DFA a1 threshold in a cardiac population

Although it has been released in abstract form, our full article describing the use of DFA a1 in a cardiac disease population (CHF and stable CAD) has been published.  As I have done in prior publications, I wanted to share some individual participant data to show how things work "under the hood".  Many thanks to my co authors, Laurent Mourot and Thomas Gronwald.  

We found three important findings - 

• DFA a1 can be used in this very different population to determine the first threshold (VT1).  
• Beta blockade did not appear to affect the index (as discussed here before).
• The improvement in VT1 after cardiac rehab was correlated with that of the improvement in the HRVT.  Therefore, this is the first evidence published showing a1 can be used for following VT1 related fitness status.

How did these parameters look in a single subject?  Here is one example of a participant with CHF, pre and post rehab exercise (Please read the full article for details and background).

Gas Exchange Pre (baseline)

We are using the excess CO2 method (see the article for references).  I did add HR to the plot.

• We can see at about 300 sec into the test, the curve slope changes, at a HR of 76 bpm.  That is the point of the VT1 HR.
  

 

The Pre Rehab HRVT:

DFA a1 vs HR:

• The HR at HRVT is 75 bpm (very close to gas exchange - but not all participants were this close).

Post Rehab Results:

Gas Exchange Post:

And HRVT:

• Both VT1 gas HR and HRVT HR are about the same (81-82).  
• VT1 gas HR improved after rehab as did HRVT HR.

 

We presented this Figure in the article showing the individual responses (ml/kg/min, HR, watt change):

This indicates that those who had improvement in VT1 also had better HRVT metrics.  Those who did not improve with gas exchange generally did not do so with HRV either.

Summary:

• The HRVT concept holds in a markedly different demographic of participants (CAD, CHF), most of whom were on beta blockade therapy.
• Improvement (or not) in first threshold gas exchange parameters was well correlated to that of the change in HRVT related metrics.  
• I hope more groups consider using "correlation properties of HRV", AKA DFA a1 derived HRVT as a fitness metric to follow over time.
  

 

Heart rate variability during dynamic exercise

• Firstbeat VO2 estimation - valid or voodoo? 
• Heart rate variability during exercise - threshold testing
• Exercise in the heat and VO2 max estimation
• DFA alpha1, HRV complexity and polarized training 
• HRV artifact avoidance vs correction, getting it right the first time 
• VT1 correlation to HRV indexes - revisited 
• DFA a1 and Zone 1 limits - the effect of Kubios artifact correction 
• HRV artifact effects on DFA a1 using alternate software  
• A just published article on DFA a1 and Zone 1 demarcation 
• DFA a1 vs intensity metrics via ramp vs constant power intervals 
• DFA a1 decline with intensity, effect of elevated skin temperature 
• Fractal Correlation Properties of Heart Rate Variability (DFA a1): A New Biomarker for Intensity Distribution in Endurance Exercise 
• Movesense Medical ECG V2.0 Firmware brief review 
• Movesense Medical ECG - improving the waveform and HRV accuracy 
• DFA a1 and the aerobic threshold, video conference presentation  
• DFA a1 - running ramp and sample rate observations with the Movesense ECG 
• DFA a1 calculation - Kubios vs Python mini validation
• Frontiers in Physiology - Validation of DFA a1 as a marker of VT1 
• Real time Aerobic thresholds and polarized training with HRV Logger   
• Active Recovery with HRV Logger 
• DFA a1 and exercise intensity FAQ 
• DFA a1 agreement using Polar H10, ECG, HRV logger  
• DFA a1 post HIT, and as marker of fatigue 
• DFA a1 stability over longer exercise times 
• DFA a1, Sample rates and Device quirks 
• DFA a1 and the HRVT2 - VT2/LT2  
• Low DFA a1 while running - a possible fix? 
• Runalyze vs Kubios DFA a1 agreement  
• DFA a1 - Runalyze vs Kubios vs Logger results in a cyclist 
• Best practices for Runalyze and DFA a1 thresholds 
• ACSM - HRVT validation in a cardiac disease population 
• FatMaxxer - a new app for real time a1  
• Another look at indoor exercise without a fan 
• ECG artifact strips from Fatmaxxer - a guide 
• ECG arrhythmia and artifact visualization tips 
• DFA a1 as a marker of endurance exercise fatigue 
• To train hard or not, that's the question 
• DFA a1 HRVT and Ramp slope 
• DFA a1 and optimal HRM belt position