Misunderstood Science of Running with Heart Rate

[@NomadicNine]

Best video I've watched on the application of heart rate. Answered the key question in the video and comments on what to do when cardiac drift takes you towards Z3. Thank you!

[@drwilloconnor]

Glad it was helpful!

[@laurenm9997]

Thanks for this! I have been wondering about this as a new runner trying to build up my aerobic capacity with zone 2 training. So glad I came across your video!!

[@drwilloconnor]

Glad it was helpful!

[@danielj347]

Really informative! I've watched a lot of videos the last few years but vo2 slow is a first. Thanks

[@drwilloconnor]

Glad it helped. Cheers.

[@wk633]

That last bit about not using HR for intervals- I need to do that. I really have trouble getting my heart into the intended zone before the 800m or 1200m or whatever is over and my effort ends up all over the place. I know the effort- I need to just trust that. I have another HR question- I'm 57 and come from a cycling background so I'm used to doing hill repeats to get max HR. In my early 40s it was about 180. Fast forward to more recently, and after a few years of no intense activity, and then a year of easing back into running I decided to do another max HR test, and hill repeats running I was only able to hit 150. That's rested, warmed up, with a chest strap. Seems a bit low but everyone's different. It also fits in with what I can maintain over 10-13 miles which is about 137 bpm. But the weird thing is that when I do an initial super easy zone 2 could recite a novel, so slow if I slowed any more I'd be walking warmup, my HR often goes into the mid 150s. It eventually comes down after up to 30 min and I can run steady (5:30-6:00/km) as low as < 110bpm. But I can't figure out why my initial super easy warmup effort results in a HR I can't nearly match when I'm doing VO2Max efforts after warming up.

[@drwilloconnor]

Thanks for your comment and question. Unfortunately, I don't have an answer. What you're describing sounds very confusing. I would test with and without the HR strap as well as a different watch if you were able to borrow one. It sounds more like a technological error than a physiological error.

[@hikerJohn]

I mostly hike and trail run and I also do some biking but I cannot get my HR up to over 165 on a bike but I can get it up to 185 just walking up a long steep hill with a 20% grade (350' in 1/3 mile).

[@prj259]

I find your videos extremely helpful!! Thank you so much for sharing

[@drwilloconnor]

I appreciate you letting me know!

[@nickdalfarra3887]

Thanks for another banger video. I appreciate you making your expertise so widely accessible, you've helped me a lot with my training. This was also the first I'd heart of VO2 slow component, which surprised me because it seems so essential! I'm looking to really understand cardiac drift phenomenon. Here's what I took away from your description: Flow rate = stroke volume x heart rate As you heat up, two things happen 1. more blood flows to your skin, increasing the temperature differential between skin and air 2. you sweat more My questions: - How is sweating more connected to cardiac drift? Does it have to do with decreasing total blood volume? - I'm not sure if you said this, but is it the case that heart rate goes up to compensate for a decreasing stroke volume from a fatiguing heart?

[@drwilloconnor]

Great questions. When you sweat, your blood volume decreases, reducing your stroke volume. HR increases to maintain your cardiac output. Nothing has to do with your HR fatigue.

[@nickdalfarra3887]

Thanks @@drwilloconnor! Appreciate it :)

[@Sidali1104]

Thank you for this information this is what I was looking for

[@drwilloconnor]

No problem! Thanks for commenting.

[@Sidali1104]

@@drwilloconnor you are welcome 👍🌹

[@MidLifeRunner]

Very insightful , thank you

[@drwilloconnor]

Cheers, mate. Glad you found it helpful.

[@bartekzielinski1645]

And I got many insights from both of your channels, @MidLifeRunner (loved your recent running influencers shorts) and @drwilloconnor (this HR vlog is essential) = so thank you!

[@hikerJohn]

And if you are trail running it's even harder to stay in a zone to the point of it probably does not matter unless you're already an elite trail runner. I just look at what my AVERAGE heart rate was for my 3 hr run/walk. I'm still spending 90% below lactate threshold even with a few fast runs up a steep hill. And I'm 99% below Anaerobic threshold but I do hit it for a few seconds running up that last hill at the end of the course on occasion even if it's an easy run day.

[@MrJohnno89]

Yep, I agree. Because of these factors I look at my average HR across the run. And it seems to be working great for me. Taping Z3 for couple seconds here and there imo aren't going to ruin the over objective of the run. It's only if that HR can't come back down into Z2, I think that's the issue.

[@drwilloconnor]

That's spot on. It's not worth getting stressed over a few moderately hard efforts within 3 or 4 hrs of running.

[@willbilson7210]

What explains a 34 year old male who ran 3 marathons at 2:49, 2:47, and 2:39 ALL at 180+ average heart rate?

[@hikerJohn]

@@willbilson7210 Start young . . . Sifan Hassan is 30 years old . . . 30 is the ideal age for running marathons but not a good age to start running for the first time in your life but better late than never

[@RaoBlackWellizedArman]

Great video! Your explanation of the O2 slow component is fascinating. I have a few questions related to this: Q1. You mentioned that during a run, we recruit more fast-twitch (FT) fibers as we fatigue, which are less efficient and require more oxygen and possibly more fuel. So, one way to improve performance in a marathon is to train not just the slow-twitch (ST) fibers but also the FT fibers. Traditionally, distance runners focus on long runs to fatigue the ST fibers before engaging the FT fibers. However, I'm wondering if it would be beneficial to train the FT fibers by doing fast short repetitions. Would this effectively recruit and make them more efficient, assuming the cardiovascular system is well-conditioned for a marathon? Q2. Does this concept apply to shorter distances as well, given that runners start at a faster pace and recruit FT fibers from the beginning? Q3. Does training in Zone 2 (not long-distance) have any impact on FT fibers? I assume it might not. Q4. Assume you have a well-trained runner. So, their leg muslcles are packed with mitochondria and they're therefore efficient at running. Then, the leg muslces of the runner undergoes significant hypertrophy and hyperplasia through strength training. Would this decrease their overall running efficiency, considering that the newly developed and hypertrophied fibers might not be as efficient as the original ones? Your insights would be valuable.

[@drwilloconnor]

There's a lot to unpack there. Q1 - Specificity is critical here. Shorter intervals prime type 2 and type 2x muscles to be more carbohydrate-reliant. The sweet spot for what you're talking about is "tempo" work where intervals would be 10+min around marathon to half marathon effort. Q2 - Increasing aerobic capacity will improve overall performance from 800m upwards since the predominant energy conversion pathway will be oxidative phosphorylation in the mitochondria. Q3 - Two types of fast twitch (type 2) muscle fibres exist. Those that are relatively fixed and those that are more plastic (trainable) Type 2x. Q4 - Type 1 fibres will increase in size but not number during strength training. Any new fibres that are generated will be type 2. The existing Type 1 fibres won't lose efficiency, and the newly developed type 2 fibres won't be recruited until late in the race, if at all, so their metabolic inefficiencies shouldn't reduce running economy.

[@thomasgerman8825]

I've been watching your vids. Thanks! I ran my first marathon a month ago. Temps high 30s on a gravel rails to trails path and used my coros threshold HR as a guide (which matched your calc). I was expecting heart rate to climb but it never did so I pushed the pace after mile 15, for me from 830-840 down to 800-820 since I was feeling great. Then at 20 instead of my heart rate going up it started going down and things got harder and then I fully hit a wall of some kind at 22. Did I hit lactate threshold and lose my ability to push myself or run out of fuel since my heart rate never got close to maxing out and went down as my ability to keep pace continued to drop.

[@drwilloconnor]

That can happen when your blood sugar drops. You'll lose blood presure and cardiac output.

[@thomasgerman8825]

Thanks. Makes sense... it's also when I felt my body temp drop and my hands got cold after being warm most of the race

[@LukeAClynes]

Hey Dr Will, should you expect some cardiac drift/O2 slow towards the end of any zone 2 training run... eg.30-60mins... and on a training run, would the advice be to slow down to keep the HR in the Zone 2 range? Or is it okay to push into zone 3 towards the end of the training run..? Thanks mate.

[@drwilloconnor]

There will always be some cardiac drift, but I wouldn't recommend allowing your HR to creep into Z3. That shows you’re getting too fatigued, and it'll affect your recovery. It's better to slow down earlier in your run.

[@LukeAClynes]

@@drwilloconnor legend! Thank you 👍

[@simoniles5506]

Both my marathons have been in z4 since the start and somehow didn't blow up in either first one was even a negative split with times of 3:16 & 3:13 I don't fully understand how this was possible

[@TheGetawayMan]

I thought this same thing for a while but realized my zone calculations had to be too low for that to make sense. Garmin (and other calculators) kept telling me my lactate threshold was 170 BPM but I could hold a 2 hour run averaging 181-183 BPM.

[@drwilloconnor]

That's right. It can depend on if you're basing your zones off threshold HR, HRR, or maxHR. Then the zone system you're using can obviosuly impact the issue too. Garmin uses 90 - 100% LTHR for Z4, which would be easy to hold for a marathon.

[@andreataurisano8681]

Thanks for yet another excellent video. Still confused about my own HR though. As a 50 yrs old, not particularly fit male with a measured max-HR of 191 and VO2 max around 49, I recently run my second half marathon in just over 2 hours, with an average HR of 173 and max HR of 183 (and HR above 160 from the start). It's unlikely that my true max-HR is much higher than 191, so then I wonder: How can I have sustained such a high HR for over 2 hours? At the finish line, I was indeed very fatigued and aching at a tendon & joint level, but my muscles didn't feel like I had been running at or over threshold for long..

[@drwilloconnor]

Thanks for the question. Metabolically you didn't run over your threshold for 2hrs. Just because your HR was high doens't mean your metabolic rate was high too. Once you got hot and loss blood volume (from sweat) your HR would have increased without an increase in metabolic rate. That's why I use pace, power & HR together to get a complete picture.

[@bartb217]

Great information. I get a lot of cardiac drift when humidity is high and the temperature above 15 degrees C. A question: I had some 10K races lately where I couldn't get my heart rate into zone 5 (above threshold = 166bpm), but I was able to stay at 164-166 for the last 8km. It feels like I am unable to push to the max in those races, and I run 2 minutes slower than my pb. In some (speed) training sessions I sometimes can get my heart rate to 180 and in my PB 10K I got it up to 178. What can be the cause of this? Can mental stress cause this? The last race I had a very poor night of sleep and lots of worries because of a sick relative.

[@drwilloconnor]

That's the art and science of peaking for an event. From my experience, what you're describing is general fatigue. Whether it's mental, physical, or both can be hard to determine. But when you have a suppressed sympathetic nervous system, you'll find it hard to dig deep and push yourself to those upper limits.

[@bartb217]

@@drwilloconnor I did some tapering and the last "speed" session on Tuesday went great, so I was kind of surprised I couldn't go faster or push harder. The first 5km felt easier than ever, but when fatigue kicked in and when normally your heart rate goes up at that point, It didn't go up and the pace start dropping. So I think it was the mental stress caused the day before. But it also can be the weather that whole week, every training was in the rain and with lots of wind, so physical fatigue. Luckily I have another chance this weekend, hopefully I will be able to push then.

[@drwilloconnor]

A mental skills approach that's always helped me has been preparing for the negative thoughts I know I will have within a race or effort. Whether it's worrying about going too slow at the start or telling myself it hurts too much at the end. Give that a go before this weekend! All the best.

[@edwin5419]

"Assuming it's under 37.5C". Well there goes my runs here in Perth, Australia for the next few months

[@drwilloconnor]

Ouch. Might have to set the alarm extra early!

[@marcuslaw5988]

What are your PBS ? 5k 10k 21k 42k ?

[@drwilloconnor]

Hey mate, 15:46, 32:21, 1:13, 2:37. I'm currently working towards a sub 15min 5km.

[@5kribbles]

"heart rate, it's been around for decades" The earliest known example of a complex cardiovascular system is from a fossil dated 520 million years ago. So... true!