AT vs LT (What's the difference?)

Triathlon Forum
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ANAEROBIC THRESHOLD. (Braunwald: Heart Disease: A Textbook of Cardiovascular Medicine, 6th ed.) …etc.

Yes, of course there are published definitions. If you look farther into the library stacks, you’ll find that they diverge. Some replicate other definitions (LT, VO2max, etc.), others break new ground. The definition you found occurs at nearly the exact point of LT as defined above. It’s the gas-exchange version of finding that first inflection point, and is even more cumbersome to do in real life than blood-lactate testing or HR testing.

Not that the definition you provide is wrong. It’s just that I don’t think it informs us the way that simpler and more widely accepted benchmarks do.

None of this matters if we follow a power-duration paradigm instead. After all, it’s sort of hard to do a 4-hour training ride dragging a metabolic cart around with us and breathing through a tube. :wink:

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we can happily forget all about this LT and AT and AeT stuff…

Maybe that’s a good idea! Or at least be clear what you mean when one says LT or AT. There’s a big difference between the 2.5mmol lactate/~3hr effort LT and the 1hr-TT effort (does this correspond to ~4.0mmol lactate number I see sometimes?) LT, but people use the term to mean both. As a short course triathlete the latter number is more useful for me.

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Good explanation.

According to McArdle, Katch and Katch, Essentials of Exercise Physiology

"the term anaerobic threshold originally defined the abrupt increase in ventilatory equivilent caused by non metabolic carbon dioxide production owing to lactate buffering. Some researchers believed this point signaled the body’s shift to anaerobic metabolism (lactate formation) and therefore proposed the anaerobic threshold as a non-invasive measure of the the onset of anaerobiosis. **Subsequent research **shown that the ratios of VE/VO2 or VCO2/VO2 do not necessarily link in a *causal *manner with lactate production or accumulation in exercise. Even if the association between ventilatory dynamics and cellular metabolic evens in noncausal, useful information about exercise performance can be obtained by applying these indirect proceedures"

Sounds like there is a quasi relationship between the two, AT relates to gas exchange (increase in CO2 production), LT relates to the increase in blood lactate. Both require testing equipment not available to most of us. I agree with previous posters that power or pace are better indicators, after all, that is what a race measures.

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whoops!

should have said “cellular and metabolic events is non causal”

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…and the 1hr-TT effort (does this correspond to ~4.0mmol lactate number I see sometimes?) LT, but people use the term to mean both. As a short course triathlete the latter number is more useful for me.

I think the 4 mmol level is near to the 1-hour TT effort, but I’m not certain.

And, I think that the 60-minute TT power benchmark is useful to all athletes at all distances. A short course athlete might spend proportionately more time at the higher percentages of that power, and IM folks would spend more time under it. But, the benchmark is relevant – and very important – to both.

True “LT power” explains (“predicts”) upwards of 90% of the variation in power output of *any given longer effort *across different athletes. By extrapolation, so too would 60-minute power. The power-duration paradigm is useful and valid for all endurance athletes, regardless of specialty.

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Ok, after reading this, I am completely confused. I thought that anaerobic threshold and lactate threshold were basically the same thing and that the AT that Gordo describes is aerobic threshold which is significantly lower than lactate threshold. I’ve been working under the assumption that my lactate threshold and aerobic threshold are about 25-30 beats different.

I’m confused how they could be the same number when one is the so called “first opening of breath” and the other a number I can’t reach unless going very hard.

What Aet is Gordo talking about? Aerobic threshold, anaerobic threshold or ananerobic threshold? I’m completely lost now.

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What Aet is Gordo talking about? Aerobic threshold, anaerobic threshold or ananerobic threshold? I’m completely lost now.

At the risk of soundling glib – Gordo is talking about what Gordo is talking about. It’s not right or wrong. The point is that he defines a benchmark.

His favored benchmark is easy to find, easy to refer to, and is consistent “enough” for an athlete over the course of a season. It is “accurate without being precise.”

Gordo uses a ventilatory reference point for determining the following basic effort measure:

“OK! Now I’m working. This is where I start getting a training benefit.”

He has his crew work at certain levels above and below that point to get various training benefits. It’s the same as with all the other reference point training systems. This basic effort measure is at the core of all these various things. “When am I beginning to do some meaningful work?”

None of these reference systems are ideal. All involve some compromise.

LT (lactate test) is troublesome, because we can’t run around pricking our fingers; Anaerobic Threshold (as defined in the textbook excerpt above) is troublesome because we don’t own metabolic carts. The “original” Aerobic Threshold is pretty good since we can buy HR monitors cheap, and do a Conconi test on a Computrainer or treadmill, or even at the track.

Gordo’s “AeT” is very good because anybody can wear a HR monitor and go out and run and become self-aware. Some would argue it’s not precise enough, since HR varies so much. I think power/pace is the most precise, but you’ve gotta buy a Powertap or the like, and a pace meter like a Timex or Garmin GPS.

In sum: They’re all just ways of attempting to measure just how hard we are working. We can measure all these various “markers”:

Thing Measured – Common Paradigm Name

HR – Aerobic Threshold

Breathing Rate – Gordo’s AeT

Lactate – Lactate Threshold

Gas Exchange – Anaerobic Threshold

Power and Pace – Power/Pace Duration Curve

They all work, if used properly. I like Gordo’s AeT and the Power/Pace Duration systems the best.

31

The only thing that makes sense to me is that LT/AT/whatever you want to call it should be defined when the slope of lactate curve changes. 1 mmol over baseline seems a little arbitrary to me. What do you think?

Defining LT as a 1 mmol/L increase over baseline is arbitrary, but has been used by some because it is less subjective than trying to determine exactly where the slope changes. Only a handful of people actually use this definition, though.

To answer my own question re. Hellerman: a PubMed search reveals three papers, two original articles and one that appears to be a review in a clinical journal.

To complicate things even more, blood lactate clearance/buffering/usage is also not a constant. It also increases with exercise intensity, though not to the same extent and with a bit of a time lag.

Find that workload where blood lactate takes off non- linearly and hold that intensity and the curve will flatten again and blood lactate will tend to level out at some elevated level.

I’m convinced that due to these inaccuracies and day to day variability, complex metabolic testing is probably only of real value to scientists. For coaches and athletes, simple field tests are more than adequate. Seems that scientists not only can’t agree how to define ‘lactate threshold’, many say that the term is a misnomer. In real life, the pace or power output you can maintain for 30 minutes or an hour or whatever is what’s really important, no matter what name you give it.

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The “original” Aerobic Threshold is pretty good since we can buy HR monitors cheap, and do a Conconi test on a Computrainer or treadmill, or even at the track.

I think the Conconi test is used to estimate anaerobic threshold, not aerobic threshold.

Otherwise great list.

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Everytime a simple question like freestyle’s pops up in a group like this, a discussion like this always ensues.

The people with a physiology background start discussing the definitions of the metabolic thresholds and the heart of the question is lost. And that’s where exercise physiology departs from the real world of training… the same real world that they were supposed to study and help.

Even though all these discussions are very enlightening, the real world fact is that lactate testing works in the real world. Most people that say that this or that method of calculating the lactate threshold doesn’t work, is not accurate, etc, has never done any testing, only read the papers. The Conconi test? Yep, also works. Time-trials, races run as tests? Yep, they’re the best in fact!

For the coaches and athletes out there, the question is: How can I measure the intensity of the exercise I am performing in a practical and cost-effective way? And in order to do that, several practical tools are available that work.

The cost-effective part is also something important. Cost-effective doesn’t mean cheap. It means the best method of controlling intensity for the level of the athlete. It kind of bothers me when some coaches try to sell power training on the bike for age-group athletes, even real good ones. Or lactate testing. It’s simply a way to make a(nother) buck out of the sport.

Paulo

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“Everytime a simple question like freestyle’s pops up in a group like this, a discussion like this always ensues.”

Hey, it’s a lifestyle forum right? :wink:

Now how do you feel about gay marriage?

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I’m all for it, sad marriages are not that fun… (lame joke, I know)

Now those newbies really need to learn to ride before racing!

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Now those newbies really need to learn to ride before racing!

Especially those with clincher “race” wheels…