I have received this question a few times since Suunto released their new feature using HRV (and detrended fluctuation analysis, or DFA) to determine exercise intensity, hence this blog post.
fantastic insight, absolutely love it. I would've 100% fallen for the marketing. This helps tremendously to better understand the areas (e.g. DFA) where I am not knowledgable enough to critique the estimates properly. Thank you! The chain is only as strong as its weakest link. Still following
Very interesting thoughts here. Objective and thorough.
I've been using the ZoneSense for a few runs now and find the data interesting. As a hrv4training user for a number of years now I tend to rely on that app as my "go to" for how I train on a particular day. It's been great, particularly with the large number of metrics available (good work! :-) ) ZoneSense (ZS) is another way to look at my running I guess, in real time, and how my HRV is variously moving from aerobic/anaerobic etc.
However I have found that in some instances, running up hills, and thus generating a high heart rate has ZS still in the aerobic zone and not as I would have thought into anaerobic. Any thoughts on why this would be the case?
thank you Jeff, much appreciated! Regarding the issue you mention, I think it could either be an artifact (DFA is sensitive to a few things, even just changing breathing pattern) or simply a problem linked to e.g. the duration of the change in effort (which might be too short for the math to catch up). I would not take it as a sign that you are not working hard :) (especially considering you report a higher heart rate).
Jist of it is not everyone is going to be at 0.75. You take your number from early in the ramp and the mid point from that and 0.5 is a good indicator for intensity. I myself train at 1-1.1 dfa a1. I also find it pretty amazing for detecting fatigue - you notice suppressions immediately on a ramp warm/up even when hrv4training protocol HRV hasn't detected anything. That way you can either lower intensity or shorten duration or both.
PS - AlphaHRV on Garmin is free - the author has some forthcoming papers on it and the same app is going to be used with a continuos lactate monitor that's releasing soon. So soon we'll truly know if dfa lines up with lactate! https://x.com/inigo_tolosa_12/status/1848455884126433441
thanks Dush, I’m glad Rogers eventually came to his senses :)
regarding lactate, I think (and Thomas would agree) that this whole story is pointless: we are looking at cardiac activity, and not metabolic activity. Everything is correlated (heart rate, HRV, blood pressure, lactate, intensity, etc.) but this doesn’t mean that one should be a proxy for the other, unless re-calibrated every few weeks. As I mention in the blog, the interesting part is how lactate and heart rate (or HRV) change in different ways based on how we train (and detrain), and therefore it is meaningless to use one to guess the other (how would I know that my heart rate at LT1 is now higher, if I wasn’t measuring both my heart rate and lactate? - rhetorical question). If HRV during exercises, tuned to your individual thresholds, helps you manage load / fatigue, that’s great, but that’s all there is, it’s not a marker of metabolic thresholds as lactate, which is also fine, just a different way to look at various aspects that relate to fatigue and performance.
100% agree - for me it's an autonomic load tool. "How far can I push my autonomic system today", "how much training does my autonomic system let me do today".
Btw - after using hrv4training for a number of months it finally gave me the confidence to ditch wearing my Garmin continuously & stopping relying on all day stress/overnight HRV. My mind is much freer & I'm not so obsessed with the metrics. I moved to the AW Ultra 2 which I like because of the ability to do morning measurement with hrv4training & the vitals app which answers the simple question "Am I brewing an illness that I can't feel, so should I take it easy today?". Much easier than trying to read the tea leaves with all of Garmins metrics.
This is awesome - thank you! I've been reading about DFA from AI Endurance, who seem to have similar perspectives to you :)
fantastic insight, absolutely love it. I would've 100% fallen for the marketing. This helps tremendously to better understand the areas (e.g. DFA) where I am not knowledgable enough to critique the estimates properly. Thank you! The chain is only as strong as its weakest link. Still following
Hi Marco,
Very interesting thoughts here. Objective and thorough.
I've been using the ZoneSense for a few runs now and find the data interesting. As a hrv4training user for a number of years now I tend to rely on that app as my "go to" for how I train on a particular day. It's been great, particularly with the large number of metrics available (good work! :-) ) ZoneSense (ZS) is another way to look at my running I guess, in real time, and how my HRV is variously moving from aerobic/anaerobic etc.
However I have found that in some instances, running up hills, and thus generating a high heart rate has ZS still in the aerobic zone and not as I would have thought into anaerobic. Any thoughts on why this would be the case?
Regards,
Jeff
thank you Jeff, much appreciated! Regarding the issue you mention, I think it could either be an artifact (DFA is sensitive to a few things, even just changing breathing pattern) or simply a problem linked to e.g. the duration of the change in effort (which might be too short for the math to catch up). I would not take it as a sign that you are not working hard :) (especially considering you report a higher heart rate).
Marco have you seen Bruce Rogers team's latest paper? It's about customising the DFA a1 thresholds. http://www.muscleoxygentraining.com/2024/09/improving-hrvt1-agreement-ijspp-102024.html
Jist of it is not everyone is going to be at 0.75. You take your number from early in the ramp and the mid point from that and 0.5 is a good indicator for intensity. I myself train at 1-1.1 dfa a1. I also find it pretty amazing for detecting fatigue - you notice suppressions immediately on a ramp warm/up even when hrv4training protocol HRV hasn't detected anything. That way you can either lower intensity or shorten duration or both.
PS - AlphaHRV on Garmin is free - the author has some forthcoming papers on it and the same app is going to be used with a continuos lactate monitor that's releasing soon. So soon we'll truly know if dfa lines up with lactate! https://x.com/inigo_tolosa_12/status/1848455884126433441
thanks Dush, I’m glad Rogers eventually came to his senses :)
regarding lactate, I think (and Thomas would agree) that this whole story is pointless: we are looking at cardiac activity, and not metabolic activity. Everything is correlated (heart rate, HRV, blood pressure, lactate, intensity, etc.) but this doesn’t mean that one should be a proxy for the other, unless re-calibrated every few weeks. As I mention in the blog, the interesting part is how lactate and heart rate (or HRV) change in different ways based on how we train (and detrain), and therefore it is meaningless to use one to guess the other (how would I know that my heart rate at LT1 is now higher, if I wasn’t measuring both my heart rate and lactate? - rhetorical question). If HRV during exercises, tuned to your individual thresholds, helps you manage load / fatigue, that’s great, but that’s all there is, it’s not a marker of metabolic thresholds as lactate, which is also fine, just a different way to look at various aspects that relate to fatigue and performance.
100% agree - for me it's an autonomic load tool. "How far can I push my autonomic system today", "how much training does my autonomic system let me do today".
Btw - after using hrv4training for a number of months it finally gave me the confidence to ditch wearing my Garmin continuously & stopping relying on all day stress/overnight HRV. My mind is much freer & I'm not so obsessed with the metrics. I moved to the AW Ultra 2 which I like because of the ability to do morning measurement with hrv4training & the vitals app which answers the simple question "Am I brewing an illness that I can't feel, so should I take it easy today?". Much easier than trying to read the tea leaves with all of Garmins metrics.
thank you so much Dush, I am really glad to read this 🙏