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:
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.