Can my gas exchange test give me an AeT ballpark?

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  • #23779

    Age: 63
    Sex: Male
    Diet: Some form of low-carb for decades, not specifically for athletic performance but because I feel better eating that way. For the four weeks prior to the test my daily dietary intake averaged: 3042 kcal, 131g protein, 16g CHO, 274g fat. In percentage terms 18% of calories were from protein and 80% from fat.
    Goal: Thru-hike the Appalachian Trail April 2021
    Background: About three months ago I started reading Maffetone, thinking he would be helpful for my brother who just finished his first marathon. Then a little light bulb went off and I thought, maybe I am an endurance athlete too because I do things like backpack for two weeks on the Long Trail in Vermont (link takes you to a shout-out to Uphill Athlete from the holder of a new FKT.

    So, about two months ago, I decided to follow Maffetone. I stopped all strength training and tried my best to always keep my HR below 108 bpm (180 minus age minus 10 for gout medication).

    The biggest problem I had was that I was waking with baby steps and stopping uphill and then running downhill on rocky, wet, and muddy trails. For someone like me, with a problematic left knee, I knew this was not smart. But Maffetone stressed the importance of staying within 97-107 bpm, so I would speed up on descents.

    About one month into Maffetone, someone told me to look into Uphill Athlete, so I read TFTNA AND TFTUA, and it was if the scales fell from my eyes and a whole new world opened up to me. But before I could develop an Uphill Athlete plan, while I was still doing the Maffetone Method, I messed up my knee going too fast downhill on a rocky trail, trying to keep my HR in range.

    About 7 or 8 months ago, I reached a HR of 178 on an elliptical machine (I think I got that high with my mouth closed the entire time). So, I assume that that is close to my HRmax. it should be noted that for almost two years I have only done nose-breathing when training. The only time I have done mouth-breathing is when hiking with others going fast on ascents or, two days ago, when I did my metabolic efficiency test.

    My Metabolic Efficiency test operator was certified by Bob Seebohar.

    I am attaching the Crossover and Fatmax reports.

    My results seem similar to those discussed by member allisongillespie here.

    If you look at my reports, my MEP crossover point is rather high relative to my capacity yet I think it is occurring at a rather low level of performance: 18:10 min/mile at 15% incline and 15:23 at 11%. That would suggest ADS to me.

    I have not yet done an AnT test and have no idea what speed and incline to start with on a treadmill. I doubt I could maintain 164-167–my supposed MEP–for half an hour, but I haven’t tried.

    But, to get started, I am not that concerned for now with my AnT. What I would like help with is understanding where the top of Z2 is. Fatmax is 145 bpm but even that seems high to me, especially since it would be laughable to consider me an elite athlete. (I regret not taking a photo of the computer monitor when the test was done, since the tech didn’t know how to export the raw data that I asked for. I eyeballed the fat g/minute column and my highest momentary reading was 0.92. I was really hoping to hit 1.0, but what really counts for me is performance on the trail, not my lab values.)

    I walked about 15 minutes before I entered the metabolic testing facility. I then had a 15-minute warm-up at 0% and 18:10 min/mile, with subsequent 5-minute stages. The test occurred around 7:15 am, I was fasted. I did not exercise the day prior to the test, other than a couple of “stir the pot” reps on a swiss ball around 7 am, before I remembered that all exercise was strictly verboten.

    To reiterate, do these tests give me sufficient information to determine my AeT, and, if so, at what HR is my AeT?

    (Note: I do not have a lactate meter but did take the following readings:
    Blood glucose: 90 mg/dl pretest, 139 mg/dl posttest
    Beta-hydroxybutryrate (ketones) 1.1 mmol/L, 0.8
    Uric acid 4.3 mmol/L, 14.8)

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    Anonymous on #23810

    What this test showed is that you are a very well fat adapted athlete. The MAF numbers you mention suggest you are 62 years old. It you are sure the max HR you saw was accurate (collected with a chest strap monitor) then you have a very high HR for someone your age. In my experience the MAF method will typically err on the conservative side in finding your AeT HR. I understand his idea and over a whole population the 180-age formula may give a decent idea of average AeT HR. But there is a great deal of interpersonal variability in HR response to exercise. At 65 my max HR is now about 168. That’s why we prefer to do some sort of individual test like the one you did or on described here.

    These tests show your personal response and do not rely on formulas. Normally I would call the top of Z2 (the AeT) the HR you reached at cross over or RER=.85. In your case that is 165 and my gut tells me that is too high to sustain for hours. So, I recommend you do the HR Drift test described in the link above. This is a performance based test not a lab snap shot. Another good verification that you are training below AeT is that you can get up tomorrow and do the same workout you did today. You will recover in 24 hours.


    Participant on #23816

    f you look at my reports, my MEP crossover point is rather high relative to my capacity yet I think it is occurring at a rather low level of performance: 18:10 min/mile at 15% incline and 15:23 at 11%. That would suggest ADS to me.

    Is that such a terrible performance? The paces and inclines are equal to climb rates of approx. 800 and 700 meter per hour.

    I am not exactly sure what is considered a good climb rate at AeT, but I certainly wouldn’t be able to do 800 meter per hour without exceeding my AeT.

    (I guess you are nido from the RA forums, btw? I am Allan Olesen.)

    depeyster on #23836


    Thanks for the help! I will start doing the AeT test on a treadmill.

    Also thank you for the books, which have opened up a new way of viewing the world for me. Not only was I blown away by the advice it contained, but it was beautifully composed making it a pleasure to read multiple times.


    Yes, you are the person who turned me on to this site. Thank you! I suppose the drive for self-improvement is what brings us here. As I alluded to in my first post and as Scott tentatively confirmed, I very much doubt that my AeT is within 10% of my HRmax. I don’t know if I could even keep up at my MEP for 30 minutes, let alone 60 minutes without HR drift.

    Anonymous on #23964

    Hey Just curious, what are the “RA forums”?

    depeyster on #23992

    Hey Scott. Allan was referring to I am not a runner but I decided to read a Maffetone book because I thought it might be relevant to my thru-hiking ambitions. In Maffetone’s book he mentions So, I went there, explained my interests, and Allan pointed me over here, along with giving me lots of other great insights.

    Anonymous on #23995

    Cool, thanks. I hadn’t heard of RA. I’ll check it out.

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