its caused by fatigue, glycogen depletion or not enough function of the IIx fibers imo
age-related means door number three.
just like my max HR has declined, so have the HRs for VT1 and VT2
@RobertK As a guess, around 80% of LTHR?
bing bing bing
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apologies for the drift, but still HR-based
when I look back at old data from the 90s, my efficiency factor has not changed much at all – still around 2.25 w/HR. What’s changed is that my LTHR was 10 beats higher when I was 25 (30 years ago).
We do slow down with age…
Usually August through October as my main events of the year are complete by then. With nothing major till following Spring.
I find my ability to keep the same pace over many hours at or close to VT1 improves over that period. So call it my all day pace / stamina improves.
It’s not big leaps or anything like that. But suddenly at the end of the three months you look back and realise the improvement there has been. I keep notes on my rides which helps a lot with assessing this. Rather than thinking I’ve improved.
The top end suffers a bit as I’m not doing so much intensity. But the top end soon comes back once I reintroduce more intensity in November and gradually ramp it up towards early Spring events.
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Does anyone think a portable breath analyzer such as a Lumen device would serve as a somewhat consumer accessible way to estimate LT1 based on RQ (RER)? Their company product seams like an incredible untapped tool to allow for Aerobic Threshold estimation without having to use blood lactate. Without it being on the face all the time like a mask I can see it being prone to error, but, I can also see it being used for spot checks. If anything, I am wondering if it could at least allow one to know when I reach my aerobic crossover point relative to wattage. I want to train at my wattage Zone that optimizes fat at the fuel source. A spot check would allow me to know when I go over that point. Thoughts?
@WindWarrior is keeping a running list. Many of the participants on this thread also participate in the above thread.
(and no I’m not following you around…hahaha…but it seems like I am for the past hour).
I actually checked that thread out last week, was going to give the HRV Logger app a try since I subscribe to HRV4Training Pro and they seam very much in the Zone 2 polarized camp over there. Seams like a interesting way to estimate LT1. Or at least attempt to. I actually came to this thought the other day because I realized FirstBeat algorithms on my Garmin estimate my LT2 using HRV (FTP as well). So I asked myself, why couldn’t HRV be used for LT1 approximation too? Behold! This thread with that same thought haha.
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Unfortunately not. In order for the device to work correctly you need to be relaxed with your Heart Rate as near to its resting level as possible. It only give an estimation, on a scale of 1 to 5 of the ratio of carbs & fat you are burning at rest.
Just to clarify. In the polarized model, most of the athletes studied and used to support the model were doing the bulk of their training below lt1, not just the top of lt1, but below the point where breathing or lactate increased. Ism’s suggestions are different from that, as he’s having people work near the top of what is defined as lt1.
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I am not sure how valuable this information is to this thread, but I was actually tested in Inigo San Millan’s lab here in Denver at the Anschutz performance center back in 2016. You simply paid some money, did a few tests, and were prescribed a training schedule. I was a 35-year-old runner at the time and had never tested any of these metrics despite having a solid running career. I was thinking about training for a fast half marathon. I started cycling in 2019 but had no concept of cycling when I went to his lab. I only did the VO2 max test, but along the way, my zones were calculated based on fat vs carbs. I don’t remember much about the general conversation other than being told not to barf in the mask, but I still have my lab report and prescribed training. I was given 3 prescribed zones: Zone 1-2, Zone 3, & Zone 4+ My max HR was 193. My zone 1-2 was 153-162, Zone 3 168-171, and zone 4+ 180+. Again, this is running not cycling.
A few interesting notes from each zone:
Zone 1-2: Recovery and Base endurance. This is from rest up to your aerobic threshold. This is where your body is most efficient at metabolizing fat for energy.
- Zone 1-2 days should be a gradual increase up to the top workload and heart rate in the zone
- This is your recovery or easy zone
Zone 3: Threshold and Tempo. This is just before your lactate or anaerobic threshold and is typical (sic) the race pace for endurance events. Here is where you build tolerance to exercise.
- Always start with your specific warm-up it’s designed to enhance fat utilization.
- Stay at AT/Zone 2 workload for the entire interval.
- If the Zone workload is giving HRs above the top of zone 2 or below the bottom, report back to your coach.
Zone 4-5 Peak or Anaerobic training zone, it is not an all-out sprint. This is where you improve your peak VO2 and burn the highest calories
- Always start with your specific warm-up it’s designed to enhance fat utilization.
- Zone 5+ or Peak VO2 workouts must stay at Zone 5+ workload and HRs for intervals should be zone 3 and above.
It also suggests strength training days where you complete the specific warm-up before strength routine and do strength training 2x per week. No actual lifting or strength program was ever discussed that I remember.
The Warm-Up Page. Lots of notes here. My specific warm-up was starting at an HR of 143 with 2-minute intervals increasing it to 171 over 10 minutes (143, 152, 159, 163, 171). I was given treadmill speeds for each 2 minutes. Notes on the page:
- Warm-up should be performed on all Zone 3 and 4-5 training days. After your warm-up, take a 3-5 min easy recovery. On your Zone 1 days use the first 8-10 minutes to slowly warm-up.
- If your heart rate after warming up is + or - 4 PBM, please notify your coach. (This was underlined!)
- If at any time you feel like your workouts are too easy do not increase speeds unless you have spoken with your coach. We are teaching your body to favor fat and spare glycogen at the highest speed possible, speeding up to soon will decrease your results.
I was given 4 weeks of training. All included 3 days of base building with one day as long aerobic. Plus a VO2 max day and a Threshold day. In order of each week the workouts were:
VO2 Max:
- 10 sets of 2 minutes (180+)
- 11 sets of 2 minutes (180+)
- 7 sets of 3 minutes (180+)
- 10 sets of 2 minutes (180+)
Threshold:
- 6 sets of 5 minutes, 1:15 rest (168-171)
- 7 sets of 5 minutes, 1:15 rest (168-171)
- 3 sets of 6 minutes, 4 sets of 5 minutes, 1:15 rest (168-171)
- 2 sets of 7 minutes, 3 sets of 6 minutes, 1:15 rest (168-171)
Zone 1-2:
- Simply prescribed time. 2 days at 50 minutes (Running) and one long day at 70 minutes. All HR between 153-162)
Okay, long post, but as it pertains to this thread, this is straight from ISM himself. Although, it’s 5 years old and things could have changed.
I did a DFA a1 ramp test with a Polar H10 and AI endurance and sure enough, my AET came out at 157 BPM on the bike. My anaerobic threshold according to AI endurance was 174 BPM. I have a ramp test FTP of 272w as of December (old I know). My endurance celiing cluster on AI endurance shows 228w and 157 BPM which right now for 60-90 minutes I’ll be right around that probably drifting to the low 160s. I did a ride with a 10 min warm up and a set 215w for an hour and my HR drifted from about 150 BPM to 156 BPM over that time.
I am not an expert. Just trying to provide some hopefully interesting data and information. I think the big take away for me is that this upper zone 2 is closer to what most standard metrics consider tempo. I am also curious that the HR +/- 4 BPM is a concern. Most of my reading suggest HR zones can be 10-15 BPM and it’s no big deal but according to this a small difference is meaningful.
In general, my anecdotal experience is that this all lines up. I can hold 173 BPM for about an hour when throwing down a big climb. I have done 2+ hour rides averaging 150 BPM while it’s an effort, not soul-crushing, and somewhere around 180+ I start to see god (turning 40 much more so).
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So did you end up running a fast half marathon? 
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Thanks for this, found that interesting and for me reaffirms that ISMs Zone 1 - 2 are harder than I’d expect without putting much thought into it.
Lot of people still do the easy stuff too hard, but after decades of people drumming in this message “make your easy, easy”, I think some of us (that have possibly taken too much note of this) have probably gone too far the other way.
I think you start to understand some of this stuff more when doing multi-disciplines (sports.)
Individual HR response, age / recovery times, sometimes makes it hard to peg the intensity for certain sessions.
I’m doing the Manchester Full Marathon next weekend, off 55 / 60 miles per week (+ ~5 hours cycling,) and a lot of my General Aerobic runs have not got near my equivalent HR zones (back calculated off your examples, I know it does work doing this but…), even though based on pace I am about 50 seconds per miles quicker than where I should be (with a HR around 100 - 112bpm). The problem is if I run hard enough to get the HR up then bio-mechanically I struggle to recover in time for the next sessions, it is a constant balancing act, and you quickly find out if you went to hard in previous session. It has been a long time since I’ve had the same problem in cycling.
Significantly upthread I asked “how precise do you have to be?”
It seems ISM addresses that (for Peter Attia) here:
Also, for those of you who have done Steve Neal style long tempo (be it by prescription from him or just based on his podcast appearances), you will recognize this type of training, at least in terms of low intensity.
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So did they basically agree (or didn’t disagree) that top of z2 is 2mmol? Attia said he targets 1.7-1.9 for his own z2 rides at least. Their description of the talk test seemed like they were describing a higher intensity than many seem to describe.
They agree that you have to measure it. It’s not a fixed lactate value that you can apply to everybody. Attia targets that because he measured it. That lactate value is where he sees 1) first rise in lactate above baseline, 2) highest rate of fat oxidation determined using gas exchange. ISM explains that he doesn’t JUST use lactate, or JUST use another measure. He is using THREE measures. Fat starting to go down, CHO starting to go up, and LT1 (lactate initial rise above baseline). He is making the point that he doesn’t just look at the highest point where fat oxidation is occurring and just pick that number (FatMax). He is cross-referencing it with lactate and CHO.
It is a fixed value (more or less, with day-to-day variation) at any given time for YOU as an INDIVIDUAL. It is not a fixed value across different riders. So when you read: “ISM says Zone 2 is 2mmol/L” or “ISM says Zone 2 is 1.7mmol/L”…stop. It’s wrong. That’s not what he’s saying. If you’re familiar with Kolie Moore he likes to call this “fallacy of division”.
Attia goes on to point out that it can be a fairly wide range, so what does ISM do? Answer: targets the middle.
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Their 70-80% of max HR for Z2 is also much higher than your typical endurance workout. I just barely hit 70% of max HR with high progression level endurance workouts.
Yep, the first 500 posts on this thread, when we were all trying to figure that out. LOL. sryke (and others) have said this a number of times: this isn’t easy endurance. It’s not “all-day” dilly-dally pace. ISM even says this in this podcast. Easy endurance is his Zone 1.
My personal experience has been more in line with what BTSeven7 said above (although I do train a bit harder than LT1). I’m likely going to get yelled at for this but he’s prescribing…wait for it…tempo. 
Tempo is the new black. Not that you should actually do it. Do what you want. But it’s cool again…under a different name.
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And couple that with the why, which ISM briefly discusses around 1:12:45…
That from a bioenergitcs point-of-view, he wants to stress the Lactate-to-MCT1 and Pyruvate pathways. Which means from an ISM POV, you can train too low (power level where fatty acids dominate). From my POV its consistent with one of his TP blog articles.
Did anyone else catch that?
My numbers were similar to Attia’s and my 120-150 minutes Tuesday key endurance workout starts around 78% HRmax and I push it up to 81% HRmax by the end.
With only a few exceptions, TrainerRoad plans don’t advocate doing a lot of endurance. Therefore I’m skeptical of AT or PL value for endurance workouts.
Depends on who you listen to? From my POV it never went out of style. I’ve been collecting training plans from the top ‘in it a long time’ coaching companies, and they:
- prioritize endurance training, generally ranging from 60-80% of weekly riding
- advocate doing tempo
- periodize a season and after a long base, move quickly thru build to in-season racing/riding/etc.
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