What is HRV?
HRV stands for “Heart Rate Variability,” and is simply the variation between each .
Pulse often gives a basic understanding of your overall heart rate, but HRV goes further by examining the small variations between heartbeats. 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 this is where variation in heartbeats occurs. By understanding how your heart responds to different stimuli and stressors, you gain better insight into your general health and fitness level. Monitoring heart health through HRV can thus be a valuable method to optimize your training and recovery protocols.
Heart rhythm also plays an important role in interpreting HRV data. A regular and stable heart rhythm often indicates the body is balanced and well-recovered, whereas an irregular rhythm can indicate stress or overtraining. Therefore, monitoring both heart rhythm and HRV is crucial for a more complete understanding of one's recovery status, general health, and well-being.
Want to read more about the definition of HRV, you can read more 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 significantly impact your HRV and general health, and it is important to consider this when analyzing your measurements. High stress levels can reduce HRV, indicating your body is under more strain and possibly not fully recovered. Thus, monitoring stress and HRV together provides a more comprehensive understanding of your body's condition.
HRV has been used for many years, but research-wise we are still at a stage where much benefit can be gained from further investigation. So far, it seems:
- Low HRV means you are not fully recovered
- High HRV means you are well recovered
If you follow a program, you might consider whether it is wise to monitor HRV and include it in the assessment of whether the day should involve hard or light training – or perhaps an outright rest day (even if you planned to run). This approach is called “HRV-guided training.”
What HRV Data Can Look Like
Several offer automatic HRV measurements, from which you can get feedback on your recovery status. Below, you can see 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 that this night's sleep was “a step in the right direction.” For context, you can see my HRV history 4 weeks back from this point:
As you can see, there's a period with green dots, which later turn yellow and finally red. Let me explain the context:
Up until August 12, I had a normal training period without “abnormally strenuous” training. On August 13, I went camping and didn’t sleep as well (or as long) as usual. This is clearly seen on the graph, where HRV measurements show lower levels than normal (i.e., worse recovery status).
After the camping trip, I had some very warm nights where sleep wasn’t particularly good, topped off with a hard trail run on August 20 and sore legs the following days.
As the HRV graph shows, my body was slowly getting ready again by the 26th, where I again had HRV within normal levels – yet still with a low average for the last 7 days, suggesting it might be wise to give the body a few more days until the average is within the normal range. Some studies indeed recommend this – read more below.
HRV-Guided Training
A 2021 study used HRV to adjust training recommendations for a group of runners (16 highly trained runners). Simple guidelines were established, evaluated based on a routine with HRV measurement every morning:
- Lower HRV than normal = No high-intensity training, even if on the program
- High HRV = High-intensity training, even if not on the program (max 2 days in a row)
The runners were divided into control and experimental groups, both given the same training plan – but the experimental group adjusted this plan based on HRV measurements, meaning low HRV led to reduced training or rest, while high HRV led to high-intensity training, even if the plan said otherwise.
The result of this experiment was a significant improvement in the fitness level of the experimental group, but no significant improvement in 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 examined HRV training. It finds 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 greater improvement in VO2-max (fitness level) with the inclusion of HRV.
It's worth noting that there are still not many studies on the topic. Results and methods still carry some uncertainty. However, it's not “riskier” than trying it out to see if it works for you.
Summary
HRV shows promising signs, and if you're curious about optimizing your training, it seems you could gain a better outcome from your running training by adding HRV to your dataset.
The approach is simple: First, measure HRV over a period of weeks to find a “baseline” for your variability. Then take note of 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 intense session. If you have high HRV, you might consider whether you have the capacity for an extra session at 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)
