What is Heart Rate Variability? How triathletes can use HRV to optimise their training

0 10 minutes read

What is Heart Rate Variability? How triathletes can use HRV to optimise their training

Heart Rate Variability (HRV) is a data point which is getting more interest. Smart fitness watches and wellbeing-focused wearables have added HRV as one of the many tracking measures in recent years. But what does HRV actually mean, and what can it tell you about how your body is tolerating and adapting to your triathlon training?

While many of us keep a track of our heart rate during training sessions, and even our day to day resting heart rate as a way to build up a picture of our fitness. Heart Rate Variability (HRV) is a slightly newer kid on the block. As with any fitness data, it’s important to understand what it means and how to use it – and to avoid getting overly hung up on it. But once you get to grips with HRV, it can be a useful part of the overall picture to help you balance the constant juggle of risk vs reward, fitness vs fatigue that comes with triathlon training. We caught up with expert endurance coaches in the triathlon and running world to get their take on what HRV means, what we can learn from it and how to use it to guide our training.

Meet the experts

Fran Bungay triathlon coach Goal Specific Training Today

Fran and Ade Bungay – Triathlon Coaches

Fran and Ade Bungay run Goalspecific Coaching which provides 121 coaching for athletes ranging from juniors to those in their 70s and from complete novice to championship gold medalists across all distances. They both set up and coach a non profit making triathlon club in the Purbecks in Dorset. Both Fran and Ade also work for the British Triathlon Federation as Coach Educators on all of the courses including the High Performance Coaching Programme as lead tutors and mentors. Fran is also a Level 7 qualified sports nutritionist, and is a top Age group athlete in 70.3 Triathlon racing. Ade has been in teaching and teacher development for over 30 years, has a PhD in Physics. Together they also work as coach consultants with the team developing the Training Today app for Apple users.

Stephen Fraser – Personal Trainer and Running Coach

Stephen Fraser is the owner of FITT Principle studio, a personal trainer and running coach for over 10 years.
He’s completed marathons all around the world including the Great Wall of China, Polar Circle and 3000m high in the Alps.

What does Heart Rate Variability mean and how is it different to resting heart rate?

HRV is a measure of the variation in time between each consecutive heartbeat. Your resting heart rate tells you how many times your heart beats in one minute. Whereas your heart rate variability tells you how much variability there is in the gap between each heartbeat.

While your heart might beat 60 times in one minute, the time elapsed between each heart beat changes – the gap between consecutive heart beats doesn’t remain the same. Resting heart rate tells you how fast your heart is beating. HRV tells you how much variability there is in the timing of the beats.

So what does HRV actually tell us?

For endurance athletes, looking at trends in our HRV can offer up a useful, holistic snapshot of how our body is responding to the demands of not only our training load. But also all the other stresses and demands outside of training that have an impact on our body’s ability to adapt and recover.

This is because our HRV is actually telling us about our nervous system. Running coach and personal trainer Stephen Fraser explains: “HRV (Heart Rate Variability) offers endurance athletes a glimpse into their body’s recovery and stress levels. It measures the Autonomic Nervous System (ANS) balance between the sympathetic nervous system (SNS), which is responsible for “fight or flight” responses, and the parasympathetic nervous system (PNS), which is responsible for recovery.”

“A higher HRV generally indicates that the body is efficient in managing the training load well, thus recovering better. On the other hand, a lower HRV could suggest that the body is under stress, potentially from overtraining, lack of sleep, or insufficient recovery. Monitoring HRV can help athletes gauge if they’re pushing too hard or if their body needs rest.”

What factors influence Heart Rate Variability?

One of the reasons that HRV can be a useful data point to track is that it takes into account factors beyond just the training sessions you’re ticking off that will all place additional demands on your body. Fitness and fatigue scores in various training apps will be based solely on your uploaded exercise activities. But those scores don’t take into account how, for example, a super stressful day at work or a terrible night of sleep has impacted your nervous system – and therefore your recovery.

So monitoring your HRV can be a way to get a more zoomed out picture of what affect your lifestyle as a whole is having on your body. Triathlon coach Fran Bungay from Goalspecific Coaching, who’s part of the team at Training Today, highlights that: “Parasympathetic activity and hence HRV is suppressed by all types of stress put on an athlete’s body. This could be training stress but it is certainly not limited to that.”

Road cyclist — HRV data gives us an insight into how well we’re managing training load and other lifestyle stress.

“Illness, lack of sleep, work stress, nutrition, alcohol and anxiety for example, are also likely to have a suppressing effect on HRV. Slowing down recovery and potentially reducing the body’s ability to execute training sessions and gain the maximum fitness benefit from doing so.”

Fran recommends that athletes and their coaches need to “take a holistic view of affecting athletic performance.” If your training load is dialled in, but you’re also layering a bunch of emotional stress or an ultra-busy schedule on top of that. It’s likely that those hours outside of training will be having a knock-on impact on your body’s ability to tolerate what would normally be a manageable training load.

Is there such a thing as a ‘good’ HRV score? Why Heart Rate Variability tracking needs a personalised approach

Plenty of us endurance athletes lean towards a Type A personality. We have a habit of almost gamifying our health and fitness stats: we want the best VO2 max, the highest FTP, the ultimate sleep score. And that can lead us to start comparing numbers. But it’s important to understand that a ‘good HRV’ isn’t an arbitrary number. HRV is all about looking at your individual baseline, and tracking trends over time to get a feel for the direction of travel.

“It is important to note that an athlete’s baseline HRV is highly individualised. In other words it is of little value to compare one individual’s HRV with another,” Ade Bungay from Goal Specific/Training Today explains. “It is also well known that baseline HRV declines with age, reducing as you get older.”

“Monitoring the baseline value is a useful indicator of how well your body is responding to training. As an individual’s fitness increases, we typically see a lowering of resting heart rate (RHR) and an associated increase in average HRV. Whilst this does not ‘quantify’ your fitness, it does give a good indicator of the overall direction of travel – i.e. is the exercise you are doing having the desired effect.”

Okay, but surely a high HRV is better than a low HRV – right?

If a higher heart rate variability indicates a balanced nervous system, and therefore a body that is responding well to training stimulus. It’s easy to slip into the trap of believing the higher the HRV score, the better. After all, who doesn’t love a high score? However, there is evidence to suggest that abnormally high HRV values compared to your baseline can still be a signal that you’re overreaching in training – with your parasympathetic nervous system working overtime to try and get things back in balance.

“Over trained athletes may experience chronically low HRV for several days but for other athletes, the opposite may happen and HRV may stay unusually high for several days, essentially they go into a state of hyper recovery,” says Fran. “Neither is good. In fact a good rule of thumb is to say that HRV should vary.”

It’s all about context and comparison with your personal baseline, not someone else’s scores, says Stephen. “Whilst a higher HRV typically suggests better recovery and overall cardiovascular health, we need to look at the data more closely and understand the context. HRV is a very personal thing and our baselines can’t really be compared to someone else. Instead it is more important to understand your own baseline HRV and what trends occur over time.”

How to track Heart Rate Variability

Plenty of smart multisport watches including Garmin and Coros feature a built-in HRV tracking feature. Wear your watch 24/7 and your device will track your HRV alongside other metrics like resting heart rate and in some cases, sleep scores. If your watch doesn’t track HRV and you don’t fancy an upgrade, you can also look at some of the more holistic wearables out there like Whoop and Oura ring.

Lactate threshold testing Loughborough performance lab — Compared to other data measures, like lactate threshold testing which you can see here. HRV tracking is a non-invasive way to get intel on how your body is operating.

Once you’ve got a device to measure your Heart Rate Variability, it’s important to understand that you need to get your individual baseline – a picture of your ‘normal’. And then look at trends in your HRV over time, rather than expecting an instant snapshot. “It is important that the baseline HRV is collected over a significant enough period to flatten out day to day variation, but not so long that age related effects could have a significant impact,” explains Ade.

“Looking for trends is also very useful – a steadily declining HRV indicates a need for more recovery and could indicate a suppressed immune system or onset of illness. An increasing trend, even if the most recent value is a little low, is generally a good sign that you are ready to execute your session.”

How can we use HRV data to optimise our training and recovery?

As age-groupers, we all have a lot of plates to spin: work, family/friends, training to name but a few. And so HRV data can be a useful way to get an objective measure of how well we’re coping with that balancing act. As Ade has highlighted, a balanced HRV with a steadily increasing trend is generally a good sign that you’re managing your overall stress load (training plus everything else) well. Whereas an unbalanced HRV that remains out of range for several days might mean you need to pull back on your training.

“Effective monitoring of HRV can give great insights to help plan appropriate training but it is important that you learn to interpret the data in the context of the individual athletes. Over emphasis on a single reading should be avoided when making decisions which is why many of the tracking apps, including Training Today, take multiple readings of HRV to arrive at a current ‘readiness’ score.”

Remember that HRV isn’t just based on your training

It’s important to remember that your training volume and intensity aren’t the only factors that have an impact on your HRV. You might notice a downward trend in HRV data, but it’s not necessarily just a case of adapting your training – there are other factors to address, too.

“Whilst HRV data can be useful, it normally depicts the end product of all the other factors we are dealing with,” Stephen highlights. “We need to remember that HRV is the relationship between the SNS and PNS nervous systems. If our sleep quality, nutrition, lifestyle stressors are all over the place, adjusting our training might be low down on the priority list to try and fix first.”

Just like HRV gives us a more holistic take on how our bodies are responding and adapting to demands. We also need to take a holistic approach to using our HRV data. If you notice your HRV is remaining unbalanced over several days, don’t just look at your training. Be honest and take a look at everything else – your nutrition, workload, recovery time – to get a better idea of the root cause. It might be that you need to take a couple of extra easier days in training. But if you don’t address other lifestyle factors at the same time, you’ll end up right back in a HRV hole.

Don’t be too dictated by data

Like with all training data, it’s important to remember that you’re not a robot. Just because the objective data says you can push hard in training on any given day – it doesn’t necessarily mean that you should, or that you have to.

“There’s a risk of becoming overly focused on data, which might overshadow important subjective aspects like the athlete’s mood, or how they perceive their body condition on that given day,” says Stephen.

“Using HRV and other data metrics as guides rather than strict rules is the way forward. Data is good at spotting trends over time but there might be the outlier day where we go against the grain, and that’s ok!”

How to balance HRV

If you’re noticing a significant trend – lower or higher than your baseline – over several days. It’s important to take a beat to understand what factors might be influencing your HRV. Have you increased your training load significantly? Have you had work deadlines or stressful events at home? Stress, fatigue and the onset of illness can all have an impact on your HRV balance.

How to improve sleep for sports performance — Rest, recovery and good sleep are all key for a balanced HRV.

Alongside addressing any obvious factors, you can help to calm your nervous system by prioritising rest and recovery between training sessions. Getting good quality sleep. Focusing on balanced nutrition that fuels your training properly. And where possible, reducing stress – as tricky as that can be!

The bottom line on HRV

Unlike metrics such as resting heart rate and VO2 max which are predominantly giving you an indication of how efficiently your cardiovascular system is working (i.e. fitness). Heart Rate Variability is a data point which indicates the balance of your nervous system. Therefore giving you an idea of how well, overall, your body is managing the demands of your training alongside all your other daily stresses and activity.

By tracking your HRV over time, you can start to pin point any lifestyle factors that are impacting your recovery and therefore how effectively your body will be able to adapt to training and progress. And you can also see it as an early warning system to understand when you need to pull back a little and prioritise rest, to avoid burn out.

Looking for more training tips and data demystifiers? You might enjoy these articles: