February 26, 2015

Run Slowly, Live Longer? Exercise Thresholds May Be Key

rackham drawing via wikipedia

Guest Post by Tiffany Reiss

I'm pleased to present another thoughtful post by Cranky Fitness contributor Tiffany Reiss, who as you may recall is a university professor and actually knows something about exercise physiology! She's also one of the innovators behind the website The Hub Edu, which enables users to build a digital library of resources and share with others.  (In beta but very cool, and free!) More about Tiffany can be found by scrolling down on our info page.  --Crabby

The Tortoise and the Hare

As I child I grew up watching all of the Disney movies. My mother loved them and in turn, we watched them. We also watched “Wonderful World of Disney” on Sunday evenings and I remember seeing this Tortoise and Hare Disney short film numerous times on those special Sundays:

The moral of the story is clear. Slow and steady wins the race. But really, the hare seems so much more exciting and seems to have a lot more fun. Maybe I was just delusional but I would still have preferred to be the hare as opposed to the tortoise. Our society seems to agree and support this infrastructure and “speedy” mentality.

However, if some of the latest research is correct, it looks as though that tortoise might have had it right all along, especially when it comes to running.

Several new studies have suggested that we really can get too much of a good thing. There is a new idea of what might be referred to as an "exercise threshold" for each individual. Once we reach ours, exercising more might not impart any benefits and in fact, might actually have a negative impact on our overall health.

These studies particularly focus in on dose- response to exercise and if this preliminary research holds true, slow and steady might really win the mortality race, but only when considering running. Here is what a synopsis of all of this latest research and what it suggests:

1) Yes, you do have to exercise. People who exercise regularly have a lower overall mortality rate than their sedentary counterparts.

2) Yes, those who do push themselves a little harder (or more intensely) also have a lower overall mortality rate than those that never push themselves at all, even if they are still “exercising” for long durations. This seems to hold true for walking intensity and cycling intensity in particular.

3) As you may have seen in recent headlines about exercise intensity and mortality, when running or jogging, no, you don’t have to run a 6 min mile to see positive health benefits. In fact, a recent study out of Copenhagen suggests jogging at a slower pace might actually be better for us than running at a faster pace more often. (For additional media coverage, Time and the New York Times also weighed in).

So what does all of this mean? First it’s important to note that although this research is compelling, it’s just a few pieces of the overall puzzle. These studies are looking at dose-response to various modalities of activity and overall mortality rates. Lots of things can kill us and it’s not just chronic diseases (though statistically, if you aren’t killed in an accident or die from an acute illness, you will likely die of some kind of chronic disease or complication from one). Again, statistically, if you move and the more you move, you lower the probability of developing a chronic disease. It’s never a 0% probability however, no matter how much you exercise.

Second, why does it seem to differ between walking, running and cycling?

Well let’s think about this physiologically and biomechanically. Running and walking are “harder” on the body than cycling because they are what we refer to as “relative to body weight” activities. Running is a lot harder on the body overall than walking physiologically speaking because of biomechanics. When walking, every time you take a step you have force coming up from the ground (ground reaction forces) and force bearing down from above (gravity) playing a role in the forces acting on the body. Friction between the foot (or shoe) and surface also play roles here but not enough to discuss right now. When running, those forces multiply by a large factor so more overall force is absorbed by the body when running and it has to go somewhere (Sol, 2001). That force is distributed through the body and therefore running causes a lot more damage to the body than just walking. And of course, body weight and body size will play a role in this as well. With cycling there is even less damage because you don’t have to deal with those ground reaction forces.

Now that explains the modality discrepancies but what about that intensity factor? Again, let’s think about this physiologically speaking. Even jogging is more intense than just walking as far as energy expenditure (and damage to the body) and running at a faster pace even more so (because you can go much further in a shorter amount of time). Intense exercise can be very good for us, but not all the time. Adequate rest days are necessary when exercising at such a high intensity. Higher intensity = more damage to the body = more rest or lower intensity activities in between. For those individuals who exercise at very high intensities (including running very fast for long distances) they need to balance this with adequate rest and recovery. Again, we are taking about elite and highly fit athletes and individuals here. For most of us, this isn’t the problem. For the rest of us, ramping it up a day or two might actually be more beneficial to us.

As this research continues, we may eventually truly better understand this idea of an exercise threshold and my guess is it will be different for every single individual based on genetics, age, size, shape, etc.... In the meantime, for the majority of us, it is still better to just keep moving…more frequently, and from time to time, more rapidly.


  1. All I want is to cut a bargain with my body. I will work out 1 hour, 2 hours even 3 hours as long as we go at my 70% effort level. I know this short bursts of high intensity is supposed to be really good for you but It is just too stressful and exhausting. Which is probably my sign that I need to work on it. Pretty much all cardio I do is low impact so that is part of the problem.

    1. I think the most important thing is moving....70% is still pretty intense!

  2. Tiffany,
    Very interesting, and it's good to hear from an expert as opposed to rumors. :-)

    It will be interesting to see how this research proceeds. It also illustrates how maddeningly complex exercise factors are.

    For example, I prefer not to run much, fast or slow. I don't want to spend that much time, and I don't want the repetitive strain injuries that will ensue with too much distance running. But for some people, nothing but running/jogging will do. When I do run, I sprint short distances, and infrequently, so I recover.

    As alluded to above, too much intensity leads to breakdown. And even too much very low intensity work can probably induce overtraining. :)

    And then there's the college factor: when testing theories in a university setting, one needs subjects. The easiest subjects to find are, guess what, untrained college students, so results are skewed accordingly that. :) If somebody really is thorough with their methodology, they do their best to overcome that, and it sounds like the studies above may have been diverse enough to make that happen.

    Just as you say, amongst the reams of data and opinions, just keeping moving, and not overdoing it, is probably a good approach. :)

    1. Your just keep moving for some reason reminded me of Finding Nemo:
      For some reason Disney seems to be on my brain!

  3. Great post, Tiffany. Figuring out what to do - how much, how hard - it is all so confusing! And in my case, I have found exercise fairly addictive & seem to want to add hours and hours. Having said that, I have a friend with atrial fibrillation which seems to have at least some degree of a tie to long-term endurance sports (he ran the Western States 100 several times, then got into serious bike racing), which is worrisome. I often wonder if the real answer is that there is not a single answer that will suit everyone equally - but of course that would be even harder to find and prove in studies.

    Well, at least the subject is (to me, anyway) endlessly intriguing. As my name here shows, I am still leaning towards overdoing a bit, but maybe this sort of study will eventually bring me to my senses. Thanks for the update!

    1. Exercise can be very addictive, especially running for some reason. That's another blog post however. You might find this article from the NYT interesting. It includes the link to the original article regarding scarred heart tissue found in many older long distance runners.


  4. I've been a runner for a long time and have just in the past couple of years realized that my body tolerates it much better now when I don't run at max exertion very often. Sadly, it has taken years and many injuries to get to this point. Hopefully by cutting back on the intensity I can keep logging lots of miles for years and years!

    1. I think too, it's about finding that balance which does shift as we age. Cross-training also seems to help, especially runners if you are interested.

  5. It sounds like moving daily, and moving fast a bit of the time, is about the best bet.

    1. Statistically speaking, yes. It is just about moving daily and variety in what we do and how we do it (modality, duration, frequency, intensity).

  6. this tortoise is slowly getting happy about this news :-)

  7. I've always thought "no pain, no gain" was the most nonsensical advice ever. I'm not fond of pushing myself hard, even in intervals. I don't run, because it hurts, and has ever since I was a preschooler. The people who can run without pain a lot of the time are welcome to it. I can walk a lot without pain, so I do.

    Mary Anne in Kentucky

    1. My favorite t-shirt says "No Pain, No Pain" and I only wear it once in a while so I can have it forever! It was given out at a bike ride a few years ago - a ride that was more or less a series of jokes about Tour de France. The routes included a 10 miler, a 20, and a 35, and a once-around-the-block followed by brunch with a county supervisor. As the announcer said, they had no idea how we'd gotten to the finish line, and we got the t-shirt regardless of route chosen. Although I happen to like to run - a little, and ride - a lot, this non-competitive attitude made it my kind of event.


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