Dr. Phil Maffetone & Alan Couzens: Pros and Cons of Metabolic Testing, Plus: MAF Q&A

February 22, 2016


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On this show we’re joined by Dr. Phil Maffetone and endurance coach Alan Couzens!

Part 1: MAF listener questions

  • For an experienced master’s marathoner (age 53), is 172 average heart rate too high for a marathon?
  • MAF pace slowed down significantly after completing the Two-Week Test. Why would this be and how to get it back?

Part 2: Metabolic testing in a lab

Value to the athlete:

  • Performance: Strong link between fat oxidation and Ironman performance. Equal correlation to OBLA (FTP). Especially so at higher end of performance/for larger athletes.
  • CHO stores 2000-3000kcal Competitive Ironman = 8,000-9,000kcal output for avg size athlete.
  • We have to make up the balance or intensity will come down.
  • Health: Almost all the ‘big hitter’ diseases are related to poor metabolic fitness: diabetes, but also CVD, cancer, Alzheimers have been linked to metabolic dysfunction i.e. messed up hormonal response (IR) AND mitochondrial dysfunction. Graded metabolic test hits both.
  • Bottom line — with all of the possible numbers out there for an athlete to track, this one offers HUGE benefit to both your performance & your health

Key concerns:

  • Metabolic testing is a poor business model for a lab.
  • ~6hrs per test with set up, long test, analysis, clean up.
  • A good quality met cart is north of $20,000.
  • Therefore, lots of folks cut corners in both time (shortening of stages, start at too high intensity, omit warm up) & equipment (cheap metcarts).


  • Go to a college or hospital. They can afford good met carts and are less time conscious/more apt to experiment.
  • Go with your own protocol. Most colleges are VO2max focused & are less familiar with longer protocols.
  • Fast 3hrs prior
  • 30 min w/up VERY easy. (can be before test e.g. easy commute spin)
  • long test ~10x5min stages. Takes a while for RER to stabilize at each stage.
  • from <AeT to max. (e.g. 150-350W 20W steps).

What you want to see:

  • Tall AND broad fat oxidation, i.e. you have a high level of fat oxidation and you burn it at a wide range of intensities.
  • Large/top male pros: 7-10kcal/min (> 70% VO2max/20kcal/min)
  • Top level age-group male: 4-6kcal/min (->15kcal/min)
  • Top AG female: 3-5kcal/min (->10kcal/min)
  • Most <3kcal/min with drop off starting @ 60% VO2max
  • Keto up to 14kcal/min – high but not broad.

How to utilize & improve results:

  • Nutrition AND aerobic base work (in equal measure!)
  • What kind of diet?
  • Sports nutrition
  • and more!

Comments (5)

  • JoeyHinton says:

    Great podcast!!! Heaps of good info.

  • IronMattBach says:

    Very interesting discussion on this topic! It would be nice to have a listing somewhere of people or locations where you can get a metabolic efficiency test done. For anyone in the NYC area, I've been working with Nicci Schock of Elevate By Nicci on the nutritional piece and on testing. She has one of the $20k+ metabolic carts and does an excellent job with the protocol (closely matches what Dr Maffetone and Couzens were talking about on the podcast)

  • Joe Pope says:

    Do you have any recommended labs to use in the SoCal area?

  • SockPuppetPedro says:

    Loved this episode to the point of wanting to go get a metabolic efficiency test done. But I'm slightly confused about potential outcomes. For example, what if my crossover point is somewhat faster than my MAF pace? In that instance, what makes sense for my training pace?

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