Monday Musings: Marathons and Heart Damage

This post is the first in what may become a new series here on MDA. Most of my articles are full-length feature articles. While I love and will continue to do them I think there’s room for a post each week that’s a little less formal; something shorter than my usual fare that’s published each Monday (along with the WOW) that allows me to spout off on any number of things on my mind. I’ll likely be reviewing the latest medical research and ranting on hot topics in the news. What do you think? Would you like a hodgepodge collection of my thoughts on the world of health and fitness? I hope so, because I’ve got a lot to say! Let me know what you think in the comment board. And now… the inaugural Monday Musing…

Marathon running is supposed to be good for you, which is why so many people (intend to) do it. The overweight and the untrained often use the successful completion of one as a landmark on their weight loss journey, sometimes the goal itself. Others think, erroneously, that it’s part of an anti-aging strategy. If you can run a marathon, you are fit, or so the story goes.

New MRI data out of the Heart and Stroke Foundation suggests the contrary: that “less fit” runners running a marathon are damaging their hearts for up to three months. The musculature of the human heart is made up of 17 segments. If one segment fails due to stress (say, from a marathon), adjacent segments pick up the slack. Unfit marathoners exhibited abnormally high amounts of overly stressed heart segments. Their hearts were working harder, and the work was concentrated across fewer segments. These abnormalities persisted for as long as three months after the marathon.

Okay, exercise induces muscle damage as a rule. That’s how we get stronger – by undergoing stress and muscle damage, and adapting to it by rebuilding our muscles stronger than ever. But muscle damage isn’t supposed to last for three months. Sure, even the study’s authors admit that the damage is reversible, but is that really an effective way to train?

The problem is that there’s no built-in shut down code in our central nervous system when it comes to running a marathon. The heart muscle doesn’t sense the “pain” of exertion the way leg muscles do. It just tries to keep up with the demand to pump more oxygen. Total beginners with a new pair of $150 Nikes (with shock absorbers, stabilizers and motion control) and a fanny pack full of glucose gel can sign up for a marathon and (just) do it. It’s not so traumatic an ordeal to trigger an automatic response; it’s more drawn out and gradual a muscle stressor.

Beginners should probably not be running marathons. Truth is, I don’t even think experienced endurance athletes should be running marathons as often as some do (I keep tabs on all my old elite runner/triathlete friends who have had serious heart problems – or died – and it’s at a significant number now). But good luck getting that across. They – we – can be a stubborn bunch. If you want to get fit and you’re starting from scratch, lifting heavy things, engaging in slow steady movement often, and getting your diet in order are the most reliable, safest steps toward that goal. Running a marathon sounds badass and impressive, but remember – the first marathoner dropped dead after completing it. Myth? Maybe, but I wouldn’t take it lightly. If you insist on doing one, please train properly.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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83 thoughts on “Monday Musings: Marathons and Heart Damage”

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  1. I wonder what their definition of “less fit” is? Let’s see… looks like they tested V02 max, though it doesn’t say what the cutoff was. (though that hardly matters to me beyond intellectual curiosity — I have no marathoning planned for the next several evers of my life.)

  2. Mark –

    Interesting concept. The full length articles have been great, but I think shorter pieces like this can serve a great purpose as short reminders about the simple truths behind the Primal Blueprint.

    Quick question about marathoning (from a recovering endurance athlete) – how do you feel about training for – and running – a marathon or ultra endurance event in the “move slowly” zone? Of course there would be a couple of “lift heavy” sessions each week and some regular sprinting to round out the primal fitness, but what about doing the vast bulk of the running training in that lower heart rate zone? I’m thinking something akin to the type of training espoused by Phil Maffetone here rather than the typical “chronic cardio” stuff. If one could go the 26.2 at a reasonable clip at < 75% of max HR would the dangers of the distance be at least somewhat mitigated?

    1. I don’t think, aside from sprinting, that I ever run at more than 75%. Probably significantly less, although I have no intention of using a heart monitor. The whole point of distance running is long and slow. I think most marathon injuries are from just bad running (and diet, and poor training, and bad shoes, bad all sorts of stuff).

  3. Yes, random thoughts are often the most interesting cream of the crop gleans from the morass of information that you surely process day to day. Please share!

  4. I’d be glad to see some more short posts about random stuff that isn’t necessarily preaching the primal lifestyle. I’ve read a lot of your old blog posts aswell, and studies on sleep quality when wearing socks or not are fun to read imo!

    1. i think preaching the primal lifestyle is a main thrust of the blog? …i like such posts, they keep me inspired

  5. Well, I have been thinking a lot about this lately. Back before I started to adopt the Primal lifestyle I signed up for a 1/2 marathon which is scheduled to be run this weekend. So I am wondering how to approach it.

    The way I see it I have the following options:
    1. Skip it and be out $70
    2. Run it
    3. Approach it as a Grok-a-thon. … Sprint, jog, walk etc. and just enjoy it. Maybe do a little persistence hunting?

    I’ve tried and change my approach to this. I’ve done a lot of low heart rate training and sprints follow Mark’s philosophy (Make easy runs longer and easier and fast runs harder, shorter and fewer.)

    My original goal for this was to complete in ~1:50 but know I think I just want to go and enjoy the exercise and being outside.

    Does anyone out there have any advice to offer as to how to approach this 13.1 miles?

    1. Grok-a-thon all the way! Just go out there and have fun…for me I love the excitement of races even though I ALWAYS finish last (or nearly last) in my age group…but no worries, it’s just a good fun time especially without the pressure of performance.

      1. I vote Grok-a-thon! At very least walk through the water stops and sprint at the finish to run down your prey (a runner you can see that you want to beat)!
        Years ago when I did a marathon with a friend this was our approach. Of course that was just because we could never get the water from the cup in our mouths successfully!

    2. Go and enjoy, keep the pace slow, it’s way more fun amongst the guys at the back, far more inspiring, and once you’ve done it, pat yourself on the back and don’t sign up for any more 🙂

      Cavegirl, retired endurance athlete!

      Mark – musings are the way to go, fill your boots, as your Aussie readers would say!

    3. Grok-a-thon all the way! Skipping it is a BAD idea. Just go out there and have some fun! Run with an older gentlemen in the back. Start off running and then walk for a while. Then sprint for a minute, etc.

      Go barefoot or wear your vibrams!

      1. In my experience, the older gentlemen do very well. And older ladies too. They probably have been running a long time and have the technique perfected.

    4. Absolutely enjoy. I’ve done the Seattle Half-Marathon twice. The first time I trained and did a run/walk. The second time I didn’t even train, was going to skip it, but my Seattle friends convinced me to go. I walked the whole route, and had a great time. Of course, the weather was much better than the first time.

      I say have a good time and do it the Grok way.

    5. FWIW, you’re out the $70 either way, so don’t let that factor into your decision. No point in wasting your time and/or harming your body, too.

      1. Walking is never a waste of time. Enjoy your surroundings and the people. These events are encouraging. In fact, start at the very back and encourage others. You will have done your good deed for the day.

    6. i LOVE everyone’s suggestions!! I’m signed up to do a half in Feb. I wasn’t gonna take it too seriously 🙂 I’m just going to be in FL in the dead of winter (for some VIT D) & hang out with my sister. I’m gonna grok mine too…

      1. Thanks for the suggestions everyone! All are great ideas. I think I am just going to do this the Tao way (we wei). Just go with the flow. I’ll run how I feel with no specific goal in mind, just make it to the finish and enjoy the journey.

    7. I’m training to walk a half right now. It’s been a little harder than I thought. I’m a slow walker, runner, reader – you name it. So I don’t have to pressure myself to take it easy. In fact, my main worry is that I’ll take 4 hours to finish! In terms of training – I’m relying on podcasts to keep me from getting bored – not to mention chatting on the phone. Every once in a while I get bored and jog for a minute or two. I haven’t lost a pound, but I love what it’s doing for my legs!

  6. While not elite in any sense, I was on the path of steadily increasing marathon training, with steady lean mass and upper body strength loss along with it. The winners of the races I entered were so thin, it was painful to look at their pictures in the paper the next day. One 10K winner was 5’6″, 104lbs. A man.

    At one point I desired to waste away to be more competitive. Thankfully CrossFit and then Mark helped convince me that was not optimum health. I am now 10lbs heavier, much stronger, with 2% LESS body fat than when I was beginning to feel emaciated from running.

    Now how do I convince my friend to slow down, who started doing this with me and pushed it much further, now training for his first full Ironman, after recovering from a recent stress fracture.

  7. All due respect, I don’t believe a word the Heart and Stroke Foundation says.If we listened to them, we’d all be (almost) vegetarians.

    1. but just think of all the “healthy” whole grains we could be eating!

  8. I’m also curious about more primal friendly training plans for a 10K or a half. I’m considering doing Jeff Galloway’s run/walk program. While obviously not primal, it seems to be a much less intensive approach, and with the planned, frequent walk breaks, you aren’t maintaining a long-term heart rate elevation.

    1. I had a friend run the marathon last year using the Galloway method.

      I think the method needs to be followed very closely – many people think that they can use the method to train less than they really need to in order to complete a marathon.

  9. Mark,

    I definitely like the idea of this occasional shorter article.

    One thing I’ve been wondering about lately and haven’t put enough time/effort/energy into is whether some of the genetic predisposition stuff is really that, or just similarities in lifestyles, particularly nutrition. Like, say my dad had 3 heart attacks, or high cholesterol, my dr might tell me I’m genetically pre-disposed to that. Am I really? Or is it likely that because my dad raised me I’ve probably taken on his lifestyle habits that led to said maladies? Anyway, if you’ve already covered this and I missed it my apologies, but wanted to throw it out there since my musings are never as eloquent as yours

  10. Love the idea of shorter posts, love the lengthy ones too….. how about just keeping ’em mixed-up…. I apprecaite all that you write Mark as your passion just shines through.

    Thank you!

  11. I remember reading about Derek Clayton who ran 2.08 for the marathon in 1969,a revolutionary time then.He suffered for months after.
    However the Kenyans with their background of running to school from the age of 5 seem to bounce along through a marathon.

  12. Mark,

    What I’d like to know (and probably never will) is: how many of your “elite runner/triathlete friends who have had serious heart problems”, have such problems due to the effects of performance-enhancing drugs?

    Seriously, have there been any legitimate studies on the topic?

  13. Yes, I like the idea of you spilling your random thoughts on fitness. Carry on, sir!

  14. I am a Greek who use to live by Marathonas road and I have no ambition to run it in this life or my next one! By the way that’s what I know too that Pheidipides dropped dead in the end

  15. Mark, what would you say if I plan to do a trail race of more than a marathon-length? I mean, that is very primal. But how to train for it?

  16. I must say that I would love a short post or 2 throughout the week. Random ones with your thoughts on different topics within the health world. While I enjoy reading your longer articles some of them are… VERY long!

  17. I love hearing this info from a former serious distance competitor. Thank you for giving me permission to stick with short distance and enjoyable exercise!

  18. Al Sears writes about this in his book PACE training. He says that sustained moderate endurance activities teach our hearts and lungs to become smaller and more efficient rather than stronger and larger when we do intermittent activity with intensity. Ya know, the way Grok woulda’ done it!

    1. I just watched a video about PACE. I like the way he said…”you wouldn’t curl a 1/2 pound dumbbell 10,000 times to build your biceps….this is what running distances is”. My brother tried getting me into running around the same time I started understanding the paleo lifestyle. Now I go out and sprint about 3 times a week.

  19. oh yeah. I’ll take some random thoughts. I think this is a good idea.
    Random thoughts on fitness is a bottomless well. There’s so many “fitness experts” out there selling their ideas. I’d love to hear what you think about some of them.

  20. I’ve wondered about Kenyans and the Hunter Gather societies that hunt for hours on end with running down their prey. I don’t think you would see some of them running 8 hours that often, only when it’s necessary to kill a good chunk of meat.

    I would like to do a marathon but I know it’s out of the question with my current work schedule (7 day work week).

  21. I disagree with your perception that CW thinks running marathons is healthy. In fact, I’d say the majority of the population thinks it’s bad for you. They’d cite “it’s bad for your joints!” as a reason it’s unhealthy.

    Furthermore, a lot of age group (and certainly elite) marathoners KNOW moderation would be better for their health.

    I think the general public aspires to marathon running because it’s a long way to run and most people don’t like running. I don’t think it’s seen as a standard of health. I will agree that fat too many people use it as a goal when they pick up running, like it, and get overzealous. More power to them for getting in shape but picking a marathon to run isn’t the best way to go about it.

    1. I cringed when Kat Von D decided to do a marathon to “get in shape” recently. She’s since decided to do it as a relay, but that wasn’t the initial plan.

      People DO think it’s healthy to strive for running a marathon. They train for it because it’s PROVING that they are fit.

      Unfortunately, along the way, they get addicted to the feeling of running.

      Another issue is that there are few “group” events that you can train for. People join running clubs, run together, train together, and have measurable and comparable results together. Many other sports SEEM to take more skill than running.

      The truth is that you should be fit to safely run long distances, not run long distances to be fit.

  22. I like the idea of posting shorter thoughts on numerous topics throughout the week.

    Regarding the running topic: While I am not fully following a primal lifestyle, I am trying to shift my dietary habits and exercise routines. Thanks to following P90X and Insanity programs, I have become a relatively fit person. I think they both are overkill as far duration.

    Recently, a friend talked me into running a 5K. I know this is not a big deal for a lot of people, but it was for me. Considering I am NOT a runner though, and did not train for the event, I was proud of finishing in less than half an hour (my goal). I am sure I could not have done this if I was not in relatively decent shape. I seriously doubt the race helped me get in better shape.

    Unfortunately, the experience has me wanting to participate in another one. Here’s the question: How un-primal is running a 5K or 10K?

  23. I much prefer shorter blurbs. Often I wish to read your articles Mark, but they take too much time!

  24. Keep em long. I come to your blog for information. I thirst for it. You’re a heckuva writer with a lot of knowledge, and I have benefited from your experience and insight.

    Dance with the one who brung you. Just look at the success of your site and how many hits it gets.

  25. I’m one of the folks who are glad they did a half marathon. I walked it. Did not finish last.

    I trained according to Primal fitness, despite never having heard of Primal.

    It does give you a sense of accomplishment. Wouldn’t recommend it for any other reason.

  26. Haha I love how “Grilled Beef Heart with Roasted Chili Peppers” is a related post.

    It’s disturbing to think how many other “facts” touted by Conventional Wisdom are completely false.

  27. how DO you have this timing, Mark??? i am toying with a sprint or olympic distance tri–it would be my first but I’ve raced a mile in swim comps and I swim and mtn bike a lot. I’d be well trained. i know excessive cardio isn’t great but i want to do a tri just once and i do like training…maybe train with lots of tabata/intervals and not too many super long workouts.

  28. So, the point of this monday musing (unless I’m mistaken), is:
    Train properly!
    Don’t run a marathon if you’re not physically fit to do so!

    excuse me, but well, DUH!

    I’m pretty sure that whoever needs this advice probably isn’t wise enough to search for it here.

  29. I had a cousin who was a vegetarian all his life due to the strange SDA church. He marathoned all the time, thinking he was in superb shape. Until his heart chamber broke, and blood rushed into the wrong territory. He almost died, 70 percent heart damage. He told me afterward, the vegetarian diet, let alone the long distance running didn’t do a damn thing for him but hurt him.
    I think by looking at a marathon runner compared to a 100 meter sprinter, the muscle physique tells it all. Long distance runners are basically “skinny fat”.

  30. There is a big difference between running one marathon (or a half) a year and 10 a year. Big differnce between running 10 miles in a week and 60 miles in a week.

    If you enjoy being active and you want to run a half marathon, have at it. You’re not going to run it in 90 minutes…which is were the danger would lie if you were not trained for it. If you run it in 2 hours…your basically jogging and I don’t think any relatively “fit” person would even breathe heavy during it.
    I like to run 5k and 10 k races (and an occasional half marathon)…I don’t run on a regular schedule, but it’s fun to go out on a Sunday morning and enter a race. You’re not going to win it…so enjoy a nice 3 mile run (or more) with lots of upbeat people around you. Just don’t eat the bagels offered after the race 😉

    I think running is just fine if you enjoy it….some of the hunter gatherer tribe members were persistence hunters, other were not…I don’t think there is any benefit to train to be able to run a marathon in 3 hours.

    Just my 2cents.


  31. Getting back to the topic of the study – the results showed that the runners that had damage showed no damage after three months. That’s not to say that it took three months for them to heal. They checked the runners 6-8 weeks before, right after, and then 3 months after the marathon. Since the researchers had no definitive evidence to suggest a shorter time to heal (due to not checking until three months later), they say “up to three months.” Regarding the PB, I’ve run 1 marathon and 7 halves (all after ACL reconstruction) and have to say that doing speedwork (like sprints or slightly longer intervals – up to half-mile repeats) are what make me faster when it comes to running the 13.1mi, but of course, one has to slowly build the body up to running that distance through long, slow runs or risk injury. I’m going to keep running, but I’m fairly new to the PB, and am going to give it a shot, because as they say, I’d rather look fit than be fit.

  32. Dear Mark,

    With the amount of great reasearch you’ve read zou can’t possibly have missed Born to Run by Christopher McDougall. There he talks about runners who run frickin ultras of a 100 miles or more! Oh and they never get hurt!

    How would you explain such extraordinary performances? Is it because the athletes are burning fat instead of carbs and can therefore keep it up for so long?



    1. There is a huge difference between elite road marathoners and elite trail marathoners.Road marathoners these days are practically sprinting for just over 2 hours,bordering on an anaerobic effort.That is impossible on any decent trail.
      There is also a big difference in body build,trail runners are more muscled due to going more slowly and constantly adjusting for varied terrain.

      1. The presenter of the theory called it a “leading theory”, but only in his own mind. The theory is just that, as a previous distance runner converted now to the primal exercise mode, I can vouch many fitness and health gains. I have direct proof that my heart arrhythmia has now healed as a result of ditching long distance running.

  33. Hmm I have mixed feelings on the subject. I think it’s great if you make sure you’re running at your own level and not setting out to break a record. I think that kind of thing just kind of has to happen on its own.

  34. The only reason I never really got into jogging (I did it a few times, it was OK) or marathon running (I considered running the London Marathon) is because it’s DAMN BORING.

    Plus all the people I see jogging around my area are skinny-fat or flabby all year round…

  35. I signed up for a marathon a couple of months before finding MDA, just before going Primal. I realized the risks while reading Marks blog here, and completed the marathon a few weeks ago.

    I felt super and had a great run! But, it was not easy on the Primal Diet… in fact, I had to throw some carbs and glucose gels back in within the last month before the marathon to make it work (I tried training primal without the carbs and it was not fun, I bonked severely every time after about 14 miles).

    There are certainly physical risks taken in completing a marathon, and resulting damage. There are also physical risks involved with lifting heavy things and sprinting, and resulting damage. The difference is that the marathon increases the time that it takes to recover physically by quite a margin.

    I think what needs to be mentioned beyond possible heart damage or physical damage, is that training for and running a marathon causes a much worse short term problem. It causes the body to become ultra efficient at that particular effort… Over time, with distance training, you lose fast twitch muscle mass and start burning less calories over the course of the long run. This in itself is part of our bodies incredible ability to adapt to physical demand. But, it does not help Grok burn more calories or excess fat off the body, or retain any decent muscle mass. So I will say this… if anyone reading this is on the PBD, and is seriously considering running a marathon, or has already signed up for one, I would tell you that you have some serious challenges ahead and if you really want to complete a marathon you will need to sign off this amazing diet at least a month before the marathon.

  36. hey I just had a thought: maybe the marathon will “take out” Subway Jason. That’ll show ’em…

  37. Short posts, long posts, doesn’t matter: I’ll read ’em.

    Here’s an idea for a musing: alcopops, aka, blackout in a can. Anyone who has a teenager (or is a teenager) should be very, very scared of their popularity.

  38. The only marathon I plan to do is thru-hike the Pacific Crest Trail next year, and that will take 5 months (Mexico – Canada).

  39. I don’t disagree that there are physical risks but I also think the motivational benefits for beginners outweight those risks.

    Motivation is why people fail to become healthy. If training for a marathon motivates them then by all means. Is it risky? Sure, but less risky than sitting in front of the TV eating twinkies.

  40. Definitely in favor of seeing some shorter, musing-style posts. Food for thought is great, even in bite-sized form.

    On the whole marathon thing… personally, I took up martial arts so that I wouldn’t have to run, but I have been flirting with some HIIT-style sprint workouts lately. My SO is big on endurance sport, though, and insists that cross-training will fend off any ill effects–of course, she’s also prone to migraines, hypoglycemic events, various illnesses, and already has arthritus in her early 20’s, whereas I’ve had one flu bug in the last two years and that’s it. So go figure.

  41. Gal, I couldn’t agree with you more about motivation. It all comes down to preferences; some people get excited about the idea of a big challenge, others want to curl up and die at the thought of endless hours training for a long road race.

    I think it’s far more important that you’re doing something you enjoy for the right reasons. Poor training may well give lasting damage but it doesn’t follow then that marathons = unhealthy. Look at Stefaan Engels (guy who’s running a marathon every day this year) for eg – a shining example of fitness.
    (Shameless use of a sample of one to prove a point I know…! )

  42. “Total beginners with a new pair of $150 Nikes (with shock absorbers, stabilizers and motion control) and a fanny pack full of glucose gel can sign up for a marathon and (just) do it. ”

    Interesting point. I don’t think I could “just do a marathon”. I did so (well I trained though not enough) with a half marathon (it included lots of walking), and paid with walking down the stairs backwards for three days. Ouch.

    Anyway, the marathon is still a goal and same goes for the Ironman. Bite me.

    1. Ironman is still a goal for me too! Failed last year due to poor training, gonna get it next year (2013) though!

  43. Definitely down with the Monday Musings idea Mark!! I dig it. This is one thing I liked about the recent NYC Barefoot run. They didn’t set a distance so that everyone ran what they felt capable of. Something I could see catching on in favor of marathons over the next decade.

  44. Yes, more short posts please!

    Though the more posts, the harder it is to find something on the site 🙂 Thinking of it, I think the site’s search function is already not sufficient anymore to find something. It would be great if there was a search function that could be limited to title only. Currently even the comments seem to be part of the search, resulting in usually dozens of articles for any given search.

  45. There been increasing evidence that overtraining in endurance is very harmful to your body. Heart disease and early hair loss are just 2 of the side effects.

  46. Geoff,

    That exactly what I am doing! Good results with Dr. Maffetone, heavy lifting, sprints, and good diet.


  47. Wow, really interesting post and discussion. For my part, I’ve run 60 full marathons (in the last 2.5 years), so I FREQUENTLY get told that I’m probably doing my body damage. However, I’ve been lucky enough not to have any serious injuries thus far, and I think it’s in large part due to the relaxed approach I take to long distance running. I believe it’s healthier to run MORE marathons more frequently – it takes away the pressure to do well in one particular race regardless of how you’re doing that particular day (i.e. friends who run one marathon a year will a push for a PR no matter how they’re feeling; I wait until the midpoint of every race before deciding if I want to race it or just relax and finish while having fun). Plus, by doing more marathons, your body adapts to the distance much better than a typical training plan of doing one 22 mile run and the rest all much shorter. My favorite part of a marathon is always miles 20-26 – I typically maintain the same pace because it’s still comfortable for me, while others are slowing down because it’s uncharted territory and their bodies can’t take it.

    I suppose it remains to be seen whether or not I’ll have heart problems, as I’m only 25 right now… but hey, I don’t take any drugs, so maybe I can be one of those in that study DC wants 🙂

    1. Its the unseen damage that is worse, accelerated ageing, heart problems, etc, these won’t hit you until a few years of doing this.

      The candle that burns twice as bright burns for half as long…

  48. Since 03 I have done about 80 triathlons.I have been living primal for 6 months and I have never felt better.The hardest thing for me was telling my type A traning partners I am going for a 2 hr hike instead of a 4 hr sufferfest on the bike.Still I have some isssues.I have a hard time letting people pass me on the bike path to work.

  49. What about running marathons because you love to run marathons? I don’t knock myself out, but I barely get warmed up by 5K. Do you really think Grok ran down his prey in ten minutes? Persistence hunting is all about running for hours to wear out that beast.

    1. Grok devised weapons and traps and worked in small groups to hunt their prey. Grok used incredible sprinting power to move in for the kill. Grok would not have had the energy and caloric intake to run long distances eating animals, nuts, berries, and root vegetables. If Grok had access to GU or huge bowls of pasta that could have been done, but then again, Grok would not have needed to persistently hunt an animal with huge bowls of pasta readily available.

  50. I completely agree with this. We have some overly competitive athletes that do not understand that too much is a bad thing. Every time I turn around they are running this marathon or 1/2 marathon or mud run in addition to their normal training…And Mark is spot on, THEY ARE A STUBBORN BUNCH.

    1. Yes, have seen this first hand, even as their health fails, and they loose lean body mass, and actually gain fat. Since I ditched the running and focused on resistance training, my body fat has hit an all time low (7%) – when running, I was at 20% and it stubbornly refused to drop, even worse, it was stored around the waist. I see many marathon runners with great V02, but they are actually flabby – thin, flabby, weak, sickly things…