Calculating LT1 and LT2 approximately without a blood test?

Yep - I use 6min steps, with (depending in athlete) 15-25W increments (sometimes confirmed with a MLSS test, but rarely).

The Colab notebook and similar code on my laptop. Every indoor and outdoor ride is recorded on Garmin 530 and dual HRM.

Interesting…seeing these big individual ranges makes it even harder to make sense of one’s own data interpretation…

Did you have any quick recommendations for those 2 showcases given above?
(Like more intensive/raising the roof work for number 1 and more long slow steady state endurance for number 2.)

Yes, will give a follow up with some N=1 anecdotes (maybe in the sweet spot progression thread)… 4 VO2max workouts done by now and so far happy with that experiment…

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I made a test yesterday with a 6 min/step ramp and found my LT1 at 75% of max heartrate. It feels correct to me as it’s the point where breathing started to change. That’s the upper limit of endurance zone 2(out of 7) if you use heartrate.
However, the LT1 power I reached during the test is 82% ftp, in my mid-tempo zone.
My question is: Do you use the LT1 test to change your endurance zone ?

Additional info: my ftp was tested 3 weeks ago. I’m definitely slow twitch, most of my rides were done at 75% max heartrate in the past years, rarely going above. I only started doing intervals and using power zones a few months ago. Endurance zone feels really easy, more like recovery on a heart point of view.

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For people using the Colab workbook, do you get the .fit file directly from your bike computer?

I downloaded mine from Garmin Connect but there didn’t seem to be any HRV data in it.

Edit: Silly me, I had HRV logging disabled.

No - dont change zones - just remember where it fell and if/when you decide to do specific sessions targeting around LT1 then you can use those numbers.

The 7 zone model is not anchored around LT1.

I did not. But I don’t really use a time in zone model to guide my training.

If it helps: prior to thinking about LT1 (and reading ISM training concepts), my training was essentially a sweetspot based model. Standard stuff where easy rides were recovery, long rides were just riding along and then sweetspot/threshold and supra threshold. Look at TR SSBMV2, general build, and that would be an approximation. My prior coach was a sweetspot / threshold guy and we were targeting 15-35 min time trials.

Incorporating LT1, I moved some of that SST/Threshold time down and some of that easy recovery time up. It would sound cooler if I added more detail and had a nice progressive overload scheme to share, but didn’t do anything fancy. Just time in and around LT1 with some harder days ( “stuff” ) thrown in, some race approximations, and accumulating as much time riding in and around LT1 as I could.


Remember to factor in duration. Yes, during that 6 min/step ramp you found a power and HR that corresponded to LT1. But you were (presumably) fairly fresh and the test didn’t take that long. So yeah, .82 IF wouldn’t be outside the realm of possibility. At the beginning of most of my LT1 rides, my power is sometimes 20W higher than previous assessment for about 20 mins or so. It then levels. If I go long enough, it falls :slight_smile: (of course, right? lol)

Try this: ride at your LT1 HR (75% max) and let power just come (or go). Clamp HR and you will not hold .82 IF forever.

Agree with this. Don’t mix or try to reconcile different zone systems, you’ll be stuck on the internet too long if you do that. :slight_smile:

Did total time or TSS go up or stay the same(or lower)?

Yes, up a bit, more consistent, not huge but 50-100 +/- TSS over my SST type programming. From memory was getting a good 8-12 hours per week and hitting 3-4 hour rides regularly. Volume, to a point, has always been good for me.

I did this programming first year of covid. With lockdowns the roads were empty of cars. Couldn’t mountain bike as parks were closed (and also didn’t want to crash and need hospital help). So I rode solo a lot outside. May-June-July looks like consistent 600-650 TSS weeks.

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Training a lot at a relatively easy intensity just flat works. I started using DFA1 alpha around 8 months ago and LT1 is 123-124, so I train 120 and below. My “test” is 90 minutes 118-122 in TT position on trainer, and over the course of that time period I’ve gone from 205w to 243w. I’ve worked with a coach for 6 years and what we’ve morphed into is him giving me 1 “hard” ride and 1 “hard” run a week depending on time of year, and as much <LT1 cycling and <130HR running as I can handle (I can’t get clean data running for DFA1 alpha). Running pace has dropped from 8:15-8:20 to 7:10-7:20. It’s pretty unbelievable. And these aren’t “new to endurance sport” gains either. I’ve raced since 2000 and am 40 in a few weeks. The best part is with so much easy training I’m actually looking forward to getting out daily and enjoying it - actually look forward to the harder workouts now.


Do you use it also outdoors? Are there differences in values when testing indoor vs outdoor? Maybe not in heart rate but power could be lower indoor.
If you have a garmin 1030 you can use DFA Alpha1 IQ connect to show the value on your garmin screen.
With fatmaxxer you can use the notification to get it on your device for using outdoor. But for my edge 530 that did not work. I only got the notification that fatmaxxer is started :grinning:.
Could be usefull in the near future that extra datafield is available on your garmin or other bike device. Because outdoor you normally don’t use your smartphone I think? For live tracking…could be handy. I think. :innocent:

This is the thing I think a lot of people lose sight of when they go time crunched. Doing kinda hard all the time takes the fun out of riding and you can only do so much before you burn out mentally or physically. If most of your riding is “easy” you really look forward to the hard.

For capping the HR do you cap power at all or are surges to get the HR up quickly ok?


That would be interesting to try out on all my weekly endurance rides, but its only the 1030… Connect IQ Store | Free Watch Faces and Apps | Garmin

Sent a note to the developer asking if there are plans to support the 530.


Surges of up to 10 seconds well spread out don’t seem to have a measurable effect on HR. My understanding is those are ok to add into a few rides here and there as they’re more neuromuscular in nature - note though that they’re surges, not 10x10 seconds hard and 1:50 off. If you surge for a minute though, you’ve just changed your workout. In short, I really don’t surge all that much on the bike. I do however incorporate 5-10 second strides towards the end of runs with walking in between.

Regarding your specific question though, I don’t look at power until after, ever. But I do use it during races and use HR as secondary. So if I’m training my hard ride consists of 2x30 minutes z3/z4 (in a 5 zone model), I’ll do that workout by HR. After the fact I’ll look at power and then base race decisions on what power I’ve seen in training.

I’ve stopped basing much on power in training as it led me down a road of chasing a number that may or may not be appropriate depending on time of day, time of year, work life, social life, etc. HR stays constant


I just use the same HR inside and out and don’t worry about power. Luckily I only have a 530 and can’t get the DFA1 data to pop up. I say luckily because I’ve gone down the road of being too “sciency” with this stuff and it takes away from training enjoyment. So I take the 123-124, keep it below 120 and I feel confident I’m below LT1. Also, per Plews - being in the correct HR zone illicits the correct physiological benefits regardless of power - so if it’s hot then yea power lower, if cold likely higher.


Had exactly the same reaction. Its even in my logbook and mentioned it in one of the threads on the forum. Road riding became fun again. I would look forward to a hard Tuesday session or a fake race (TT) with friends on the weekend. 3-4 hour rides were pleasant. Fitness was pretty good too.

We should start a “not time crunched” movement!!!

Since we’re all having a cool conversation here… I’ve wondered about paths to fitness. There are so many ways to train. I’ve tried a few and for time spent, end up in a similar spot.

So… if all roads lead to Rome it may not matter how you get there,. Then I’d pick the one that brought me the most enjoyment. This more endurance focused plus some stuff approach, using LT1 as a point of reference, sure was more fun than any of the SST type plans I’ve run.

With retirement not far off, going to have opportunity to do this more systematically and see what happens.


For me its mostly due to terrain, I live in a city so rides always have some unavoidable stops and starts. I’ve never found any difference if I hard start or intentionally kept it easy. Even intermittent moderate efforts that are relatively short spread out within a Z2 ride have had no effect on the feeling or recovery afterwords, but I’m used to doing them more in the mid Z2 area rather than high Z2/low Z3 that corresponds to LT1. I’d like to move my training more towards this higher level if I’ll get more efficient gains in less time but if riding right on the cusps, random efforts may more likely push me over that boundary hence my questioning.

Interesting, I know that on the Emperical Cycling podcast , they came to the conclusion you should ride them based on…RPE since both power and HR will vary a bit day to day and even within a ride depending on drift/dehydration etc.

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I think the thing is that many of us learned along the way that if you push it too hard and the bike is no longer fun, eventually you will reach burnout. So even if the path to fitness is the fun path that may not be the most efficient, its the most rewarding and has the best chance at consistency over time.