Lactate Testing - Data and Results

I don’t know the reasons why (someone here might be able to explain it better).

But no fructose either before the test, nor under the test. Just have water.

This is a pretty good article: Blood lactate testing protocols for cycling — High North Performance

(The article doesn’t cover your question though)

1 Like

The short reason, without the biochemistry, is fructose intake can increase lactate levels in blood 20-30% according to tracer studies. So if you eat sugar before a lactate test you will get a higher measurement than when fasted.

Passage below from this reference and I’ll leave you guys to go down the rabbit hole if you wish:

In the tracer study by Rowland and colleagues [82], blood lactate concentration changes were compared in 10 men under exercise using oral test solutions of 13C-labeled glucose + 14C-labeled fructose (at 0.6 g/min glucose + 0, 0.3, 0.5, or 0.7 g/min fructose). During the 2-hour study period and compared to glucose alone, plasma lactate amount increased 31% and 24% under the glucose + fructose ingestions at 0.6 + 0.5 g/min and 0.6 + 0.7 g/min, respectively.

A non-important aside, I’m taking a break from web forums and social media, so not posting for a bit. However, as the thread originator, I receive emails when folks post here. Saw this question on fasting and fructose and wondered what the mechanism was so had a look. Carry on and happy testing!


A follow-up to Brian’s post of the charts from Gordo Byrn (which come from a book by John Hellemans). Bryn has a longer explanation on his substack page which I would encourage folks here to check out as it has a bunch of lactate stuff.

Of particular interest to lactate testers: The B or steep pattern is sometimes called the holy grail for endurance athletes. It takes certain training methods, and time, to achieve that type of profile.

Here is Gordo’s sub stack: Cycling As A Foundation For Metabolic Fitness


last week I saw an interesting post on Twitter showing:

  • one person
  • two very different lactate curves
  • one from 4-min stages, and one from 10-min stages

thought I bookmarked it, will post if I find it again.

But that makes perfect sense.

Any metabolic measurement is dependent on the slope of the ramp and lengths of the steps.

Any lactate curve you see has transient effects built in. The magnitude of transient effects are larger the steeper the slope of the ramp and the shorter the stages. This applies to VO2 measurements, too.

To build an ideal lactate profile you have to do several steady-state workouts and develop a lactate surface (time, power, bla). But of course there are limitations to doing multi-day observations.

I have a textbook or three that covers this topic specifically.

Could it be the one you are referring to ?


thats it, thanks.

1 Like

The red curve looks algorithmically fitted (equation unknown) above 210w as there are no additional data points. Compared to the blue curve where there is real data. To my eye, both data sets are roughly equivalent.

1 Like

I missed the extrapolation when first viewing on Twitter, and it was clear when viewing a second time after posted here.

1 Like

I did a new test today - these were the results:

Power Time MMOL
Baseline 1.4
100 14 1
115 8 1.3
130 8 0.8
145 8 1.8
160 8 1.7
180 8 1.5
160 1 1.5
200 8 3.3

I went back to to 160 because I was feeling like RPE was too high to still be in Z2 - I wanted to get a confirmatory reading.

Interestingly, these was the DFA Alpha 1 from AI Endurance:

Basically spot on.

I wonder if the reason the lactate went down from 160 - 180 was my aerobic system was still kicking in. Or maybe it’s just the inherent margin of error in the test.

Interesting about the DFAa1. From what I’ve read recently the threshold of 0.75 is very personal. A bit like the 220-age thing for max HR. The threshold appears to be the point when it plummets AND doesn’t recover.

anyone have thoughts on the following?

  1. does testing with DOMS affect results? if so, is it most ideal to test after a rest day? I feel like I live most of my life with some degree of DOMS anyway…

The following paper made me wonder when it’s best to test, especially for those on a lifting regimen alongside their cycling: Effect of exercise-induced muscle damage on the blood lactate response to incremental exercise in humans - PubMed

  1. is it MOST ideal to test in the morning while fasted or should you test under conditions similar to those you’d be riding in anyway (pre-workout nutrition consumed, etc)? Or it doesn’t matter, just be consistent between tests.

i agree. at nearly 52 yrs old, i rarely have a day without some level of grumbling doms, aches etc. usually 30 mins into a session i’m all good.

i’ve a question for the lactate aware: if riding right on that LT1, even slightly above for short periods, can lactate levels start to fall, as fatigue rises. i’ve notice this during this mornings long (3 hr) 0.75IF session. i’m thinking that fatiguing faster twitch fibres simply start producing less lactate, perhaps due to under fuelling or an increase in other metrics. i had about 5 beats increase in heart rate as time went on, however i measured a decrease of 0.5mmol from 1.7 to 1.2 over about a 30 min period close to the 2 hour mark. i did fuel with cereal bars as i went and never feel low.

So…completed my first test (goal is LT1 so did not go to far…). FTP is around 270W.


Step 5 was not a good value I think. Afterwards step 6, 7 i did two strip checks. No analyse the data…
LT1 between 215-230 I guess?



I plot a quick graph (and correct some values).

So LT1 between 217-229. Is it ok to do another more detailed test? Or is this not usefull?
This protocol. Warm-up 20min(30?) at 150W and then 10min steps:
10min 200W
10min 210W
10min 220W
10min 230W

And take a sample every 5 and 10min? Or just one sample 10min?
Does this test makes sense or is it just to detailed?


As this thread was interesting and useful to read, would like to share my testing data as well.

Context: I was heavily influenced to take up lactate testing by the success of Marius Bakken, Ingebrigtsen brothers and, lately, Norwegian triathletes. Their focus on intensity control seems as one of the key factors enabling them to maximise their volume at both high and low intensities, and making sure that they do not overtrain. On a personal level I do not enjoy suffering in noncompetitive environment (only in races), hence any testing means that involve maximal or close to it efforts are something that I would like to avoid. It also means that I could be “undertesting” and unable to clearly evaluate my fitness markers. Now, lactate is by no means foulproof as it usually involves just a single measurement every X minutes, however, you can always redo measurement if it is suspected to be incorrect and you can confirm your test numbers by testing during workouts to see if you are in the target intensity zone.

I am currently at around 86kg (190lbs), so results are low in both absolute in relative terms. The first test comes after 6 weeks of easy riding which comes after around 2 years of very sporadical running and cycling.

From the first test until the third I averaged almost exactly 10 hours per week of cycling. Distribution of it can be found below. Majority of hours was easy riding on trainer from 155 to 180 watts (increased throughout time), some light commuting and workouts. I would usually do two workouts a week and they would be pretty similar, something like 20’ @ LT1-20w + 5 x 5’ @ LT2. As mentioned, I do not like to force myself in workouts, hence RPE in absolute majority of workouts was 6/10.

Throughout time as my fitness got better, I was able to slightly increase intervals volume by maybe 20-30%. After the second test where my LT1 and LT2 were extremely close, I split focus between more LT2 work (30-40 minutes per session in intervals from 5 to 12 minutes and 5-3:1 work:rest ratio) and work above LT2 (which historically was neglected), where it would be something like 2 x 20’ @ LT1-20w + 5 x 3’ @ 110-115% of LT2 with equal rests.

Most of work was done at low/low-ish cadences (erg mode on trainer) as I feel that muscular endurance is major limiter for me, while more general parts of cardiovascular fitness are better developed by my previous running experience. There were no planned down weeks, I was focusing on just having nice and steady build, however, there were few minor interruptions due to life. I found HRV data from FR955 to be useful tool to confirm my own feelings and preventing me from training/forcing issue at some points where I may have done too much if I did not have an objective HRV measurement reinforcing the message that maybe it’s better to take it easy today :slight_smile:

From my experience I am also not good with sudden training overload as I cannot recover properly, hence for me it’s better to keep steady training/life stress instead of going for hard-hard-easy or similar approach (in terms of microcycles). This seems to be consistent with some studies on recovery differences betwen more ST and FT athletes. I have had opportunity to test my muscle fiber composition in quadriceps three years ago. It was roughly Type 1 - 40%, Type 2A - 45, Type 2X - 15%. Test was after 5 days of no sport activities, so type 2X is probably lower on a daily basis and I would expect whole distribution to have shifted somewhat to more oxidative side.

At the moment, I would calculate my LT1 as 290w (as it rises from 1.3 to 1.8 from 290 to 310 watts) and LT2 as 330w.

Note: 20 minutes warmup with 6 minutes steps and 1 minute breaks in between each step. Lactate tested from finger with Lactate Pro2. For test #2 and #3 I am not continuing tests after I get >1mmol jump per step since I am only interested in identifying LT1/LT2.
To illustrate power at threshold relation with maximal power on 12/31 I was able to hold 15’ @ 370w and (perhaps wrongly) expect that in race situation I would be able to hold those additional 5’ until 20’. As mentioned, I do not like to suffer in training. Lactate after 15’ was at 9.2 mmol. At that point I was at slightly lower fitness than at testing #3.

Thank you all that have contributed to thread, it’s a very interesting read.


Not necessary to retest imo, while not perfectly flat at the beginning, it provided the information you needed to narrow down lt1


Did you maybe take gel or something sugary beetween 230 and 245?

No, I think it is normal that my lactate went higher, because CP around 255-260