Zone training for Runners | Is Threshold running the best?

[@sousa9991]

I am an 69 old runner which was stuck around 5.50 min. per km now after doing your home gym drills for about a month, I am running 5.10 min per km, it works, we need to put the work and be patient, I really like your videos, keep up the good work

[@greganikin7003]

This is very scientific way - think in minutes. Stress doesn’t know miles or kilometers. Stress knows time only. Absolutely great video!

[@grzegorzkrajewski1095]

For majority of amateur runners Zone 1 is a fast... walk. Not running.

[@stephenscullion262]

I would say so, and me day 1 at altitude today haha

[@bobbydiner0]

It’s also highly dependent on how you define the zones, do you calculate by % of max HR, by % of HRR or go to a lab to take a test. I haven’t taken a lab test, but as an example, depending on if I calculate my zones by % of max HR or % of HRR, a heart rate of 127 is for me either in zone 1 or zone 3. By feel it’s zone 1 so I use that.

[@everaldoalmeida4924]

@@bobbydiner0 is possible calculated my zone from my pace ?

[@erics7226]

Guess I'm in good company

[@dbo4506]

Hahaha facts. I’m flat out trying to stay in z2 😂

[@Gunnerzfan79]

I've watched copious amounts of running videos, and this is absolutely one of the most efficiently informative and useful on KZbin. Great video.

[@stephenscullion262]

Thanks a lot

[@ShervinShares]

10:34 doing them on hills - i've been doing them on a track & I think that's whats caused my injuries. Thank you for this tip!!

[@JessyGoldthorpe05]

Nice to see another running KZbinr watching other runners content!!

[@00StefanMizzi00]

Great content Stephen. No bullshit, just giving us pure running knowledge from your professional experience. Hands down best running content creator. Thanks!

[@AFlamingSword]

Absolute GOLD. Best content on Running KZbin for those interested in actually learning and improving. Thank you Steven for sharing. Coming from the MAF cult this is a breath of fresh air.

[@RaoBlackWellizedArman]

Definitely agree. What a meaningful term: MAF cult! I wasted a whole year "running slow to become faster" which never happened and made me even slower!

[@walshjm2712]

​@@RaoBlackWellizedArman MAF is incredibly misunderstood and over-thought by many. For me, it's simply a method that helps to keep my easy runs properly easy. That's it. And that easy pace has improved from 7 min/km to 5:35 min/km.

[@RaoBlackWellizedArman]

@@walshjm2712 Good for you. My easy pace has not changed at all. And I didn't misunderstand it. Also, I didn't do it wrong.

[@juliana8113]

I keep my slow runs slow by only allowing myself to breathe through my nose - it's infallible

[@acidgoliath]

@@RaoBlackWellizedArman bizarre because it's proven to be super effective, but I guess not everything works for everyone

[@user-lq5hf1hq7d]

Great explanation of the time zones and efforts. And so timely as I received my VO2Max results today (tested yesterday) with different time zones with aerobic and anaerobic thresholds. What I learned is that my watch was off on my zones by up to 9 bpm. I wish I'd done the test 3 years ago.

[@dgillespie81]

As an old slow fella I think it's always worth thinking in terms of total time for these sorts of sessions. Your 10x1k Threshold is 31 minutes roughly, which is 7x1k for me. 10x1k is going to break me down.

[@Knut1978]

I agree. I think I feel best when doing 30-40 min in treshold, and 10x1k is better done as 6-8x1000 or 8x5 min, etc. Time in the zone matters and it can be overdone.

[@curreretraining999]

This is absolute class advice and knowledge Steve. Best running KZbin content by a long way. Many thanks.

[@RaphaelIgrisianu]

By now the best running channel I found..... by far

[@RaoBlackWellizedArman]

Jesus, I can't believe how invaluable this video was. Many thanks for this. I've been watching lots and lots of KZbin videos on zone training and I must say I was expecting to hear the same old stuff when I saw the title of your video. I was wrong. I neglected the zone 3 area for a whole year and I suffered a lot! Did not make any progress whatsoever in spite of the fact that I was putting more milleage than ever. Can you please make a video about the confusion around zones and why some people advise against working on zone 3 and even call it the gray area or no man's land?! Also, your definitions of zones seem to be a little bit different from the popular 5-zone theory that I hear about most. According to that definition, zone 2 would be what you called zone 1 (120bpm-140bpm).

[@walshjm2712]

Nothing wrong with Zone 3/'grey zone'. The issue is exactly how much you include and when.

[@walshjm2712]

Suggest you look up Alan Couzens and Stephen Seiler - both excellent and renowned sports physiologists.

[@erickoenig8483]

I think he defines HR zones as a % of Lactate Threshold (not max HR). This is more useful for defining HR training zones than max HR (which can be inconsistent depending on the test used)

[@KurtleyWolf]

Beautiful video. Questions I never even had were answered, Those comments at the end really made me feel good about myself. Thanks again ❤️🤟🏾

[@Ben-yw8be]

Zone 1 for me is a slow jog. (3-4 RPE) Zone 2: a bit faster jog (4-5 RPE) Zone 3: Run (5-6) Zone 4: Faster Run (7-8) Zone 5: Sprint (9-10) So little time spent here. I normally use it the last 100-200 meter of a race. Sprint finish.

[@markb4434]

Stop showing off

[@yourpalmal6018]

@@markb4434how is this showing off💀

[@paulgrogan4084]

Hi Stephen. Just started the running master class. Really awesome content. Learning so much already. Thank you for sharing your life experiences with us. 🙌

[@stephenscullion262]

Thanks Paul

[@stevencologne3974]

Yes, also just started doing the masterclass. Stephen has so much information on his regular KZbin and this is another level of organization and gems. I signed up in part as a thank you and support of his regular content and also for the content of the masterclass. Very happy with the relatively small investment.

[@danterrarun]

I wish I had met you when I lived in Ireland in 2012,13 and 14. I used to randomly run by the Liffey with no goal whatsoever 😂 10k one day, 5k the other, then 3 days on a pub crawl, then would go back to running again! I'd have skipped the booze days I'd had a pro approach to the sport! You're very clear on you message, my man! ☘️

[@walt4670]

This video really helped lock in my plan for this season. Thanks for taking the time to record it!

[@Andykerrsailing]

Another fantastic video. I Always see your videos and think I know about that, watch it anyway and learn loads. Such great insight and awareness of what the average runner doesn’t know.

[@stephenscullion262]

Haha like when you watch a movie a second time

[@GaryJahman]

Very interesting and lots of sources saying that zone 3 is a grey area and to be avoided. However I never thought that was correct. Pretty sure that all zones can be trained.

[@stephenscullion262]

Yes I would agree, all can help

[@quengmingmeow]

The argument against zone 3 isn’t that it’s “useless”. It’s more an argument saying that zone 3 is sub optimal than zone 2 or zone 4 for specific things. Angiogenesis? Mitochondrial biogenesis? Heart Stroke Volume? All of this gets trained better at Zone 2. Lactate training…specific to increasing Lactate Threshold? Zone 4 is more optimal at this than zone 3. There’s certainly mental benefits inside zone 3…..which is why I may reserve this for a couple workouts at the beginning of a taper, but nothing in training blocks. When there’s no training time to squander, i see zone 3 only on the way up to 4 or 5, or when I am going back down to 2.

[@brandoncarpenter3517]

Thank you for content like this. I hyper analyze myself all the time with my running. These videos help me maintain sanity!

[@AaronErtsgaard2]

Thank you for sharing this education. I thought id never be able to learn pro training information to condition properly

[@Frakc_official]

Finally someone with qualifications “and” experience bringing sense back into the conversation. Running logic vs Racing logic! If I have to listen to one more influencer from generation HIIT bang on about the panacea of Z2 only. I’ll stop running and take up knitting.

[@heymrguitarman7637]

For us mere mortal runners it's important to understand that the better you get, the harder you can push without HR increasing. So for me I can jog along in Z2 at 6.30km ok but any faster and I sneak in to zone 3. However Kipchoge can probably run a sub 2hr 15 marathon in zone 2. So for elite athletes zone 2 training can be very stressful on the body and too much for every day training. Back to me, I can run every day in zone 2 because I'm not very fit by comparison and that means I'm going very steady and not stressing my body. So your zonal approach needs to change a bit as you progress as a runner. It's worth pointing out, my comments relate specifically to ultra trail running as that's my running of choice. As always there's valid counter opinions

[@marcosquillino9309]

Great Stephen. I'm new in running and with your video i'm learning sooooooo much :) cheers from Italy

[@ZaahirJappie]

That feeling ❤️ when u stumble upon a very important video 🎉

[@michabaszczynski7828]

This is the first time I hear about zones. Very interesting. I was always running with HR around 190-200 for many km's so now I know I did it totally wrong all the time..

[@taavinen]

So informative thank you. Am going to check out your training plans. I’ve been a road and MTB cyclist for 20 years with a focus on ultra endurance. I’ve recently got into running and absolutely love it. My issue has been because I’ve got such a big cardio base I’ve given myself the odd injury. I’ve learnt the hard way fast to manage incremental distance increases to avoid same. As someone mentioned here in another comment, my hardest challenge is actually sticking in zone one. Learning this is my main focus right now

[@patshko9357]

I love your videos Stephen, started running two weeks ago and binging your content has given me all the knowledge I needed to get started correctly 🙏

[@evan-kylelardinois2729]

Thanks for the video! Can you do a series or video about heat and humidity running? Further, how to maximize your results in training and racing? It was hot yesterday (82 deg) and I had to back off my pace about :30 secs. This was my first hot run this year.

[@WillyKoech-p2v]

Hollow sir am willy koech from Kenya am following you every step thank you

[@Gymthingz]

Incline walking is underrated.

[@rodrigogonzalez4938]

I fkn love you!!! I improve my zone 2 from 4:50km to 4:25

[@JM-mz7wx]

Thank you for always reminding us that we should be proud for running.

[@doctornesneb3955]

I just run and listen to my body. Trying to get back to my sub 18min/3mile days in college. Far from it for now but I just started. Good luck to everyone

[@elephantintheroom5678]

A good way for beginners to train zone one is with walk then slow jog intervals, self paced perceived rate of exertion.

[@pk-zm2vd]

Just run my 2nd fastest 10k (on Strava so it must be true 😂) this advice is golden, thanks Stephen 👏

[@miguelmonteiro6197]

Great video as always. Been training for a marathon and focusing a lot on working on different zones :) Cheers

[@marcocote57]

if i have to rate this video, then i give 12 out of 10. really simple to understand! Just Outstanding,!

[@stephencothern4248]

Just realized I’ve been running wrong this whole time lol Spent just under half of my 3 mile run in zone five and I think it was 54% in zone four. Guess I’ll take a break for the next day or two, and then try running in the top end of zone three Sunday or Monday. Thanks for the advice!

[@MrHaggyy]

This one is awesome. I go along with all those definitions. While you can go more specific with what cardio vascular processes are running in the body this is perfect for runners. What's maybe for interesst, the zones depend on each other thats why the attention you want to give each zone is pretty much the same for 5k onwards. Zone 5 for VO2 Max increase the total amount of oxygen your body can get into the system. Zone 1 is efficient fat burning, 3 for carbs, in 2 and 4 we kick in the after burner and trade in some efficency for peak power. So by spending more time in the lower zones you build up the two engines to produce power, by going into 4 and 5 you literally increase the air intake and allow the body to adapt further. While lifting weights we deplet our energy much quicker than we could produce. So this is a mild version of VO2 max version as well. Even tho most scientists wont like that take as it is a different thing to keep constant oxygen intake vs filling a huge gap.

[@Moshie71]

Great post, always wonder what these referred to… Not going to lie I fell off my chair when you said 8 x 1km repeats at 2:55m/km(?), I can’t break 4:00 at the mo* & and my fastest was 3:25 (long ago)… *Getting back into running post covid.

[@benarnold3565]

I love your channel Stephen. Really informative and motivational. I follow quite a few running youtube channels and just found yours recently and it's jumped up to the top of my list. Subscribed

[@austincruz4198]

Gold! You are helping so many people 🤜

[@rolffuchs2737]

So this is some real world stuff that I can use for my training. Thank you!

[@satellitetvIreland]

My trading as a 59y old man is Threshold for 1h on Tuesday and Thursday, Zone 3 Parkrun on Saturday and 15 miles Zone 1 on Sunday, anything is possible with repetition and plenty of rest

[@joelcollings5620]

Amazing hoping to use your vids to help me get some PBS 🎉

[@edwin5419]

Thanks for the clarification. Your zone breakdowns are quite different from most others (like your zone 1 is what most call zones 1 & 2), so this was helpful for translating your other videos

[@trevor81]

For me z1 fast walk, z2 jog-walk, z3 jog, z4 run, z5 all-out racing. It took me 27 years of running to get here.

[@danielstevens8827]

Great information.. so many could learn from this video. 👏🏼

[@jt.8144]

Thank you for this explanation. A true eye opener for people starting out.

[@julianvanostrand3275]

Love your videos, very informative. As a friendly suggestion, you might consider providing your stats in miles also for all those runners stuck in a country too backward to appreciate the metric system. Just makes it easier to quickly conceptualize what you share.

[@andremoh]

Amazing tips as always 🙏🏻🙏🏻🙏🏻

[@k1mfor]

Wait, what? All the experts and recent studies seem to recommend training in zone 2 and zone 4-5, and even call zone 3 junk miles, but this video is saying running in zone 3 is the best way to train? I'm so confused.

[@piyata1816]

He’s Olympic Marathoner, don’t be confused.

[@AlexG-wk3nh]

You need to train all of the zones, depending on what race length you prefer then that will determine what you focus on, so long distance marathons is a lot of zone 1,2,3 I believe. Doesn’t mean you neglect the other zones

[@AAAAAAAAAAAAAAAAAAAAHH]

Follow any elite runner on strava and you will see they are doing mostly 2 and 3

[@tnan123]

Great discussion. Learned a lot from it. Thanks!

[@nicnak4475]

What do you think of the Maffetone training system ? I can never keep it up long enough to see if it works 😀 I'm 68 now, been running 34 years and always trained fairly hard.

[@JoelLong]

informative, detailed, concise, and very helpful! Thank you!

[@tembulimuzamiru]

❤

[@AugherAndy]

Coming back from i jury. Running boston next week. But gonna really focus on zones when im back training properly

[@lcbtcethada3957]

Thank you. Very helpful advice 👍

[@tatchawatnapharat8287]

Amazing. Thank you a lot 😊

[@Aima952]

I'm doing quite a lot of zone 2-3 (MHR) hill walks at the moment, but the closest hill to my house is a progressive incline averaging 16% that I'll face at the end of a half marathon (at the end of the year). I'm doing pretty well on the strava leaderboard for the segment just walking it though and can't wait until I am in a position to try running it in the training block... just lots of base building for now though.

[@belmany]

The BEST explanation of zones. Thanks!

[@TJBrussFitness]

Thanks for the advice. I've been using heart rate training for my weight loss journey.

[@RealStrategyGamingClassics]

Calorie count with food and estimate calories burnt on watch (or phone app) is probably better for weight loss than heartrate. It will estimate. lighter people burn 100 calories per mile. Heavier can burn 125-150 a mile or +25 more if overweight. All calories burnt, not just fat.

[@ajfromwa1]

Another great video but I think you should've also referred your HR to a % of your max. It would be easier to then compare to our zones. As a 50 year old with a max HR of 194, I'm keen to work out where my zones are.

[@walshjm2712]

If you know your max HR, then Karvonen will work well for you.

[@rwg727]

Thanks love your enthusiasm 🙏🏼

[@mona8055]

Thank you so so soooo much! I will try my best to improve

[@KeepFocus023]

Thanks Stephen. Encouraging information.

[@Daniel-qt6xi]

Where do you consider marathon pace in here? You said bottom of zone 3 was about 2hr pace, and for you currently that'd be 3'20/k. Does that mean you consider yourself in 2hr20 shape right now? Super interesting video!!

[@stephenscullion262]

I’d say so, but training you’re not fresh at all, and so that means “while tired” but also, not to confuse things I have a world class running economy 170 by figure, and so I can likely run a marathon at 2-4 lactate I’d say, up to high zone 3 towards the end. It’s not uncommon for my average hr to be 168-70 in a marathon, which is high zone 3 by the end. That takes a lot of training, years of running, gym etc..

[@Daniel-qt6xi]

Thanks for the reply!

[@andrew7223]

Top notch video, thanks!

[@Bruh01234]

can u give us a weekly routines please would really help because im not sure how to fit in running for my cardio and my boxing sessions, thanks fir the vid.

[@richardmiddleton7770]

I prefer 6-7 zones although that's more for cycling where you can be a bit more precise with a power meter. Zone 1 is basically walking and I don't spend any time there on the bike. Mid zone 2 works out almost perfect as 180 minus age. THEN comes 'tempo' which is basically high zone 2, low zone 3. Zone 3 is what we call 'sweet spot' as you get similar benefits as zone 4 without nearly as much fatigue. Zone 4 is your one hour power or FTP although realistically most people would tap out after 30 minutes of this. Zone 5 is vo2 max which is sustainable only for 3-8 minutes. Zone 6 is anaerobic which is sustainable for 30-90 seconds. Zone 7 is neuromuscular which is all out sprint for around 5 seconds.

[@stephenscullion262]

I love the cycling zones, way ahead of running

[@TheSandkastenverbot]

There's plenty of scientific results that show that sweet spot training offers little benefit over training below aerobic lactate threshold (zone 1 and 2) while being a lot more taxing on the body and nervous system. And it doesn't stimulate the same physiological response as threshold training (upper zone 3 or lower zone 4) because lactate levels are still too low to improve lactate clearance. It's not useless, after all race pace for longer races are in that area. But physiologically the sweetspot range is the closest that comes to junk miles of all the training zones. If you want to know more about the current science, google Steven Seiler or watch some of Jack Daniels or Dylan Johnson's training videos. Jack Daniels is one of the most influential running experts of our time and you find a couple of videos on KZbin where he explains different commonly used intensity ranges and what they do physiologically. Dylan Johnson is a professional cyclist with a very good grasp on the current training science.

[@bretts6861]

Having studied elite runners over the course of many years, the median pace is about mile +3 minutes. So your four minute miler type is doing his easy runs at about seven minute pace.

[@pearljam_1]

I would look at the ratios of the two paces not just pace alone if we were trying to extrapolate to amateur runners.

[@yadigarklckaya5989]

Thanks a lot 🙏🏻

[@escapekayak]

12:26 how much difference does skipping zone 5 do and how much difference would skipping also zone 4. The question is : could you roughly compare, for a recreational runner 5-10 hours a week, doing zone 1-3 with also incorporating 4 and 5. Thanks for all the great content.

[@brennangraves6458]

Love the "dequalifications," you give. I've always been of the opinion that the only way to race faster is to train faster, and that means "adjusting," the threshold where you're having to truly work to keep a given pace. Seems straightforward.

[@micksumo]

Love the content! 👏

[@Radmillersk8]

Well done video with good information. Thanks!

[@everaldoalmeida4924]

Muito bom. Informações de qualidade . Very very good, information with high quality. Thanks again

[@leechesterton6506]

Hi Roy, I have' another story "for you ,I was down the tip a couple of years ago,it was getting towards closing time and the bloke in front of me accidentally through his car keys in the crusher and the miserable bloke working there won't fish the key's out,so the guy had to leave his car there and I took him home to headless Cross

[@notsomeNPC]

what a ending i epriciate you !

[@sinangursoy841]

Thank you for the video. Keep it up :)

[@williammaihiwhiu5935]

Thank you😊

[@benoittessier2960]

Great vidéo well done

[@martindattus7064]

Learning day by day on your advices 👏👏💪🏾

[@Lalo_Runs]

Thanks coach Scully 🙏🏾

[@miguelalonsoperez5609]

I personally find 5 zones model quite confusing for people who have no formation in training. I’m sport physiotherapist and runner since 25 years and I moved for the more comprehensive 3 zones model, as is more coincident to metabolic impact on the body. Zone 1 is under LT1 (first lactate threshold), for most people under 75 % HR max but this can vary. Varios studies place 77% HR max at the LT1 in trained athletes so being under 70 % HR max ALL the session is suggested as a secure non lactate region. Notice that HR zones mean you are BELOW the max all time, is not the average so if your target is 70% begin on 60-65 because of cardiac drift. Zone 2 is between LT1 and LT2, where LT2 is popularly known as “anaerobic or lactate threshold”. Is very difficult to be just 2-3 % below LT2 without direct lactate blood samples so perhaps the most cost-effective pace is slightly faster than marathon predicted pace, or for more advanced runners slightly slower half-marathon pace, I personally prefer around 85% HR max to not traverse LT2. Only if you have direct measures may worth being between half-marathon and 10 k pace which is the theoretical LT2 pace. Zone 3 is above 90% HR max, known as anaerobic zone or VO2 max zone despite is nor one or the other exactly… Is the more injury related zone, the most fatigue generating and should be carefully dosed to avoid impact on the rest of training week or other activities. I also personally stick to 10k pace which is the minimum dose that gives an effect: again many trials show that around 90 % VO2 max training is equally effective than 100% VO2 max so the vast majority of endurance runners never go faster. Hope can help a little!

[@nmwhatruliving4773]

Great advices, would you also recommend to add vo2 max training 5-6 weeks before a marathon ? (2:25 goal so 3’26/km) ? Or perhaps it’s more interesting for shorter distances ?

[@cassecassss]

I’m so glad you said your zone 2 is 140-150 because that’s where I feel like my zone 2 is but Garmin is constantly telling me I’m in zone 3 and that I never get anaerobic training. First person who has helped with this frustration

[@codycornell2212]

Heart rates vary person to person. His 140-150 isn't the same as yours

[@cassecassss]

@@codycornell2212 thanks for not letting me have that validation

[@p6hj3434]

Thanks Scully!

[@haon2205]

Can you do a video on Maffetone as well and on what zone will it be considered?

[@PatrickStar_24]

I got 8 weeks before I run a 5k. I haven't ran in over 10 years. I ran my first run (2 miles) and was in zone 4 the whole time. I guess I got to start running in zone 2 😒

[@jortm4075]

probably walking in zone 2 😀

[@PatrickStar_24]

@@jortm4075 Nah I i've been doing zone 2 training for a week. Just ran a 5k time trial on a hilly park course with head wind and came away with a 24:17 time. Problem was I was in zone 5 for 20 minutes. In two months I'm going to go from couch to Sub 20 at 38 years old. Yeah I'm built different.

[@PatrickStar_24]

@@jortm4075 My zone 2 pace right now is a weak 13 min per mile. I am able to sustain most of it for 5 miles though. I think I got a lot of room to improve. I think my basketball background allows me to operate well in zone 5, so I'm pumped if I can build that base and see what I can achieve. Just getting into running.

[@jortm4075]

​​@@PatrickStar_24good job! I run for fun all my life, Never in races though. I somehow struggle in zone 2. Can run a 11min mile i think ( i am European so more in to km) and it feels awfull to run that pace, i'd like to go faster. But at least i can keep running in zone 2 and don't have to walk in between. So there is progress it seems

[@PatrickStar_24]

@@jortm4075 Nice, I am making good progress in zone 2. I heard it takes awhile like up to 3-6 months to see any change but today for an easy run of 5k I ran at a 7:19/km and stayed in zone 2 the whole time which is a vast improvement already. I can't wait till I get to 6:30/km or less and staying zone 2. It's going to be awesome.

[@haimeiyou]

Very very helpful, thank you! One correction: Team Sky is now Team Ineos :D

[@heididaniel1539]

Zone 1 for me is I forget I am running. Two hour long run clear me mind run. Zone two and three develop every week dont mix up thankyou

[@PopaMircea]

Thank you! You are amazing and so inspiring!

[@Chance-ry1hq]

When a 2:09 marathoner wants to give me advice, I listen.

[@tsvetomirpenev9164]

Great info! What happens if you run close but slower than LT, isn't there more benefit there compared to Zone 2?

[@ryanveale4432]

Amazing advice!!

[@ludigracic]

Great informations, but not every person have the same heath rate zones. Someone have max HR of 220 and someone max is 180 so their hearth rate zones would be different. And for folks with low aerobic endurance they should walk or put the trademill on incline until they hit their zone. So heath rate chest strap sensor is mandatory.

[@RogerioLuis-iv2bw]

Ótimo vídeo, parabéns por compartilhar esse conhecimento adquirido através dos anos sobre as zonas de treinamento.

[@kidssport8167]

His zone categories different to my understanding - zone 2 is the 120 to 140 range

[@Audifan8595]

I must be a mutant because these numbers are wildly different from what my zones feel like. When my HR is around 145-155 (via Coros armband monitor), I am running so slowly that it feels like psychological torture. I'm talking 12:30min/mi pace. The last races I did were in November, a half marathon at an 8:01 pace and a 5k a week later at a 7:18 pace. Unfortunately I did not have a sports watch or any way to track my HR back then. When I do training runs at around 8:20-8:30min/mi, Coros doesn't even give me a running efficiency score because my average HR is above 186. But I feel comfortable. I breathe evenly through my nose, my legs and body feel good, and I can speak in short to moderate length sentences. When I do speedwork (usually 800m repeats at my mile pace, so around 3:15 per rep), the highest HR I've seen on myself is 204. What gives?