LT = FTP to me.

Also LT is roughly between levels 4 and 5.

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Brian

Friel is likely talking about the nebulous - and not really overly accepted term - "aerobic" threshold, which is the point at which your body starts to accumulate more lactate than it can process. ~75% of FTP is correct. Basically, it's where you start to see BLA, usually a value over 2.0, IIRC. But the analogy I heard used that made the most sense was that AT is when the sink starts to fill up, and LT is when the sink overflows.

LT - Lactate Threshold - is defined by a pretty severe change in slope on a wattage/BLA curve. IME, it's closer to 30min power. And FTP ~= 95% of LT, or LT = 105% of FTP.

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Rapp - I don't think AeT is nebulous especially when you provide a pretty good definition of it. LT should be a threshold detected in lactate testing. Your definition works, some would say it has to be a change greater than 1.0 to avoid errors in measurement.

To the OP: It is best understood this way IMO. There is a first and second threshold in lactate testing. You can determine the first as the first noticeable increase in lactate (some would call that aerobic threshold or 70-75% of FTP). Then there is a second threshold which is harder to measure. But, the change of slope works as an easy definition. And, I agree with Rapp, it is higher than FTP. Some people call this LT (which is poor in my opinion). Years ago it was commonly called anaerobic threshold but english/philosophy majors did not like that definition.

When you read Friel, Carmichael etc., you need to figure out how they are testing their athletes and then you will know what threshold they are talking about. There is no consensus.

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So is it not correct to state LT is the pace you can race at for 60 minutes? For example, I am training to race 10 miles and shooting for sub 60. What pace would you say is LT then?

No, that would NOT be correct to say. FTP is the pace which you go for 1 hour. If your race is only 10 miles (say, 22 mins), then you can certainly race "above" FTP or LT. Theoretically, if you stayed right at your lactate threshold (say, 2.0 mmol of blood lactate), you could go for hours.

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Fatigue is biochemical, not biomechanical.
- Andrew Coggan, PhD

I should have been more specific. The 10 mile race is a run.

A major issue is that LT has many definitions and / or multiple terms such as OBLA etc. that all refer to different points
1. Where lactate rises above baseline
2. 2mmol/L of lactate
3. 4 mmol/L of lactate
4. A rise of 1.00mmol followed by a rise of 1 or 1.5 etc etc

So you have to be critical of what the "study" or "article" is actually referring to.

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unlikely, LT is measured with lactate measurements. Hop on a treadmill and do a test. The speed on the treadmill when you hit LT is your LT pace. And that is unlikely your 10 mile pace no matter the definition you use.

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Jordan,

I don't like your phrase "accumulate more lactate than it can process." That's MLSS, not AT.

Here's how I understand it, bear with me. We all have a resting concentration of lactate in our blood. Let's say 0.8 mmol/L. Then we start pedaling and gradually increase intensity and eventually the concentration starts rising fast enough to indicate an inflection point in the lactate vs. Watts curve. This is AT and I agree it's around 2.0 mmol/L. Keep increasing intensity and the concentration of lactate continues to rise but I take issue with your statement because until we reach another inflection point (MLSS) our body is able to process all the lactate, it's just a higher concentration. I like your sink analogy, but I'll add that above AT but below MLSS, our bodies (the sink) has the ability to make the drain bigger so that even though it's more filled up, it won't overflow as long as the intensity is held constant.

Then increase intensity even more and you hit Maximum Lactate Steady State (MLSS) and now your statement is true. Your body is incapable of processing the lactate so constant intensity will mean rising lactate concentration. I thought this is what anaerobic meant and why you can't be anaerobic for that long.

Clearly FTP is bracketed by AT and MLSS and I've always been confused where "lactate threshold" fit into this. Is LT == AT or does LT == FTP?

When people say they are "at threshold" I assume they mean they are at that lactate point where it's just below OBLA and sustainable for more than a few minutes. I thought as we get fit we move both AT and OBLA up and we move "threshold" closer to OBLA. Then FTP is just an arbitrary point between AT and OBLA that you can hold for an hour.

I don't know what the point it. People say "LT" and I get confused. People say FTP, AT, or MLSS and I know what they are talking about.

Jeff

[I confused OBLA and MLSS. Thanks Dr. Phil for the better explanation below.]

Thanks for replies Guys which have given me a greater understanding of LT.

What bothers me is the 2 seemingly different definitions of LT within the same book by Coggan who is an expert in the field.

I am a novice, so it's highly confusing when you are trying to get a handle on the things

Hello Vern et al...

I think the problem here is that we have a whole lot of terminology that people in sport use somewhat recklessly and inaccurately. Let me try to help clear things up a little bit. (Besides all the athletes I coach / sports medicine I do, I work in one of the best laboratories in the world with respect to this stuff). In short, there are really two "thresholds", if you like.

At the low end, we have Lactate Threshold or LT. This is simply the point where lactate rises by 1 mmol / L over exercise baseline. In other words, if you are zipping along at 1.5 mmol / L, and you speed up enough that you reach 2.5 mmol / L, you have crossed LT. This is actually a lot easier to do than most athletes realize. You could ride around at / about LT for a couple hours without much of a problem.

In the middle, we find OBLA, or Onset of Blood Lactate Accumulation, is when you hit 4 mmol / L, irrespective of where your baseline was. This term is not used frequently used anymore, and we should probably avoid it.

At the high end, there is the MLSS, or Maximal Lactate Steady State. This is simply the highest level of exercise we can maintain while maintaining a steady concentration of lactate in the blood. Any higher, and we see a progressive increase even if we maintain a constant power. MLSS is intimately related to the concept of Critical Power, and is probably one of the biochemical manifestations of reaching Critical Power (if you are on a bike) / Critical Speed (if you are running or swimming or whatever). The physiological "stuff" going on at this point is probably what results in the "feeling" of "threshold", and is what is partially responsible for what Andy Coggan calls "FTP". FTP is probably not reflective of some unique, alternative threshold phenomenon. It is just convenient shorthand, and results from your body "understanding" that if it goes much harder, bad stuff is going to happen (like inexorable fatigue). In other words, FTP that you observe in the field by doing something like a 40KTT is probably pretty close to, but just slightly lower than CP in a well trained athlete.

This begs the question, what is CP and how do you measure it? If you did a bunch of all-out exercise tests...i.e. went as hard as you could for 3 minutes, and then for 5 minutes, and then for 10 minutes, and you graphed them on a piece of paper, you'd get a curve. It would be high on the left, and then slope down to the right. The place where it seems to level off is CP. You can also make the same graph by using joules (this is easy... watts = joules per second), and you get a straight line, and the slope of that line (rise / run) is equal to CP. (PLEASE NOTE: This is Critical Power, the real scientific one, not the bastardization used by many people to refer to the hardest they can go for some period, like "CP30" for "the hardest I can go for 30 minutes).

Basically, it goes like this. As you cross LT, you begin recruiting less efficient muscle fibers, which tend to use more glycogen / carbohydrate and less fat for fuel. The result of this is an increase in lactate in the blood. This is not a problem. The lactate is taken up by other cells / organs and is metabolized. (Lactate is an energy-rich compound, not a waste product. It doesn't in and of itself cause fatigue). In triathlon, it is a problem only in the sense that your body glycogen / carbohydrate stores are limited, and that you can "bonk" if you aren't getting enough carbs in while you race (if the race is long enough). Additionally, we see the emergence of what is called the "slow component" of oxygen use. In other words, let's say your LT is 170W (not unreasonable for an age-grouper). Below 170W, you are using some constant amount of oxygen. If you made a graph, you'd see your oxygen use rise up as you started, and then become a straight line. Now, if you ride 180W, what you will see is that your oxygen use seems to kind of level off, and then (maybe a minute or two later) there is another "hump". In other words, it appears as though your body suddenly realizes it needs more oxygen to do the job. However, this second "hump" also levels off, so you again end up with a steady state of oxygen use. It is just that you are using more than you might otherwise have expected.

The key is that so long as you stay below Critical Power, your body is able to maintain a physiological steady state. After several minutes, oxygen use levels off, lactate concentration levels off. In the muscles, the concentration of creatine phosphate (PCr), ATP, inorganic phosphate and hydrogen ion (i.e. pH) stabilizes. Once you go hard enough to cross Critical Power, bad stuff happens. In other words, let's say your CP is 240W. If you go to 250W and hold it, things get interesting. Even though the work rate is not changing, there is still a progressive increase in the amount of oxygen used, a progressive increase in lactate concentration in the blood, and a progressive decrease in ATP, PCr and pH inside the muscle. It is very cool, because you cat actually watch a lot of this stuff happen with a specialized MRI setup. Eventually, you reach some limiting level of the concentrations of the other stuff, fatigue, and must stop, or at the very least drop to some much easier intensity.

I encourage people to stop thinking in terms of lactate. Everyone does it, because it is so easy to measure. However, it is really just a very indirect market of some much more important / interesting stuff that is going on in the body, most of which is not easy to measure without expensive gear. From the perspective of the average (or even professional) athlete, it is simply important to realize that you don't want to be crossing CP with any significant frequency or for any significant duration if you are expecting to do your best in a triathlon, particularly a long course triathlon.

Hope that was helpful.

Phil
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There is a simple source of your confusion and that of many others here,

Joe Friel's books refer to LT as the pace you can hold for about an hour. Or the pace you hold for the last 20 minutes of a 30 minute time trial.

The Allen and Coggan book refers to LT as either the point at which your blood lactate hits 2.5 mmol/L or possibly the definition Phil puts out above of 1 mmol/L over baseline.

What Friel calls LT and what Allen and Coggan call LT are different points. The Friel LT is harder and is much closer to what others call MLSS.

So be aware of that when reading that.

There will be much discussion on this, but what I outlined above is the source of your confusion.

on my reading of the Coggan book at the start he seems to suggest LT is about the same as FTP and also in a 2003 paper states

"Given the limitations of laboratory testing as discussed above, probably the easiest and most
direct way of estimating a rider’s functional threshold power is therefore to simply measure their
average power during a ~40 km (50-70 min) TT. This highly pragmatic approach is justified by
laboratory research showing that the power a cyclist can generate for 60 min correlates very
highly with, but is slightly greater than, their power at LT (defined as a 1 mmol/L increase in
blood lactate over exercise baseline)"

which seems to me to state the same thing again, so Friel and Coggan use differing versions of LT and yet both seem to say they are, as near as damit the same as FTP

Thanks for taking the time to explain Phil,

You are misinterpreting what I have written. Specifically, by "slightly lower than" I was referring to the difference between LT and OBLA*/MLSS/CP/FTP that Phil so nicely described.

*I'm throwing OBLA in here as well because even though it is defined as corresponding to a lactate concentration that is lower than usually found during sustained exercise MLSS/CP/FTP, the way lactate testing is normally performed (i.e., with exercise bouts too short for lactate to reach a plateau in the blood), OBLA ends up being the same, and sometimes even higher. Indeed, the OBLA approach was originally developed as a means of identifying MLSS/CP (FTP not being coined yet).

Well said. All I might add would be that:

1) the non-linear increase in blood lactate concentration is due many factors, not just a progressive recruitment of more glycolytic motor units; and

2) the slow component of VO2 develops above MLSS/CP/FTP, not above LT.

Thanks all. As a newbie to "scientific" training there's some good stuff here and it has helped me a lot.

I have a degree in biochemistry/physiology (albeit a few decades ago!) so I have no problem understanding the principles, but some of the terminology and the way it is applied does seem to be all over the map at times!

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Agreed.



Not agreed. See Burnley and Jones (EJSS , 7(2):63-79, 2007) for a nice review, or Skiba & Jones (JAP, Jan 2011, in press) for a brief summary and commentary on Joyner et al and how this is particularly important with respect to the 2 hour marathon (and in fact triathlon).

The current / modern view of VO2 kinetics is that it can be simplified into 4 domains: Moderate, heavy, severe, and "extreme" (though what you call the last domain depends upon who's lab you work in).

Moderate = Below LT
Heavy = Between LT and CP
Severe = Between CP and VO2max
Extreme = Above VO2max.

In the moderate domain, it is possible to model VO2 kinetics with a simple exponential. In contrast, the heavy domain is characterized by the emergence of a slow component, which eventually stabilizes and can be modeled with a second exponential term (See the above referenced Burnley / Jones paper; in addition, Pringle et al 2003 and Krustup et al 2004 for some suggestions on the actual mechanism at work). This phenomenon has been the source of much debate, but the emerging consensus view is that it is indicative of the recruitment of higher-order (type II) muscle fibers, which have different metabolic properties. Above CP, this slow component remains, but does not stabilize and will in fact lead to the subject eventually attaining VO2max and ceasing exercise, despite a constant work rate / power output.

Phil

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Dr. Philip Skiba
Scientific Training for Endurance Athletes now available on Amazon!

You are misinterpreting what I have written. Specifically, by "slightly lower than" I was referring to the difference between LT and OBLA*/MLSS/CP/FTP that Phil so nicely described.

Ok - thanks for that, please bear with me then on the second part of my OP (probably my error again):

On page 315 of "Training & Racing with a power meter" LT is described as

" ...From the perspective of most athletes and coaches, LT is a relatively low intensity, approx corresponding to the transistion between Levels 2 and 3"

The transistion between 2 and 3 is around 75% of FTP according to the Power levels table (and ride duration of up to 300 minutes) and so is way off what FTP is. (ie. Not slighlty different)

Are you saying that most coaches and athletes get the perspective too low..

By "slow component" I was referring to the inexorable upward drift in VO2 over time, not the fact that you can identify a 2nd exponential on the way to plateau (and let's also not forget about the initial jump up in VO2 right at the onset of exercise).

IOW, you and I seem to be in agreement after all, i.e., VO2 will eventually stabilize as long as the exercise intensity is below critical power.

1. In this context, you need to think in terms of the intensity factor associated with the cut-off between levels 2 and 3 (which is 0.85), not the way the levels are defined in terms of average power relative to functional threshold power (which is skewed downward to account for the variability normally associated with cycling outdoors).

2. What I am saying is that most coaches and athletes have come to believe that LT is a much higher intensity than it really is.

This is one of the major problems with these terms. A lot of different folks use them differently. I think Dr. Phil gave the best explanation, but the Ex-Phys I worked with (Canadian, so maybe that's the problem!) referred to them as AT & LT. <shrug>

In any case, Dr. Phil and Dr. Coggan have provided really good answers, way better than I could have, and I'm glad to update my vocabulary with what they've written.

To jump to the topic of FTP, it's important to really understand the actual term itself. It's FUNCTIONAL threshold power. What makes something "functional"? I would say it's relevance to an actual application. I.e., if you are racing a 40km TT, then your functional threshold power is the power you can hold for 40km. For women, who race 20km, I'd say their FTP is their 20km power. FTP = 60min is *somewhat* arbitrary. If you are a 10km runner, then it could be anywhere from 26:24 up to 40min. the point is that it's the intensity you can sustain for the duration required by the event you are choosing to participate in.

This is why FTP is both incredibly useful AND incredibly problematic. It's a term that's very relevant to performance - because it's reflective of ability for an actual event - but it's basically unreflective of physiology. There's nothing special about "an hour" other than it's about how long it takes a lot of people to ride the standard UCI TT distance. As Dr. Phil points out, there's no threshold at an hour where things suddenly change.

That's also why I don't really buy into the "sins" of calculating FTP *for the purpose of calculating power for OTHER races - HIM, IM, etc. They are only sins if you are racing a 40km TT. That's my opinion anyway. Figuring out CP is what matters, because that is a physiological construct, and there *appear* to be marked % figures about how hard you can ride for various duration events.

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I disagree with your assessment.

For starters, the reason you can't define "functional threshold power (or pace)" as simply being the relevant race power/pace is because the intensity-duration relationship is non-linear. You therefore need to pick a point that is far enough out on the curve that you are on the quasi-plateau. In particular, focusing on efforts as short as 20 km/20 min can lead to mistakes in understanding, and hence in training.

For finishers, the power (or pace) you can sustain for about 1 h is directly reflective of your physiology.