Coach Tom Craggs explains how he uses Heart Rate Variability (HRV)

In the past I have written about the importance of being adaptive in the way we plan. A direction, a focus on the demands of the event and what we are trying to achieve is critical. For me though the detail should be iterative and stem out of self reflection and feedback with ourselves, a coach, a mentor, other athletes and other sports professionals where relevant.

But being adaptive isn’t just about be reactive – responding to a niggle, a tired run, a new PB. It’s more about being proactive – interpreting a wide range of data (and not just biophysical data) and conversations to tweak and tinker. Treating training in this way is more like painting a picture as Dr Andrew Kirkland once said to me, not following a road map.

In order to do this well performance analysis becomes a much more central part of the coaching/self coaching process. This goes beyond just looking at GPS splits from a run or heart rate data from a session. How an athlete feels around their training is probably more critical.

Some time ago the brilliant and humble Rob Griffiths chatted to me about the benefits he has seen monitoring Heart Rate Variability (HRV) with the athletes he coaches. I started to include it a bit more in my coaching process and have found it to be very useful.

What is HRV?

Heart Rate Variability (HRV) is a measurement of the variation in time between each heart beat, your R-R interval, and it is controlled by your autonomic nervous system (ANS). It is different from your heart rate which is a measurement of the number of times your heart beats over a given time span (usually one minute).

Your ANS plays a key role in regulating your respiratory rate, pupillary response, digestive system and even your sexual arousal amongst other things and it is composed of the sympathetic nervous system and parasympathetic nervous system. These two systems can be over simplified as your ‘fight or flight’ response and your ‘dampening’ or ‘resting’ response. HRV is a way of quantifying/measuring the activity of the vagus nerve.

How can it be used?

HRV can be used as a method of monitoring changes in your autonomic nervous system. In essence it is a method of assessing your state of stress. Generally the greater your HRV the better you are recovering and the more receptive you will be to further training stress.

It can help tell us whether an athlete’s training load is appropriate, whether they might be at risk of colds or infections in the near future. As athletes we are often not very good at knowing when to push and when to back off. The warning signs aren’t always obvious and sometimes we prefer to see evidence before we adapt.

If we want to perform we need to ask ourselves “am I recovering well?”, “is my training load about right?”, “am I receptive to hard sessions?” “will this training make me fitter?”. HRV gives us a littler extra help answering these questions. Some athletes after all are pretty damn good at tolerating or normalising pain and discomfort.

How is it measured?

The gold standard for measurement is an electrocardiogram. In the real world runners or coaches will be using either a wearable device with an HR strap or using their phone with an app which can record HRV using photoplethysmography.

Apps such as HRV4Training and EliteHRV are just two of many examples and have free versions which are suitable for most.

Validity and reliability

Any set of data is only as good as the validity and reliability of the system used to collect it. Before deciding how you want to measure it be sure to do some research into whether the data you’ll be seeing is something meaningful. Different devices and different methods of collecting HRV data will have different levels of accuracy. There are countless studies you can read – for example this on the validity of smartphone HRV measurement.

Regardless of the accuracy of the tool sometimes I just don’t get consistently good, reliable data which tells me anything useful about performance and training. This could be due to ‘user error’ (see below) or just recognising that, regardless of the published research, the n=1 rule applies to all of us!

So of course beyond the device itself is the athlete. The number of times I have had a runner tell me their watch does not collect HR readings accurately whilst having their watch or HR strap positioned incorrectly. So take time to read and follow a consistent protocol suited tot he device you are using.

Data will be affected by the time of day and frequency of recordings and of course by your training and recovery (thats the point!). Also by other factors including nutrition, hydration, whether you’ve just eaten, whether you’ve just necked a few espressos. This doesn’t mean the data is useless, just that we need to understand the context of the data, its limitations and search for some consistent protocols in recording.

Education is required on what the data means and how to use it. Recording data for recording sake, or even worse using inaccurate or unreliable data is unhelpful. As this article from former UKA Performance Director Dave Collins states, the ‘what’, ‘how’ and ‘why’ need to be understood.

How HRV helps adaptive planning

As mentioned at the start is that HRV is another (small) piece in the puzzle of making training as proactive as possible. The image below shows screenshot of data from an HRV app (HRV4Training in this case). This particular app gives ‘recovery points’ as a proxy for an HRV reading but it’s the same idea.

You can see the decrease in HRV in the track of the blue line. The colours at the bottom indicate how hard the athletes training is. Measuring HRV has allowed for changes to be made to training reducing intensity for a period of days and only reintroducing harder sessions when a baseline has been met.

What’s the point?

What’s the point of all this? Acceptance that beyond any quality session or extra mileage the thing that gets us fit above all is is consistency. Being proactive and adapting training in response to warning signs of overtraining/under recovery or illness we can increase consistency.

By adapting training early we might be able to support your body to fight off an infection (by not adding further hard training stress). Or prevent an injury (by not hitting high intensities during periods when your body is most susceptible to injury). It can also help inform, as per below, when an athlete is ready to tackle a harder session again after a cold or infection.

A niggle or infection in a key competition cycle can make or break the end result. HRV is just another tool we have available as an athlete or coach inform training. Beyond training it can be a prompt to focus on things that promote recovery – good sleep, lower psychological stress, good nutrition. We can check the impact of our harder sessions or a change in stimulus (such as an increase in mileage, change in pattern of rest days etc).


Self reflection the most useful tool

Not everyone I coach wants record HRV, that’s fine. Some record it and don’t share the data with me (via Training Peaks). This is also fine. One of the main benefits of encouraging athletes to use an app to record HRV is that it stimulates self reflection. That is more important than me as a coach having a load of data.

Most of the apps available will not only be recording HRV but will also ask a range of other questions around recovery. ‘How did you sleep last night?’, ‘what are your energy levels like?’, ‘how sore are your muscles?’, ‘how motivated are you to train?’. Of course as a coach I want to know these things too but more importantly Id rather an athlete ask first. Whilst we all know this day to day ‘listening to our body’ is important, we don’t always do it.

No data is a substitute for conversations

I saw a tweet recently from Dr Stephen Seiler that got me thinking;

The answers to this question are interesting to read and quite telling. We love to measure and quantify. It makes its feel in control.

This is another area of the ‘art vs science’ of coaching debate. Like always though it’s doesn’t need to be one or the other. The better a coach gets to know an athlete they can pick up on other subtle cues. Tone of voice, the ‘zip’ of an athlete’s strides or drills, how positive an athlete is about sessions.

No app, watch, lab test or algorithm will ever be more important than a conversation a coach has with an athlete, or an athlete has with themselves.

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