Using Heart Rate Variability to Monitor Your Training

This article was written by Marc Barton, who is a 2nd degree Jiu-Jitsu Black Belt under Mauricio Gomes.  Marc is the head instructor at Kingston Jiu Jitsu and is also a qualified medical doctor. Marc has also contributed articles for a medical education website.

I little while back, I wrote an article on my experiences of overtraining and how I overcame it and took steps to prevent it from happening again. Without a doubt, one of the key measures I have adopted to help me monitor my training and avoid overtraining again has been monitoring my heart rate variability (HRV) on a daily basis.

What is heart rate variability?

A healthy heart does not beat like a metronome, and there are actually subtle fluctuations in the timing between each heartbeat. These slight fluctuations are referred to as heart rate variability (HRV). Even though these fluctuations are very small, and we cannot detect them without specialised devices, they have important implications for our state of well-being and recovery from exercise. They can also be an indicator of current or future health problems.

How does heart rate variability work?

Please bear with me, as I will need to get a little technical to explain this. These fluctuations in the timing between each heartbeat are controlled by the autonomic nervous system (ANS). The ANS is a part of the body's nervous system that regulates body processes such as heart rate, blood pressure and respiratory rate. It also plays a crucial role in body functions such as digestion and sexual activity.

There are two competing branches of the ANS called the sympathetic and parasympathetic nervous systems. The sympathetic nervous system (SNS) regulates the body's 'fight or flight' responses. The actions of the SNS are most apparent when the body is faced with stressful situations. It mobilises energy stores, allowing us to cope and respond to the stress. In contrast, the parasympathetic nervous system (PNS) is responsible for the body's 'rest and digest' and 'feed and breed' activities that occur when the body is at rest.

When you have high HRV, it indicates that your body is well-balanced and is responsive to both sets of inputs (SNS and PNS). This means that your body is in a good state of readiness and capable of performing at its best. In contrast, if your HRV is low, one branch is dominating and sending stronger signals to your heart than the other. Your body is essentially 'out of synch' and incapable of performing at its best.

The conventional wisdom is that the higher your baseline HRV is, the fitter and healthier you are. This is something of a generalisation, though, and HRV is a very personal measurement that has a very wide array of factors that affect it. It is best used by establishing your own baseline and then using this to monitor your training readiness. The more your HRV deviates from its baseline, the less ready it is to be stressed by training. 

Why not just measure your resting heart rate?

So why not just measure your resting heart rate? Surely that will give you enough of a guide of your fitness and readiness to train, and it doesn't require accessing any equipment and is easier to measure?

Unfortunately, this is not true, and while resting heart is a helpful tool in other ways, it is an inferior guide to your training readiness compared to HRV. The resting heart rate is the number of times your heart beats per minute when you are at rest, for example, when you are relaxed, sitting or lying down. The normal range for resting heart rate is 60 to 100 beats per minute. According to the American Heart Association, it's best to measure your RHR first thing in the morning, even before you get out of bed.

A lower resting heart rate is usually a sign of better cardiovascular fitness, but it is affected by numerous factors, such as age, gender, genetics, stress levels and caffeine consumption. In some cases, a low resting heart rate can actually be an indicator that there is a problem with the electrical system of the heart as opposed to a sign of good fitness. At rest, heart rate is an imprecise and inconsistent indicator of your state of readiness and fitness. It definitely cannot compete with HRV as a tool for measuring your readiness for training.

Measuring your heart rate does have a lot of pros, though. It is easy to measure and can be used to target 'zones' while exercising, such as 'fat burning' and 'cardio' zones. It is a fantastic way to measure your level of cardiovascular exertion during exercise in real time and is best used in this way.

HRV, on the other hand, also has some cons. It is not accurate and difficult to measure when exercising, and is best measured at rest. HRV also requires the use of specialised equipment.

In summary, heart rate is most useful when measured during training. In contrast, HRV is most useful when used to monitor your overall health and readiness for training and is best measured in a resting state.

How is heart rate variability measured?

Because the variations in your beat-to-beat heart rate are so small, it requires specialised equipment or devices to detect them. The gold standard is an ECG, but this is not practical outside of healthcare settings. Fortunately, there are a number of great apps available that allow you to measure it with a chest strap or finger monitor, such as Elite HRV and Whoop.

I personally use a chest strap and the Elite HRV app. I find it easy to use, and it only takes a couple of minutes each morning, just after I get out of bed before I eat my breakfast. It doesn't need to be taken completely relaxed like a resting heart rate, but it should be taken roughly the same time each day and in a consistent body position, for example, seated. The app gives me an HRV measurement and a morning readiness score. This allows me to plan my day's training according to my body's ability to cope with it. Since I have been using HRV, I have noticed a massive difference in not only my performance during rolls but also my recovery and general well-being on a day-by-day basis.

As I mentioned earlier, HRV is highly individualised, and you must establish your own baseline pattern over a few days of measurements. Confusingly, different apps use different measurement scales, so you should refer to their population charts to see where you lie compared to others your age.

How can heart rate variability help plan your training?

Here are some examples of readings I have taken recently and how I used them to adjust my training.  

Example 1:

On this day, I was fully rested and feeling great. I was able to do some strength and conditioning work in the morning, as well as teach my classes and have some rolls with a few of my students in the evening. I had no issues performing at my best throughout the day and felt comfortable training.  

Example 2:

This reading was taken a couple of days later. I had continued to push myself on the preceding days and had rolled on two of the previous three days in addition to some kettlebell-based strength work the day before. I woke up feeling a little tired but felt like I had some more in the tank. Before measuring HRV, this was a day where I would have almost certainly continued pushing myself and maybe had a few rolls in the evening. I did not rest completely, however, but instead did a light active recovery workout and went for a family walk. The following day I moved back into the centre of the relative balance graph and was able to return to heavier training safely.

Example 3:

On this day, I had pushed far too hard on the previous 3 or 4 days. My body was sore; I felt tired and fatigued. I try hard to avoid getting into the red part of the graph, but I still have an odd day here and there. I limited my daily activities to stretching and walking. Over the next few days, things gradually improved, and I was able to do some active recovery work.

In summary

Monitoring my HRV daily has been a game-changer for me. Instead of planning my weeks' activities ahead, I am now more flexible in my approach. Overall, since I have started doing it, I feel better and have been able to avoid burning out and overreaching with my training. I highly recommend doing some further reading on it and giving it a go.