Decreased Heat rate = improved performance?! Beware of the shortcut (PART 2/2).

Continuation of the article “Decrease in HR at a given intensity = improvement in efficiency?! Beware of the shortcut” where we could see that a decrease in Heart Rate (HR) at a given intensity is not necessarily correlated with an improvement in the athlete’s performance or his fitness level.

It has been learned that it is important to have a holistic approach to studying the cardiac response using the dynamic link between exercise (HRexe), rest (HRR), exercise intensity, perception of effort difficulty, perceived fatigue level and training load or even the stress generated on a daily basis (professional, personal).

To go a little further on the study of the cardiac response in the training process, we are also hearing about the analysis of cardiac variability (HRV) as an effective tool to improve training follow-up to adapt individual load, optimize progression and prevent the risks of overreaching/overtraining. Heart rate variability (HRV) is the perpetual fluctuation of the heart rate around its mean heart rate. Its study allows a non-invasive measurement of the autonomic nervous system (ANS).

Why is it important to analyze the NLS?
The balance of the ANS allows the maintenance of the body’s homeostasis (balance of the different constants of the organism). Chronic training will lead to an imbalance in the ANS. If the training load is well managed the organism will adapt positively and improve. Conversely, if the training is excessive or (especially) poorly conducted, it will cause a disturbance of the ANS and consequently a poor adaptation of the organism. Indeed, too much volume or a poorly managed intensity distribution will not necessarily lead to a stronger progression but will most certainly expose the athlete to increased fatigue, a negative adaptation of the organism and a risk of overreaching/overtraining. It may therefore be interesting to use the NLS response within the training process as an indicator of the body’s ability to adapt to exercise stress.

Beware of the shortcut again

The HRV longitudinal analysis is an interesting indicator for studying the adaptation of the organism to the chronic training load or the prevention of fatigue states, but as with the image of the cardiac response during exercise, it should not be the only control used, otherwise the conclusions drawn from the various HRV indices could prove to be false. Once again, it is the global approach that must take precedence, using the dynamic link uniting the various variables: exercise CF, recovery CF, Perception of effort, state of fatigue, load level and lastly the HRV analysis.

Fit, athletic woman wearing a sports bra and heart rate monitor checking her pulse during a training run

What criteria should be taken into account to avoid making mistakes and improve load monitoring in endurance athletes?

A meta-analysis by Bellenger & al (2016) gives us interesting answers on the subject. The purpose of this study was to identify the positive (performance improvement) and negative (lower performance) adaptations generated by the monitoring of training in endurance sports on CF regulation that is under the control of the ANS.They showed that autonomous regulation of the CF, HRV analysis and post-exercise recovery are interesting indicators to study the adaptation of the organism to endurance training stimuli.

The increase in the following indices may indicate a positive adaptation of the body as a result of an endurance training process:

Slight increase in RMSSD[temporal marker representing parasympathetic activity of the autonomic nervous system], high frequency power (HFP)[reflects parasympathetic activity of the autonomic nervous system] and SD1[mainly represents the parasympathetic activity of an individual] at rest.
Moderate increase in RMSSD, SD1 and HR post-exercise
A sharp increase in HR acceleration
At the same time, they were also able to show a decrease in athlete performance by using the following indices:

A slight increase in resting RMSSD
Insignificant change in HFP and SD1 at rest
Increase in post-exercise RMSSD and HFP
Increase in post-exercise HRR
Decreased post-exercise CF acceleration
It is clear that it is not easy to analyse the data and draw conclusions from it. On the one hand the increase in vagal indices (study of the parasympathetic nervous system) at rest and post-exercise are evident when the body positively assimilates the training load by allowing an improvement of the perfo