Searching For The Cardio Code

One of my fitness mentors is Chris Highcock from Conditioning Research and author of Hillfit. He always seems to be a year or two ahead of me when it comes to fitness interests and knowledge.

In a comment recently, he referenced a book called The Cardio Code that makes the case for why the science is clear that cardio is necessary for heart health and that lifting weights or even lifting weights in an interval setting is not enough. If anyone else had posted the link, I would have dismissed it and moved on, but it was Chris, so I fired up Bing and did a search.

The Cardio Code was released in 2014, but unfortunately only as an iBook on Apple iTunes. No paper. No Kindle. I dusted off my version 1 of the iPad only to discover I can’t update to the latest iOS version in order to read the book. And since I use Windows and not Mac, I can’t read the book on my laptop. I really do not want to have to read a 270-page technical book on my iPhone.

Now there may be a way to buy the book and convert it to a Kindle-friendly format, but every time I’ve done that in the past, the formatting has been a disaster.

Why wouldn’t the author put the book up on Amazon? There are services to handle both the conversion to Kindle and print-on-demand.

I discovered the author’s website, which to be kind is “a piece of crap”. More embarrassing than McGuff’s Body By Science site before the “Chinese hackers” got to it. 🙄 Sorry, I’m a little opinionated on this topic. See The Digital Graveyard of My Health and Fitness Mentors for details.

I located a January 2017 podcast interview with Dr. Kenneth Jay on Leo Training. You can hear that here. The cardio portion of the interview starts around 19 minutes. Although his publishing strategy and website are terrible, his arguments impressed me.

My bias against cardio took a serious blow. Now perhaps someone in the HIT community far smarter than me can find flaws or disagreements with Dr. Jay, but I couldn’t. I still want to read the book or something to better understand this topic, but I’m not buying a new iPad to make that happen.

Not giving up, I went to the Wayback Machine and found an earlier version of the Cardio Code website. A much better version too!

Some highlights from this page:

  • Cardio is defined as exercise or training to make your heart work better.
  • The goal is to improve the pumping- and blood delivery capacity of the heart to the working muscles.
  • The best stimulus to your cardiovascular system is when is when you DO NOT limit blood flow back to the heart.

Why not just lift weights faster?

The problem arises with the muscular tension used to lift the weight. Because blood delivery to the working muscles depends heavily on perfusion of the muscle (meaning: can the blood actually get to the muscles that need it?) the oxygen rich blood has a hard time getting into the contracting muscle as it (the muscle, that is) will squeeze the blood vessels shut. The vessels may not close completely (that depends on duration and intensity of the contraction) but the blood will have a harder time getting to where it is needed. This is of course a major problem, which will increase heart rate in an attempt to force blood into the muscles. Unfortunately, the net result is only a large increase in blood pressure and a limited return of blood to the heart.

The rest of the blog post discusses VO2Max, intensity, and sports variations.

Right or Wrong? Undervalued or Overvalued?

As a once hardcode cardio skeptic, do I think Dr. Jay is correct? Likely, but for me, that is the wrong question to ask. He is smarter than me as are some of my fellow cardio critics. The way I am approaching this question is as an investor.

For at least a decade, I have heavily invested in the cardio is crap exercise portfolio. I achieved tremendous gains using HIT and walking, but it appears to be time to rebalance my portfolio. Cardio is undervalued to me at this time. It is worth pursuing.

I’d still like to read the book, but that may not be possible. In the meantime, I will ease into some cardio. What type? That will be the topic of my next post.

me on a bike

Time to dust off my old bike? 🤣

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Critical MAS is the blog for Michael Allen Smith of Seattle, Washington. My interests include traditional food, fitness, economics, and web development.

13 thoughts on “Searching For The Cardio Code”

  1. I’ve always gone back back to Bill Phillip’s Body for Life workout where he combines weights and cardio. I’ve found I feel and look my best following his simple but challenging program.

  2. MAS,

    Many threads ago, I tried to discuss cardio right here. No interest. Ditto Dr Darden and Corporate Warrior. HiTers hate the word cardio and are opposed to any type of cardio exercise. I lost interest in this site due to that lack of interest in cardiovascular conditioning.

    I have Dr Kenneth Jay’s book and it is indeed rich with information. Dr Phil Maffetone is a great source also.
    “Turn Up Your Fat Burn” Alyssa Shaffer is a great start read and discusses the important Ventilatory Threshold 1.
    Further study (free) of the Krebs cycle is important.

    A little amount of study will convince all objective persons that Dr McGuff’s Global Metabolic Conditioning is false reasoning.

  3. @Marc – Like others, you were ahead on me on this topic.

    I typically have a single primary fitness interest at any given time. Back in April when you commented on Dr. Jay, I was at the height of my frustration with my knee injury. A month later things would begin to improve, but at that time, the idea of cardio was the last thing on my mind.

    I’ll follow up on your reading recommendations. Thank you!


    “In a series of recent studies, we have defined the exercise intensity at which maximal fat oxidation is observed, called ‘Fatmax’. In a group of trained individuals it was found that exercise at moderate intensity (62-63% of VO2max or 70-75% of HRmax) was the optimal intensity for fat oxidation, whereas it was around 50% of VO2max for less trained individuals.”


    The talk test comes in handy … in other words, when cardiovascular exercise become strenuous and starts recruiting more muscle mass, more oxygen is needed to spin the Kreb’s cycle to make more ATP for energy. Labored breathing means you are now using the anaerobic and the aerobic energy pathways simultaneously as your lungs and CV can’t keep up with O2 demands. The Kreb’s cycle must replenish the anaerobic stores also.

    Cardio refers to the heart.
    Vascular refers to the blood supply network of the body
    The lungs decline significantly as we age …
    What can one do to counteract that?

  5. Actually , the above is wrong … The Kreb’s cycle must replenish the anaerobic stores also … as anaerobic glycolysis does not require oxygen and uses the energy contained in glucose for the formation of ATP and uses a different mechanism to replenish.

  6. If you think about the various systems of the body, and which are rate limiting to health, it makes sense to build up the aerobic system in order to increase the rate and efficiency of its various processes. My reading indicates that it is the aerobic system that replenishes the anaerobic system trained with weights. Therefore, improving one’s aerobic capacity would enhance one’s ability to recover from intense physical effort.

    Resources I have seen that seem at least more knowledgable than most about how to develop those systems include Phil Maffetone (mentioned above) and Brian Mackenzie ( who focuses on nasal breathing. Other important resources on breathing are books on Buteyko breathing as well as the Oxygen Advantage by Patrick McKeown. What is generally under-appreciated is the role of carbon dioxide in breathing, and its role in oxygen uptake. Having the ability to tolerate greater carbon dioxide in the body helps with aerobic efficiency because it allows for more efficient oxygen update per breath.

    What I don’t enjoy about aerobic development (and I suspect is the case for many) is that it seems to require long stretches of exercise at sub-maximal efforts, which don’t get the endorphins pumping. Additionally, hypoxic exercise can be quite stressful also without the endorphins I find.

    I haven’t found a shortcut in any of the above, but I do think that combining Maffetone (focus on heart rate and fueling) and Mackenzie (focus on developing oxygen update efficiency) would help to accelerate that development.

  7. @Brock – Thanks for the resources. I just heard an interview with Brian Mackenzie last week, so all this info is coming my way now.

  8. I was wondering how long it would take for Clarence Bass to come up in the comments. He’s been using resistance training and aerobics for years.

    In fairness, though, the popular views of McGuff and Maffetone are a little oversimplified. I never read McGuff as saying – don’t do aerobics. Wasn’t one point in BBS that aerobics didn’t qualify as “exercise” under his rigorous definition of the word? Aerobics for McGuff (who road BMX as I recall), was activity, not exercise. Likewise, Maffetone doesn’t eschew all anaerobic exercise (again using his rigorous definition of “aerobic”). His point was that aerobic development needed to precede anaerobic training and that anaerobic training should never come at the sacrifice of aerobic work.

    That Wayback Machine post from Dr. Jay has a big focus on VO2 Max makes it sound as though intervals are in your future, MAS. Will we be seeing HIT meet HIIT?

  9. @Geoff – In that podcast interview, I recall Dr. Jay pushing for low-intensity aerobic conditioning and not HIIT.

    My plan is to build that aerobic base first, which I suspect will take a while and use what I learn to decide my next conditioning move.

    How I build that base is still unknown and will the topic of my next post.

  10. Brian Mackenzie is associated with CrossFit Endurance and the book Unbreakable Runner, a program that promised success in ultra-endurance events with only small amounts of specific training, carried out at high intensity and supplemented with CrossFit workouts. He made some bold claims about placing in running ultra-marathons but, unsurprisingly, failed to deliver. In the ultra-running community he is considered something of a joke.

  11. @Mark – Thanks. This topic and landscape are going to be mostly new to me. I’ll need to filter their message and their intended audience with my needs.

    For the most part, I won’t know the good guys from the less-than-good, but if I test the ideas that interest me properly, I might be OK.

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