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!