If you live by the data on your Apple Watch, Whoop, Oura Ring or any of the other fitness trackers out there, then you’ve probably heard the term “heart rate variability,” or HRV. Still, you may not know exactly what it is or whether you should be paying any attention to it.
While HRV is kind of a big deal when it comes to health and fitness metrics, it’s important to understand how this number fits into the much larger equation. HRV essentially describes the time intervals between consecutive heartbeats, Sherry-Ann Brown, MD, PhD, a cardiologist and owner of My Heart Spark P.C., tells SELF. “It measures how well your nervous system adapts to stress and recovery,” Dr. Brown explains. “A healthy heart naturally speeds up and slows down between beats rather than ticking like a metronome.” In other words, it’s constantly adapting, resulting in greater variability.
On the contrary, low variability can often signal that your nervous system is stuck in fight-or-flight mode or struggling to adapt, says Dr. Brown, which puts constant strain on the heart. And with cardiovascular disease remaining the number one killer of women, responsible for one in three deaths each year, understanding the ins and outs of HRV may prove beneficial.
Here’s everything you need to know about what HRV really means for your health—and a few things you can do to improve it.
What does HRV mean, and why does it matter?
First, let’s talk about what it doesn’t do. HRV does not measure fitness, strength, or performance capacity itself, Joshua Davidson, a lecturer in clinical exercise science at the University of Derby, tells SELF. It’s best to think of it as more of a general recovery indicator that can provide insight into how prepared your body is to tolerate physical strain on any given day.
A higher average HRV is generally associated with better cardiovascular and metabolic health and greater resilience to stress. “A heart that can flexibly adjust its rhythm responds better to exercise, stress, and recovery demands,” Dr. Brown says.
On the other hand, a drop in HRV can help flag when the nervous system is under strain, potentially creating an opportunity for folks to modify training load or intensity before experiencing a dip in performance or an uptick in injury. Other factors like lack of sleep, poor nutrition, and high stress levels also contribute to this overall nervous system strain and can bring down HRV.
Using it as a tool to inform your fitness routine, HRV can help identify how well you’re tolerating your overall load, offering insight into intensity, recovery, and stress management. But it’s important not to give it too much weight; instead, it should just be one part of the equation when it comes to determining your body’s readiness to perform.
“HRV should complement training decisions, not lead them,” says Davidson. You want to consider it alongside objective performance markers like power, speed, and strength, and subjective measures like perceived exertion, muscle soreness, and motivation. Taken together, this can help you create a full picture of your training response and readiness, says Davidson.
Additionally, HRV is most useful when you look at how it trends over time versus focusing on change over the course of a single day. Long-term tracking is what can reveal chronic problems, Alex Rothstein, EdD, CSCS, coordinator and professor for the exercise science program at New York Institute of Technology, tells SELF.
Think about it this way: If you are generally well rested but then get one bad night of sleep, your HRV will likely be all over the place—but chances are you’ll still be able to play a great game of tennis the next day with your friend, Dr. Rothstein explains. It would really come down to how you felt, rather than what your HRV suggested.
That’s why you shouldn’t obsess over short-term changes to your HRV. In fact, day-to-day variability is totally normal. Experiencing a low one after a killer workout, for example, could simply be indicative of training stress. And it’s this challenge on the body that drives strength, cardio, and endurance gains, says Davidson.
What can you do to improve your HRV?
Genetics can dictate whether your HRV naturally tends to be on the higher or lower end, but positive lifestyle choices, including sleep habits, stress levels, and alcohol consumption, can “improve HRV regardless of your genetic starting point,” Dr. Brown says.
Better managing any chronic illness you have, such as diabetes or heart disease, can also improve HRV. And while sleep and stress management typically have the fastest, most measurable impact on HRV (think: a few days) exercise can improve this metric over the course of a few weeks to months, according to Dr. Brown.
Dr. Rothstein agrees. “Doing regular exercise, being more fit, especially if it’s appropriately dosed and you’re not overtraining, will increase your HRV,” he says. Whether it’s a light, relaxing walk in zone 2 or a HIIT workout where you tax the heart, it doesn’t really matter what you choose, Pheonix Carnevale, a NASM-certified trainer and studio leader for Life Time Fitness in New York, tells SELF. They all can move the needle if you’re consistent.
However, just as your fitness regimen can improve your HRV, the opposite can be true. If you overtrain, meaning your training load goes beyond your ability to recover, your nervous system could end up chronically stimulated or fatigued. This can cause your HRV to plummet.
Low HRV becomes a problem when it is prolonged, unplanned, and accompanied by declining performance, persistent fatigue, or poor sleep, Davidson says. “In that context, low HRV may indicate insufficient recovery rather than productive overload. The key distinction is whether suppressed HRV is part of a structured training process with adequate recovery built in,” he explains.
No matter what, Carnevale says you need to prioritize rest and recovery. If you don’t, it’s like working every single day with no PTO, she says. “Your body needs a really great balance of hard work and recovery.” Your HRV, and overall health and fitness, will be better off for it.
Ultimately, HRV is just one piece of the puzzle. Think of it as a snapshot of how flexible your nervous system is rather than a complete picture of your overall health or fitness. And while a higher one can definitely be a plus, it doesn’t guarantee better performance, longevity, or happiness, especially if you’re ignoring the other healthy habits that also matter.
Related:
- This Is How Much Cardio You Actually Need
- What ‘10,000 Steps a Day’ Gets Right (and Wrong) About Health and Weight
- Here’s What a Balanced and Effective Weekly Workout Plan Actually Looks Like
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