Power vs Heart Rate for Low and High Intensity Training With Dr. Stephen Seiler

Which is a more useful training metric, power or heart rate? Considering the popularity of power training, Dr. Seiler's answer to this question might surprise you. We discuss all the nuance of training with both metrics for both low intensity and high intensity rides.

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[stuartdryer]

As a guy who teaches renal and cardiovascular physiology at a medical school, I totally agree with all of this. So much of it depends on the conditions. A key element is that whenever it is harder for your body to maintain a body temperature in the face of stimuli that want to increase it, then the heart rate will increase for any given power output. This is because the heart is going to have to pump more blood into the skin so that you can radiate heat and that means less is available to power the muscles. It's as simple as that except that that means it's not very simple. The complexity is that there are many environmental factors that tend to make your body temperature increase. Your body will gain heat as a result of convection (how hot it is outside), through radiation (shade or direct sunlight), and through heat generated by muscular exertion and other metabolic activities (your power output). If it's very hot outside you gain more heat through convection (and lose less through breathing). If you're in the direct sunlight, you gain more heat through radiation. If it's very humid outside, the efficiency of sweating as a mechanism to lower your body temperature becomes much less effective. Actually if you are a very fast cyclist then the air moving around you will help with that. I live in Houston so those are the things that mostly are on my mind, but altitude is also an issue. When it's really hot outside, you should rely more on heart rate and RPE because if you don't you could get yourself into trouble; and that is assuming that you are staying on top of hydration and electrolyte input. Obviously your body can heat adapt, but not enough to fully compensate when the temperature is above about 90 and the humidity is high. Before you're fully heat adapted the effect on heart rate is much greater, but no amount of heat adaptation is going to fully eliminate that effect, . Once you are heated adapted the combination of heart rate and RPE is probably the best measures of how hard you are actually working. I'm talking in all of this about pacing a ride, not so much about interval training, which is an element that I know much less about. Although some of the same elements are going to come into play even there.

[jcsrst]

I have been cycling for my entire adult life and now that I am older I've had to back off the intensity. When I was younger I could go out and smash it all the time and recover quickly. Now it takes me days to recover from a high intensity ride. It's been a hard lesson to learn for me. Getting old isn't for sissies 🤣. Now I do a lot more low intensity work using heart rate. This has helped so much! I do one ride a week, usually with others where I hammer the rest is LSD, long, slow, distance with a low heart rate. Everyone is different but this works for me 😊

[joelecho]

I really like how someone who has the level of expertise that Stephen has still has an approach with a fair bit of "you know, if you're more or less doing this, or listening to this feeling, you're on the right track".

Takes a lot of the stress out of trying to get it perfect.

[colinherd]

Back when I swallowed the power pill, and I used to train to power, I was always uneasy about training to an output. It never really felt right. Heart Rate, whatever the conditions is a direct physiological measure of your response to the effort. Power is just the output that your capable of in those conditions. Its only really useful in comparing yourself to others. It’s always struck me as odd to train using a variable output measurement rather than a direct physiological measurement. I can tell you this, after switching back to HR based training, as I get older, I enjoy my training much more and am better at listening to my body, and I don’t overtrain anymore….but I’m just another sad old MAMIL, so what do I know….😊

[justittude]

I now know why im always so so so hungry after low intensity sessions, always wondered why my appetite is so high.

Also learnt that low intensity sessions that go for long durations can turn out to be high intensity without knowing, keep an eye on the heart rate.

[rickheasman]

Listening to Dr Stephen Seiler's talk was both interesting and informative . Great content .

[BLaZEjjp]

11:40 60% of my Heart rate reserve is 88 bpm. This seems crazy low for a low intensity bike ride. Right now my endurance rides seem easy and i can listen to audiobooks if I stick below 140bpm (max 185, resting 38).
edit: I found a similar comment with an answer. Dr Seiler forgot to add back your resting heart rate when he described the process.

[farrier]

I am a 63 year old cyclist-XC skier. I am amazed at how training techniques will come & go according to the flavor of
the moment. Been there done that. I have done away with all the gizmos, I just go by feel, good day-OK day-bad day & adjust accordingly. As the Doc said, listen to your body, perception of your efforts is where it's at !

[dougnevitt]

Man, thank You so much for this. It makes a ton of sense. I realize I have made a lot of training mistakes, burning out quickly, not enjoying riding anymore

[shanelahousse]

Dylan, thank you also for the weightlifting reference, great insight as a strength and power athlete (football) growing up, the stepping up weight then reducing the reps analogy is perfect. I always was thinking there’s something completely different about endurance training than strength but they have very strong correlations.

I’m glad to reconnect with your knowledge pipeline after a long break (literally broke my leg last year and back on the trail for 6 weeks so far this year). You continue to inspire on Strava and educate and entertain online!

[rckd]

Just wanted to say how much I love your content. I'm not the best cyclist but I really like to dig into these types of technical details. Keep on the great work.

[stuartmisfeldt]

As always, you any Dr. Seiler are spot on. I wish there was a little reiteration of HR vs. LT1 and LT 2 for clarification of where drift occurs. I believe he touched on it in his last video, but I know he goes in depth on his channel.

[barmouthbridge]

Temperature too. at cold temperatures your drift may not occur at all until 3 hours in at 200 watts. at 30 degrees C you might start drifting after an hour at 200 watts. so as well as load and measured stress the involvement of external temp will also hugely effect the boundaries shifting.

[adamsims]

I've always found my HR the best indicator of training/fitness. Good to know that my HR based threshold efforts are the best way to start before zeroing in on an actual FTP number. I like to do 2 x 20min @ 176bpm (my max HR is 191).... And let the power fall wherever. Then use those FTP numbers moving forward

[calebkay]

That point on focus versus distraction, and appetite being an indicator of effort, was super insightful!

[seahorserider]

Tried a low intensity ride yesterday (first time pretty much ever) at roughly 60% of my HRmax. Lots of discipline needed cause people were overtaking me left right and center. Seiler talks about that testosterone driven response in situations like these and I can tell you it's hard to resist not to counter. Next time I'll wear a sign "low int ride today" or sthg like that

[seanberce]

Dylan's training plans are awesome, I used them to finish Unbound 200 twice.

[jasonmcgrody]

So on point. Two days after this video, on July 4th, the Giro d'Italia Donne had a very hot day of 35C/95F. American rider and GC contender Kristen Faulkner blew up at the base of climb 3 of 4 because, as she mentioned on Strava, she was dehydrated and setting several personal highs for Heart Rate.

[Bob_Shy_]

I'm glad he mentioned the brain 'zeroing in' on other things when we ask effort from ourseleves. There are things going on in our mammal bodies that we are never aware of. Some things we are, like pain, heart rate and breathing.

[Saoco]

Your heart never stop working. You will know when it does. If you want to target 300w effort. It will come down to if your heart can sustain this effort. Meaning pump the blood needed for this effort. Everything comes down to your heart.