There's more in life than training: non-training related stressors and recovery

Blog post by Marco Altini

One of my favorite guest posts on our blog was written a few years back by Andrew Flatt. Andrew is a brilliant scientist and coach and has dedicated much of his time to investigating the relationships between HRV, training load and other stressors, in a variety of sports and athletes.

The full article focuses mostly on strength and power athletes, and can be found here. However, I believe some aspects are really applicable to any sport, and I'd like to report them here and show a little example using my own data collected with HRV4Training and the Pro platform.

Quoting Andrew:

"Highly trained individuals are more likely to see a pronounced decrease in HRV the following morning in response to a training session if: 

1. The training stimulus is considerably greater than the individual typically experiences (an abrupt increase in load

2. The training stimulus is novel or different from what the individual is accustomed

3. Training is otherwise normal, but non-training related stressors are affecting recovery" 

Point 3 is the one I'd really like to focus on in this post. Non-training related stressors are key. There's a whole body of research looking for example and how injury risk can increase due to high stress regardless of any changes in training, see psychophysiological models of injury for example. Needless to say, our capacity to handle stress is limited, and this exactly why HRV measurements are useful: they provide an overall marker of stress

In my view, non-training related stressors are an often overlooked great reason to use HRV monitoring, despite the fact we all understand well that if something is bothering us (issues at work, at home, financial concerns, etc) we can hardly focus and perform optimally.

As a recreational runner, I love to try to make a bit of progress, pushing myself to higher loads from time to time. When I manage to do so gradually and consistently, over longer periods of time ( > than a year for example), I do not expect my HRV to drop during an acute high-load block, as my body is well conditioned, and should assimilate the stimulus properly.

When we add other stressors though, the situation can easily change, and this is exactly why it is important to objectively monitor physiological stress and individual responses to stress (in a generic way), so that we can get the full picture. It would be really naive to think that the only thing that matters is training, and all we do in the remaining 22-23 hours of our day is irrelevant.

​Lets look at some data:

Above we can see three plots, with daily measurements collected over 3 months, first thing in the morning using the HRV4Training app:

• Physiological data (heart rate variability). Here is how we show historical data or normal values (light blue band), baseline (blue thick line) and daily scores (light gray bars) to make it easier to look at the big picture in HRV4Training Pro. You can find more information about how to use this visualization, here. 
• Training load: in this case I am using running distance, and showing a period of high load (in orange we have the acute load, and in blue the chronic load, when the acute load is higher than the chronic, it means that on a given week we are loading more than we are normally used to). We can also see how HRV data looks really good during this period of load, with the baseline increasing over time (anything that is an increase or a stable baseline during a high load period is typically a good sign, positive adaptation)
• Subjective data: in the last plot I annotate my "lifestyle stress" subjectively, based on how stressful my days have been. Note that we always advocate integrating these three aspects (physiological data, training load and subjective data) so that you have the full picture for yourself or your athletes, and can improve the decision making process. Here we can see how work stress increases quite a bit in the last period, while it was very low earlier. As stress increases, my HRV drops (the same situation can actually be seen at the beginning of the three months). We have recently added normal values to the subjective data as well, to make it easier to spot significant trends, and not only normal day to day variations.

We can also look at the correlation between physiological data and subjective metrics, in the Explore Correlations page that you can find under Insights in HRV4Training Pro:

In the plot above we can see again the strong baseline correlation between heart rate variability measured first thing in the morning, and lifestyle stress. As you can see "work stress" for me is typically the largest factor behind drops in HRV, especially when looking at the big picture (baseline more than day to day correlations).

Alright, hopefully this post gives you a more practical view of what to expect and how to interpret the data, always remember that multiple stressors play a role at the same time, and it is therefore beneficial to look at the data over longer periods of time, including normal values and baseline changes, and contextualizing physiological data (HRV or HR) with respect to your subjective annotations and training load. This is all computed for you in HRV4Training Pro.

take care!

Marco Altini

​​Founder of HRV4Training 

PhD in Data Science, MSc (2x) in Computer Science Engineering, Sport Science. 

Twitter: @altini_marco