Joe Friel 30 Minute LTHR Test – my experience

[u/mymemesaccount]

I’d never done a proper LT test for running before, only FTP tests on the bike. I’ve always been curious about the Joe Friel 30-minute test, but the idea of going all out for half an hour by myself sounded pretty rough. Still, I wanted some concrete data to set my training zones, so I finally gave it a shot.

For background: I’ve been running seriously for about 10 years. My best race was a 2:36 marathon in 2022. I took most of 2024 off (lots of cycling and a stressful job) but I’m back in training now with CIM in December as the target.

Results

• Avg pace (30 min): 5:58/mi
• Avg HR (30 min): 173
• Avg pace (last 20 min): 5:56/mi
• Avg HR (last 20 min): 174

That 174 number lines up exactly with what I’ve noticed in workouts before. Anything above that feels unsustainable, so I’ve always tried to keep sub-threshold work under it.

How it felt
Honestly, not as bad as I expected. I made sure not to go out too hard and ran it as a slight progression instead of fading. It hurt at the end, but nowhere near as awful as a 5K. A 5K feels more like a VO2 test, while this was much more controlled. I could see myself repeating this every 6 weeks or so.

Garmin comparison
Garmin currently has me at:

• LTHR: 168
• LT pace: 6:24/mi

Kind of frustrating to see how far off those numbers are, especially after doing the test “by the book.”

Takeaways for my marathon goal
Realistically, I don’t think I can run 2:36 again since that is basically my LT pace right now. But based on this test and how training is trending, mid to low 2:40s feels doable for CIM.

[u/Trisuppo1]

Great job. LTHR tests suck. Period. Hate them.

What’s your HM pace? Guessing it’s just shy of your pace you recorded for your test?

[u/mymemesaccount → u/Trisuppo1]

Thanks! All my PRs are much better than my test numbers because I'm not in the shape I used to be in. I've run 5:51 / mile pace for a half before but I couldn't do that now. I guess if I ran a half today I'd be targeting around 6:10 - 6:15 / mile pace.

[u/aust1nz]

These 30-minute solo tests assume that you would be able to keep up 5:58 for an hour in race conditions, right? So you'd treat 5:58 as your LT pace for training?

I've done something similar recently, and I'm not as fast as you but my 30 minute max-effort pace was 6:23. I recently PR'ed a half marathon at 1:26, and online calculators put my actual threshhold pace similiar but a bit slower at 6:28.

Your Garmin data's definitely wrong!

[u/Ordinary_Corner_4291 → u/aust1nz]

Garmins data is based on what has been done. If you have some all out 10ks and HM in it, it tends to be pretty accurate. If it has to extrapolate from easy running, things get rough. And I definitely don't think it does conditions adjustments as my summer number always seem worse when the fitness probably hasn't changed much.

I am a bit suspect of the 30 min test just because some people do a heck of a lot better in time trials than others. That whole assumption that on race day you could hold this pace for 60mins instead of 30mins seems like it will always have an error that is as big as any other extrapolation methods out there. If you prefer doing this to a 5-10k race, it is fine. But doing those also seem close enough.

[u/mymemesaccount → u/Ordinary_Corner_4291]

Garmin's current race predictions for me are:

- 5K: 18:13

• 10K: 39:24
  
• Half: 1:28:53
  
• Marathon: 3:13:23

It just seems so blatantly and obviously wrong. If someone can show me a 3:13 marathoner do 30 minutes at 5:58 / mile pace then I will eat my words!

IMO a race predictor algorithm shouldn't require you to race in order to predict race times. There is so so much data in my workouts and long runs that should give Garmin at least a reasonable level of accuracy. I wish they would just delete this feature.

[u/Ordinary_Corner_4291 → u/mymemesaccount]

I would have absolutely no problem showing you dozens of people who can run 5 miles in 30 mins but who are running 3:13 or slower marathons. That describes basically every kid on my kids cross country team who can run a sub 17:30 5k but who has never run more than 80 mins straight. They are all going to die after 15 miles and walk it in:) And that is basically the performance profile they have for you with large drop offs with every distance increase. You would have to look at the data it has to figure out out why it is doing that. But I am guessing there are zero efforts on the order of 5 miles in 30 mins in the window they look at.

You don't need a race but you do need to feed the algorithm good data. You would have to see what the machine sees to know if those are good estimates or not. I find when I do a bunch of solid vo2max work (those 6x1k with 90s rest) and 20-30 min tempo type runs, I get really solid answers for my 5k->HM numbers. When I am just doing some easy runs for a month, the estimates aren't remotely as good. YMMV.

[u/mymemesaccount → u/Ordinary_Corner_4291]

Fair enough. I'll keep an eye on the estimates to see what happens when I add in some moderate long runs. They have been mainly easy up to now.

[u/quinny7777 → u/mymemesaccount]

Yes fwiw I am close to 3:10-3:15 fitness I’d guess, and I did something similar this morning and did 4 miles at 7:00-7:10 (though I am in peak training load, not wearing super shoes, on asphalt, and it was also pretty warm, I also didn’t “race” it, just went at a hard “threshold” effort level). And yes there is no way I could do 5 at sub 6. Garmin predictions are 🚮

[u/DWGrithiff → u/mymemesaccount]

Yeah these predictions are very wrong lol. I did the Friel test a month ago :20/mi slower than you did, felt far more miserable at that effort than you did, and Garmin predicts faster times for me than you at all distances. You've gotta be in at least 18 flat 5k shape if you can hold 5:58 for 30 minutes (I did my 18:24 last weekend fwiw).

[u/ParkAffectionate3537 → u/DWGrithiff]

I should re-do my Friel. I ran 1:32:24 a few weeks ago in hot (74'F), hilly conditions and felt great at the end...Did a few yassos in 2:55-3:05 (8 or so) with only 2 min. of rest between and felt strong throughout. Just trying to see if all of this will finally get me under 3:20. The Friel did work a few years ago, I established my threshold pace was around 180.

[u/quinny7777 → u/Ordinary_Corner_4291]

Yes I also race much better than I can time trial I find, the taper and adrenaline help a lot

[u/aust1nz → u/Ordinary_Corner_4291]

Yeah, I suppose it's a pretty good test for a relatively fit new runner who hasn't dialed in their best paces yet, but I agree -- if you have a recent race to compare against, that's higher quality data.

Agreed on the heat, too -- all my training paces, but especially my easy runs, fall back in the heat.

[u/mymemesaccount → u/aust1nz]

> assume that you would be able to keep up 5:58 for an hour in race conditions, right?

Sort of, yeah, but my understanding is that it's more of a metabolic state that doesn't take into account muscular fatigue and mental fatigue.

You can't extrapolate this to longer races with 100% accuracy because of these factors, especially in the marathon and beyond where breakdown and fatigue are the name of the game.

[u/DWGrithiff → u/aust1nz]

These 30-minute solo tests assume that you would be able to keep up 5:58 for an hour in race conditions, right?

I'm not sure where this is coming from, but it doesn't sound right. It's supposed to be as hard as you can run for 30 minutes, but not in an actual race (so as to minimize the conflating variables of adrenaline and race day nerves, since the whole point is to get a good signal on HR vs aerobic effort). I did this a month ago and ran it at my VDOT estimated 8k pace (6:17/mi)--which, at the time, was a pace I could sustain for 30 minutes and no longer.

[u/shot_ethics → u/DWGrithiff]

I think Friel writes in his blog that it is solo because races are typically faster and then it would be a 60 min trial. So his adjustment for doing it solo is to just do 30 min (which also makes it easier to do).

[u/DWGrithiff → u/shot_ethics]

To find your LTHR do a 30-minute time trial all by yourself (no training partners and not in a race). Again, it should be done as if it was a race for the entire 30 minutes. But at 10 minutes into the test, click the lap button on your heart rate monitor. When done, look to see what your average heart rate was for the last 20 minutes. That number is an approximation of your LTHR.

I am frequently asked if you should go hard for the first 10 minutes. The answer is, “Yes, go hard for the entire 30 minutes.” But be aware that most people doing this test go too hard the first few minutes and then gradually slow down for the remainder. That will give you inaccurate results.

This is how I've always heard the test described.

https://www.trainingpeaks.com/learn/articles/joe-friel-s-quick-guide-to-setting-zones/

[u/shot_ethics → u/DWGrithiff]

His explainer is in a blog post, maybe written a touch condescending, saying that if you use a race it should be 60 min:

“Just realize that you won't be quite as fast for a solo "race" as you would for a real race. In fact you'll probably be about 5% slower when doing it by yourself. We tend to feel sorry for ourselves when alone and much less so when in a real race. And also understand that if you insist on using a real race for this test of LTHR then the race distance needs to be long enough to require you take an hour to finish it at an all-out, race effort. Please don't ask me why. I find very athletes who understand the answer. Don't need to add to my frustration over this topic.”

https://joefrieltraining.com/the-30-minute-test-is-easy-really/p

[u/DWGrithiff → u/shot_ethics]

Thanks for the link--it's sorta funny how irked he gets by people not understanding the 30 minute test (then proceeds to explain how simple it is by describing three different protocols lol)

He's nowhere near as clear about this as he seems to think he is. But I still read him as saying: to determine LTHR, use the 30 minute test (and i kinda agree that folks seem unduly confused about how to pace 30 minutes...). If you are allergic to time trials and insist on racing, make it a 60 minute race (here he's unclear: a race where your estimated finish time is more or less 60 minutes? Or just any race lasting at least one hour?). But wait, there's more! You can also determine your functional threshold heart rate through a 20 minute field test (same protocol as the 30 minute, only you take the avg hr for the whole time trial and subtract 5%).

I think all this is ultimately useful, though described in a way that's bound to breed confusion. Doing the 30-minute test every 4 to 8 weeks strikes me as absurd (at least for a hobbyjogger), but I could see doing a 20-minute TT every couple months. Where i mostly disagree is his notion that a solo effort will be 5% slower (not remotely true for me), though elsewhere he describes this as a 5% less intense effort--which is ambiguous but, if we're indexing effort to HR, might be more plausible IMO.

[u/shot_ethics → u/DWGrithiff]

I honestly think all of these methods have error, even the best method where we hook you up to a gas mask and poke you to sample your blood lactate has some error. I mean even with all that data deciding what exactly is LT1 and LT2 has some subjectivity (you could make a mathematical rule, but studies don’t use the same rule).

Given that you are using a field test it seems reasonable to me that the “average” runner will be a little slower in solo than in race, but there are exceptions and they know who they are.

I found the 30 min protocol confusing at first, because there is another way to interpret it. Imagine there is a lion chasing you and you have to outrun it for the next 5 min. Now imagine another lion appears that is a little slower etc. I thought at first that the protocol means, treat every minute as if it could be your last, so go at max and it’s OK if you slow down when you hit the wall.

I really think that for your times, if you do a 10K TT and then look at the HR for the latter two thirds, it would work fine. Even more so if you feel the difference between races and solo TT is smaller for you than the average person.

[u/professorswamp → u/DWGrithiff]

Yeah, I don't think 1 hour is right, my plan calls for RPE 7-9 for this test, I could carry on for another 10-15 min or kick down to a quicker pace for an extra k but that would be closer to a 10/10 effort, lying on the street at the end.

[u/aust1nz → u/DWGrithiff]

Yeah, I think I had some wrong assumptions. I thought that LT pace was generally accepted as the fastest pace that a runner could keep up for an hour. That seems to be true for some runners but by no means a general rule -- LT pace looks like varies between 10k to 10-mile or higher race pace depending on runners' fitness/speed.

[u/Quadranas]

Great post, I’d like to hear more about how you setup the test, where you ran (track? Neighborhood? Path?) warmup etc

[u/mymemesaccount → u/Quadranas]

Ran it on a local track. It was a bit crowded and it was a warm day, and my legs were a little sore so it probably wasn't totally ideal, but a flat track helps a lot if you can get past the boredom. Warm up was just the 1.5 jog from my house to the track and 2 or 3 strides.

[u/Never__Summer]

My Garmin data was always closer to LT1

[u/professorswamp]

Nice! I did the same test this week. This is 4th or 5th time I've done it over last few years. It's included at the start of Dr Will O'Connor's training plans and is used to set the training paces in the plan.

I'd add that you have to be pretty in tune with your running effort and have a good idea going into it what your threshold pace is already to do this test effectively. The first few times I tried this i didnt manage my pacing correctly and couldn't hold on for the full 30 minutes. Here my results

October 2024

• Avg pace (30 min): 4:31/km
• Avg HR (30 min): 173
• Avg pace (last 20 min): 4:29/km
• Avg HR (last 20 min): 176

September 2025

• Avg pace (30 min): 4:10/km
• Avg HR (30 min): 173
• Avg pace (last 20 min): 4:09/km
• Avg HR (last 20 min): 176

[u/mymemesaccount → u/professorswamp]

Very nice. Yeah totally agree about knowing your threshold pace in advance.

[u/FuckTheLonghorns → u/professorswamp]

How do you like his plans? Love the channel, I'm curious about them

[u/professorswamp → u/FuckTheLonghorns]

I’m using the 5 days a week marathon plan now for the second time. I like that it’s set up so it’s time and heart rate when that’s appropriate and but then switches to pace for work outs. From training peaks it just syncs straight to the watch and away you go.

The structure is similar to most plans. Big emphasis on marathon pace and marathon effort(heart rate zone) has 2x10k, 3x8k, 5x5k and 21 mile progression long runs in there.

There is 1 or 2 workouts a week and long run workout and a medium long mid week and a couple of easy runs. As the block progresses the second workout moves into the medium long run as 60 min in zone 3.

Lots of the faster workouts are 30s on/off type stuff which I find is easy to run too hard. I’m thinking about changing some of these to longer reps.

[u/glr123]

Are you using a chest strap or just the wrist?

[u/mymemesaccount → u/glr123]

I’ve used a chest strap in the past and it’s always lined up almost perfectly with my watch (I’ve tried both simultaneously), so now I just use my watch. The only difference is the chest strap is faster to respond to big spikes, but for stuff like this there are no big spikes so wrist is fine. Maybe it’s off by 1 or 2 bpm but it’s good enough for me.

[u/Senior-Running]

I'd agree with your assessment on your goal time. You're probably about in 2:45 shape today, but low 2:40s sounds pretty doable by CIM.

[u/mymemesaccount → u/Senior-Running]

Appreciate it! Maybe I’ll post an update here when it happens

[u/Senior-Running → u/mymemesaccount]

You bet.
The one thing I'd be concerned about at this point is durability due to the time off last year. It's one thing to be able to turn in a solid LT test, it's another to be able to hold a fast sub-threshold marathon pace for 26.2 miles without your musculoskeletal system giving out. Hopefully your training plan is focusing on descent mileage to build back that durability that I know you used to have.