If found in litterature loads of papers challenging the concept of AT ( Anaerobic Threshold ). Most of them explain how this is only a construct and how and why previous expert were lead into believing that there is a POINT where metabolism shifts.

Who can explain me better this topic and possibly clarify if in the scientific realm has finally someone drawn a endpoint to this?

  • The problem is that you are considering AT in situ, rather than as part of a system. AT will move even in an individual, as the body responds to training by more efficiently using and/or flushing out lactate. I would personally rate AT as a concept, since it is a proven thing. AT or LT is that point in an individual when lactate accumulates faster than it can be cleared. That's an accepted fact. The debate rises in being able to predict it, and what affects it, and using that to predict performance. (Much like VO2max which is a poor indicator of performance, but a great indicator of potential)
    – JohnP
    Commented Feb 6, 2017 at 20:52
  • The debate is whether there is a firm point of flexion in the v-slope graph, or - as for example Timothy Noakes Dr. states - there is not, but just an exponential increase. I think the core of this misundestanding is that some researchers still reject the role of lactate as a metabolism intermediate instead as the culprit of lactic acidosis. I've read the 2009 paper on Sport Medicine about AT concepts but I still have my reserves because they've been very picky with the review. The point where lactate is accumulated is a fact, nothing to say about it: the problem is HOW it is done as a system.
    – Liv
    Commented Feb 7, 2017 at 5:46
  • I'm not a solid fan of Noakes, personally. But agreed, the system as a whole needs much further study.
    – JohnP
    Commented Feb 8, 2017 at 7:20

1 Answer 1


The most basic definition of the Anaerobic Threshold is where the body generates more lactic acid than it can flush out. So if you were to make a line graph in which one line represents the rate lactic acid increase and the other line represents the rate of lactic acid decrease, the point at which the lines cross would technically be the "anaerobic threshold". Lactic acid builds up faster as the intensity of a workout increases. The rate at which it's disposed of is relatively constant.

Sprinters can train above this point without much issue because their running is in very short bursts. Endurance athletes though need to stay below this point in order to continue on without having to stop for rest. You can, however, improve your ability to remove lactic acid through consistent training. As such, the speeds, distances, and times would increase.

I think the "metabolic shift" part comes from where people are told that at a certain intensity, your body starts generating energy through anaerobic (no oxygen) means rather than aerobic (oxygen). When you're aerobic, you generate energy by using fat whereas you would use glucose if you're in the anaerobic phase. The idea being that you would burn more fat if you stayed within this aerobic center. You'll often see charts on cardio machines that say "aerobic between 60% to 70% of VO2max" or something.

This is a general over-simplification of how the body generates energy. What the body chooses as a source of energy is far, far more complex than that. It is based off a large number of factors. Also, the body is using both systems for energy pretty much all the time. You are in fact using both energy systems right now reading this while at rest (I assume you're at rest).

The body will start using more of its anaerobic energy system as a workout increases in intensity because it needs that extra energy to perform its duties. It will, however, never stop using the aerobic system.

  • I'm well aware of these notions. My question is different, and you missed it in toto. Anaerobic Threshold concept has been challenged in the last 20 years, and now more than ever. What you pointed out are just basic physiology and biochemistry info that I know well. My question was to clarify the topic of the debate between the two sides ( AT supporters and debunkers ), not the "AT topic".
    – Liv
    Commented Feb 5, 2017 at 11:52
  • Then maybe I was confused on what you were asking. People used to think there was a "metabolic shift" when you crossed the AT because you suddenly see this dramatic increase in CO2 in the bloodstream. So the conclusion was that you aren't using the anaerobic system until you hit this point. Now, we know that the increase is only because the lactic acid isn't being drained, so if course you'll see this sharp increase.
    – DeeV
    Commented Feb 5, 2017 at 18:12
  • The increase is due to H+ ions pumped along with LACTATE ( not lactic acid, that is different ) through lactate shuttles. There is still this misconception of the whole glycolysis being just Glucose -> Lactate + H+
    – Liv
    Commented Feb 8, 2017 at 8:38

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