic nervous system (SNS) – known as "fight or flight" system is when your heart rate increases and the variation between beats typically decreases, resulting in a lower HRV.

In general, a higher HRV is associated with good recovery, resilience and a well-balanced nervous system. A lower HRV may indicate that your body is under greater stress, whether that's from poor sleep, illness, intense exercise, psychological stress, alcohol consumption or inadequate recovery.

“But my HRV is so much lower than those around me!” If this is you, then don’t worry. It's important to remember that HRV is highly personal and there isn’t a perfect HRV score that everyone should aim for. Your normal HRV is influenced by factors such as age, genetics, fitness level, sleep quality, lifestyle and overall health. Two healthy people of the same age may naturally have very different HRV values.

Rather than comparing your HRV with someone else's, it's far more useful to track your own trends over time. A sudden drop below your normal baseline may suggest your body needs more recovery, while consistently healthy readings often indicate you're coping well with your current training and lifestyle.