Many of us want to perform like an athlete, but we don’t train like one. Athletes know the importance of recovery and varying training intensity. This helps them perform at their best without constantly getting sick or injured.
Heart rate variability (HRV) has been used by elite coaches for more than 20 years to track athletes’ recovery and readiness. Now this technology is available to everyday consumers. Let’s look at what HRV is and how you can use it to train smarter.
What Is Heart Rate Variability?
When your heart is healthy, the time interval between each heartbeat is not consistent. It varies as your body reacts to constant changes like oxygen intake when you inhale and exhale. The variation in time between heartbeats is known as HRV.
A Brief (Non-Boring) History of Heart Rate Variability
In 1965, cardiologists found that right before a person has a heart attack, the variation in time between heartbeats (i.e., HRV) flattens out. It becomes perfectly consistent like the ‘tick-tock’ of a clock.
Fast forward to today and HRV has become an important biomarker for health, fitness, and disease. It’s also made the leap over to the sports world. Elite coaches have been using it for more than 20 years to improve pro- and Olympic-level athletes’ performance.
You no longer need access to a physiology lab or hospital equipment to measure HRV. New technology has made it possible for consumers to track it at home.
How Is Heart Rate Variability Measured?
HRV is commonly measured by an electrocardiogram (ECG) and photoplethysmography (PPG).
If you’ve ever had your heart rate measured by a doctor you may have been hooked up to an ECG machine. ECG machines use adhesive pads (electrodes) attached to your skin to measure electrical activity of your heart. ECG machines are the gold standard for measuring HRV but aren’t convenient for long-term tracking (unless you want to walk around with electrodes and wires hanging off you like one of those hospital crazies).
PPG uses an optical sensor that can be used to detect blood volume changes in tissue. Each time your heart contracts, blood pulses through the arteries towards the small capillaries. Optical sensors reflect light towards blood veins to measure blood volume pulse. These are the sensors most commonly found on wristband wearables like Fitbits and Garmins.
Wearables That Can Measure Heart Rate Variability Accurately
To measure HRV, you need a device that can accurately measure the interval between heartbeats (known as the R-R interval). Many of the popular wearables like Fitbit and Garmin don’t get accurate readings or provide you with raw data (they might give you a stress score instead, for example).
If you’re interested in wearables that can track HRV, here are some good options that have been validated against ECG standards:
What Does Heart Rate Variability Tell Us?
There are two branches that form your autonomic nervous system: parasympathetic (known as rest and digest) and sympathetic (known as fight or flight). HRV is a measurement that tells us that both branches are functioning.
Here’s an image of the two branches of your autonomic nervous system:
We’ve all been in situations where a rush of adrenaline takes over and your survival mechanisms kick in. This is your fight or flight response protecting you from that sketchy stranger or dangerous situation. On the flip side, when you’ve escaped the office and are sitting on the beach sipping mojitos, your rest and digest branch kicks in. In other words, you’re chillaxing.
When you’re in a rest and digest dominant state, your heart rate slows, which means there is more variability between heartbeats. When you’re in a fight or flight dominant state, your heart rate increases, which means there is less room for variability between heartbeats.
By measuring HRV, you get valuable data on your readiness to train hard. It tells you how your body recovers from exercise, stress, and fatigue. It’s a window into your nervous system or the equivalent of the ‘check engine’ light on your car.
What Affects Heart Rate Variability?
HRV is a sensitive metric and can be influenced by a range of internal and external factors like:
- Physiology: age, gender, and circadian rhythm
- Genetics: ethnic origin
- Illnesses: both mental and physical
- Lifestyle habits: physical fitness or sporting activity, increased body weight, smoking, drinking, etc.
- External factors: medications, climate, shift work, noise, etc.
How to Use Heart Rate Variability to Train Smarter
HRV is a good indication of how your nervous system is functioning, but it’s only one metric. If you simply interpret it as high = good and low = bad, you won’t get the full benefits.
HRV needs to be assessed in the context of training intensity, type of activities, lifestyle factors (stress, sleep, nutrition, etc.). When you use HRV to look at your health and fitness from different angles, compare it to other metrics, and pay attention to how you feel, it provides much more insight.
For example, if you’re pushing hard in training, you want your HRV to be lower for a short period. But it should return to baseline or improve when you taper off.
HRV is just one piece of the health and fitness puzzle. But it can provide insights to help you train smarter. Here are some ways you can use it.
Find Your Baseline
This is the most important first step. HRV is a sensitive metric, so taking it as a one-off measure isn’t useful. You need to collect a baseline over at least 30 days. Make sure you take it at the same time and setting—in bed as soon as you wake up works well—every day. Once you have an average you can start to look for patterns.
Focus on Changes from Your Baseline
As a general rule, a higher HRV is better. But this isn’t always the case. Studies have found higher HRV in endurance athletes that are overtrained.
On the other hand, a lower HRV isn’t always bad. For example, you’d expect it to be low during periods of tough training when you’re overreaching. The idea is that you push hard for a short period, then recover. If you’ve done this the right way, your HRV should return to baseline or improve.
The most important thing to measure is changes in HRV from your baseline. Use your general high and general low numbers as an indicator of readiness to train.
Use Heart Rate Variability to Determine Daily Training Intensity
HRV is useful for determining training intensity. For example, if you’ve got a tough workout planned but have a low score, you could do some low to moderate intensity cardio work instead.
A 2007 study tested the idea of using HRV to adjust training on the fly. The study found that men who used HRV to adjust training improved running performance more than the group that followed a pre-planned schedule.
Look for Trends and Compare to Other Metrics
You can look for trends in HRV. If you notice it going up or down, make a note of your activities and see if you can correlate it to anything. You might find that when you don’t sleep well HRV goes down. Or if HRV is going up, maybe your body is adapting to your training. Look for patterns and test assumptions.
The best way to do this is by using an app that tracks other data along with HRV. Some examples of apps and wearables that do this are:
Take Action—Change Your Numbers
If your HRV is low you have the power to change it. That’s the whole point of tracking. You can often bring it closer to your baseline by doing easy activities like yoga or hiking.
Don’t just consume information. If you’ve read this far, I’m assuming you find this post useful. You’ve now got two choices: 1) close the screen and think ‘that’s nice’ and move on with your day. Or 2) if you’ve got a heart rate strap or wearable, start tracking HRV. Start with baseline measurements on waking for 30 days. And as Nike says, just do it! Decision creates action. Action creates results.
I Need Your Help
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You can also share some love by adding a comment below. Let me know if you track HRV and if it’s helped your training.
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