Critical Speed (N-Zone Topic)

  • Creator
  • #52743

    What is critical speed?

    Is critical speed important?

    How do I develop it?

    When should I develop it?

  • Participant
    Dada on #52746


    Thomas Summer, MD on #52814

    Hi Steve!

    good question. I actually don’t really use this term, but from what I understand it’s somewhat similar to AnT. So where lactate is still at a steady state. But critical speed is not only limited to lactate, but also other factors. So it might be pretty well represented with an AnT test in the field to determine HR at AnT.
    Please share your opinion, Steve! I think I have to do some reading about this topic, as the term is something you hear about regularly.


    russes011 on #52817

    Critical speed (CS) is one’s fastest speed (or pace) plotted against time. An example curve is attached below. As you go further out in time on the x-axis, the curve levels out–this is one’s critical speed, or in essence what your POTENTIAL ‘steady state’ is for for 30-60min.

    Performance at specific distances/times longer than 30-60min can be determined by a percentage of your critical speed: for example people who win marathons run the marathon at 95% CS, while those who take 4 hours to do a marathon run it at, say 75% of CS. Similar percentages can also be applied to ultramarathon race times. In essence, CS represents one’s endurance potential, and the closer you can run near CS–for a specific race time (distance)–the higher chance you’ll win. This metric can also be applied to FKTs.

    Lactate threshold, or AnT, may approximate critical speed but is usually different, or lower. This is because the definition of each is different, as well as the tests to determine them are different. The classic AnT test, for example, usually never reaches CS because most athletes, even highly trained ones, can’t maintain CS for an hour, let alone 30min. This is why tests to determine CS only take <20min, or even <5min. Lactate threshold is determined by a blood test, which appears to be routinely below CS.

    W’ (or ‘anaerobic work capacity’) is the amount of additional speed you can produce (for a specific work load, eg incline) above critical speed. This is a constant value for a specific CS, for example, when operating above CS you can either run up an incline at 10m/s for 1s or 1m/s for 10s or 5m/s for 2s, and that’s it–it’s up to you how you want to spend this set amount of work capacity.

    I’m curious how changing ones CS changes ones W’ and vice versa?

    CS is trainable and determines your endurance potential. I see it as analogous to max strength being trainable and determining you power potential. (Or maybe they are the same thing?) And if true, does this mean that CS and max strength together determine your ME potential?–with CS being more important for longer events or goals?

    You must be logged in to view attached files.
    russes011 on #52905

    What type of intervals improve critical speed?

    (As far as I can tell most folks use about 3min (max effort) for these intervals, usually in a 1:1 work:rest ratio? Is there a specific UA work-out that addresses this?)

    What type of intervals improve W’?

    (I presume 8-10s uphill sprints fall into this category?

    What type of intervals improve LT (LT2, AnT)?

    (I presume weighted hill carries fall into this category?)

    Does max strength (or speed) training increase critical speed, or just W’?

    I understand that all types of intervals improve all of the above–but would like to be more specific. My knowledge on the above answers is either limited or what I presume I know is a bit shakey.

    Note: Not quite sure where 30/30s fall into any of the above categories–but I’m assume it does somewhere. 30s is too short to fully achieve VO2 max, at least on flat terrain, or even on some steeper terrain when starting in Z1 (I think it takes about 30-40s to hit VO2max). On steep hills, without a full recovery between intervals this very likely is possible. That said, 30s may not be a long enough rest for your W’ to be recycled, thereby degrading the efficacy of truly training W’ and/or perhaps CS–that is, with repeated intervals your body may become too spent to perform any real work above CS. I guess the answer depends on what is a more efficient way to train CS: time spent above CS, or time near, but below CS? Any input appreciated.

    (Note2: I think in many circumstance CS can be defined as vVO2max or the velocity at VO2max–but I think this is an oversimplification. For the point of this discussion we can make VO2max and CS interchangeable).


    russes011 on #52911

    On further thought maybe 30/30s function more to increase your LT (AnT) and make it become closer to CS (VO2max), and not to target VO2max per se. (Granted VO2max should have a benefit from any type of training, including 30/30s, but perhaps not as much as if the intervals include work above CS or VO2max.) Perhaps then 30/30s should be classified more as an LT type of workout because you are training between CS (VO2max) and LT, and closer to LT with time–in essence the more global 8-10min 30/30 interval block functions as a long LT type interval.

    Dada on #52919

    Steve, maybe this helps you with the question how to improve vVO2max:

    And 30/30s are good for Vo2max when you keep the “resting” 30s still very intense. That is why the famous 30/15s go for just 15s of rest so the athlete can reach Vo2max areas quicker and time at intensity is high. This is excellent Vo2max training.

    russes011 on #52926

    Dada–thanks for the link and post.

    I listened to the podcast and read the review article from 2007 it summarizes. My take home point from reading it is that we don’t really don’t know what is ‘best’ to improve VO2max–training at, below, or above. The data seems conflicting, at least from 2007. I have no doubt that 30/30 improve ones VO2max, but I was uncertain if it was the most efficient approach. I suppose the point is moot, or that we don’t really know whether it’s more efficient, especially since many think as you approach VO2max, the different training responses to different types of intensities and intervals probably just gets blurred anyway. One thing that seems pretty consistent though is that ‘hard’ training is probably required to improve VO2max once one has an aerobic base. Also, VO2max requires laboratory testing to determine–so it’s kind-of useless as a marker of progression or metric to follow. Even LT2 or AnT is also not so reliable a marker to follow either, due to the relative subjectivity of the test, and the somewhat difficult nature of this pace to pinpoint with say 10-20min training intervals. Hence the topic of CP. I don’t know but maybe CP may eventually become the most useful metric for higher intensity training.

Viewing 7 replies - 1 through 7 (of 7 total)
  • You must be logged in to reply to this topic.