What is HRV?
HRV stands for “Heart Rate Variability” and, in short, it's the variation between each .
Pulse often provides a basic understanding of your general heart rate, but HRV goes a step further by examining the small variations between beats. This precision allows for a more detailed picture of your body's stress levels and recovery ability. helps with this overview.
Your heart plays a central role in measuring HRV, as it's where the variation in heartbeats arises. By understanding how your heart responds to different stimuli and stressors, you can gain better insight into your overall health and fitness level. Monitoring heart health through HRV can therefore be a valuable method for optimizing your training and recovery protocols.
Heart rhythm also plays an important role in interpreting HRV data. A regular and stable heart rhythm often indicates that the body is balanced and well-recovered, while irregular heart rhythm can be an indicator of stress or overtraining. Therefore, it is important to monitor both heart rhythm and HRV for a more complete understanding of recovery status, general health, and well-being.
If you want to read more about the definition of HRV, you can read further in this article or find others in our inspiration universe.
Training Readiness and HRV
HRV is used as an indicator of how ready your body is for training.
Stress can have a significant impact on your HRV and general health, and it's important to consider this when analyzing your measurements. High levels of stress can reduce HRV, indicating that your body is under greater strain and possibly not fully recovered. Therefore, monitoring stress and HRV together can provide a more holistic understanding of your body's condition.
HRV has been used for many years, but research-wise we are still at a stage where more studies could be beneficial. So far, it appears that:
- Low HRV means you're not fully recovered
- High HRV means you're well-recovered
If you follow a program, you might ask yourself whether it's smart to keep an eye on HRV and consider it when determining if the day should involve hard or light training – or maybe even a rest day (even if you had planned to run). This approach is called “HRV-guided training”.
How HRV Data Can Look
Several of offer automatic HRV measurements, from which you can get feedback on your recovery status. Below is one of my measurements, clipped from Garmin Connect.
The measurements are taken automatically overnight with my Garmin Forerunner 955.
The image shows that my HRV average this week is lower than my normal level, but last night's sleep was “a step in the right direction”. To provide context, here is my HRV history 4 weeks back from this point:
As you can see, there is a period of green dots, which later turn yellow and eventually red. Let me explain the context:
Up until August 12th, I had a normal training period without “abnormally strenuous” training. On August 13th, I went camping and didn’t sleep as well (or as long) as usual. This shows clearly on the graph, where HRV measurements show lower levels than normal (indicating poorer recovery status).
After camping, I had some very warm nights where sleep wasn't particularly good, and this was then topped with a hard trail run on August 20th and sore legs in the following days.
As the HRV graph shows, my body was getting ready again by the 26th, where I again had HRV within the normal range – though still with a low average for the last 7 days, suggesting it might be a good idea to give the body a bit more rest until the average is within the normal range. At least some studies recommend this – read more below.
HRV-Guided Training
A 2021 study used HRV to adjust training recommendations for a group of runners (16 very well-trained runners). Simple guidelines were set based on a routine with HRV measurement every morning:
- Lower HRV than normal = No high-intensity training, even if it's in the schedule
- High HRV = High-intensity training, even if it's not in the schedule (max 2 days in a row)
The runners were divided into a control group and an experimental group, and both received the same training plan – but the experimental group was set to adjust this plan based on HRV measurements, so low HRV meant reduced training or rest, and high HRV meant high-intensity training, even if the plan said otherwise.
The result of this experiment was a significant improvement in VO2 max for the experimental group, and at the same time no significant improvement for the control group. It is also mentioned that everyone in the experimental group set a personal record at the subsequent championship, while only 75% in the control group succeeded in this.
Another review study from 2020 also looked closer at HRV training. It found the same conclusion – namely that using HRV in training planning seems to improve outcomes for endurance athletes – including runners. It particularly appears that one can achieve a greater improvement in VO2 max with the inclusion of HRV.
However, it's worth mentioning that there are still not many studies on the subject. Results and methods are still associated with some uncertainty. However, it's not “riskier” than trying it out to see if it works for you.
Summary
HRV shows promising trends, and if you're curious about optimizing your training, it seems likely you can get better results from your running training by adding HRV to your data set.
The approach is simple: First, measure HRV over several weeks to find a “baseline” for your variability. Then note whether your daily HRV measurement (which should be taken in the morning) is above or below your average.
If your daily HRV measurement is significantly below your baseline, consider whether you might need an extra rest day before the hard session. If you have high HRV, then consider whether you might have the capacity for an extra session with higher intensity.
References
- Bahenský P, Grosicki GJ. Superior Adaptations in Adolescent Runners Using Heart Rate Variability (HRV)-Guided Training at Altitude (2021)
- Granero-Gallegos A, González-Quílez A, Plews D, Carrasco-Poyatos M. HRV-Based Training for Improving VO2max in Endurance Athletes. A Systematic Review with Meta-Analysis (2020)
