Some thoughts on current recommendations regarding exercise volume and intensity:
This has been bugging me lately. The current recommendations regarding physical activity go something like this: moderate activity (walking etc.) for thirty minutes four to five times a week is sufficient to reap most of the benefits of physical exercise.
Sounds too good to be true and that alone is a reason to look into it some more.
The recommendations typically come from professional medical associations and, while there is nothing wrong with that in itself, it is something to be kept in mind, because of the focus on damage control and management of public health issues is what drives these organizations.
Practically that means that any official recommendation must avoid discouragement of the target population and that population is most easily discouraged by recommending more exercise than they can imagine doing. Hence the quest for finding the lowest dose of exercise still conferring a substantial benefit. Again, there is nothing wrong with that in itself.
The recommendations must be evidence based as much as feasible and the body of research supporting the recommendations is indeed substantial.
Most of the research is observational/epidemiological with some experimental science as well.
The problem is the following: study after study shows that subjects with very modest volume and intensity of exercise have very substantial reductions in mortality when compared with inactive people and that the cumulative benefits of higher levels of physical activity are less impressive.
So far so good, but when one looks at the actual level of exercise performed by the moderately active subjects, one cannot fail to be impressed by how little physical activity that actually is. For me personally, 100 to 150 minutes of walking per week doesn't even count as exercise but is just my normal activity level.
If this moderate activity group is so unimpressive and yet the difference in mortality is so striking when compared with the inactive group, a closer look at the inactive group is warranted. And sure enough, that group is rather extreme. In order to move around for less than 100 minutes a week one has to basically sit down on the couch and stay there for good.
All of a sudden, the impressive effects of moderate exercise are not that impressive anymore because one would expect that regular mobilization of someone slowly dying from being immobilized on the couch has major health benefits. This does not diminish the value of the research but it puts it in perspective: mobilization of patients with severe behavioral abnormalities resulting in voluntary immobilization has major health benefits and these can be achieved with 100 to 150 minutes of physical therapy per week.
Once the patient is mobilized and is getting off the couch here and there, the cumulative health benefits of more exercise diminish. However, this is again an expected result as we are not dealing with a patient slowly dying on a couch anymore, but with a normal person and the effects of exercise.
The question is how to interpret the research and apply it to one's own situation.
For the ultimate couch potato, it is easy: bring your activity level up to that of a normal person and you will reap major benefits. However, the message for a normal person who went through the trouble of figuring out their activity level and found that they are already getting their 100 to 150 minutes of activity, is not that they are already getting most of the benefits of exercise and do not have to do any more. In fact, they haven't gotten any benefit yet because they didn't start out as a patient. And yet, I have heard it over and over that a little itty bit of exercise is all what a normal person has to do to stay well.
Let me illustrate this fallacy with an analogy: imagine to be somewhat overweight at 230lbs and you are thinking about losing some weight. You do your research and you find convincing evidence that morbidly obese people weighing 350lbs derive major immediate health benefits from losing weight and that 90% of the benefit is realized with the first 100lbs lost. Would you conclude that you have already realized more than 90% of the benefit, give yourself a pat on the shoulder and decide to abandon your plan? Of course not. The research is interesting but doesn't apply to you directly because you are not morbidly obese.
Similarly, for a normal person, concluding that 100 to 150 minutes of moderate activity per week is sufficient amounts to nothing more than congratulating oneself for not being the ultimate couch potato. Perversely, the attempt to define the lowest effective dose of exercise in order not to discourage the taking up of exercise results in providing an excuse for not exercising in the normal population.
Bottom line: the lowest effective dose of physical activity to prevent death from extreme inactivity seems to be around 100 to 150 minutes of moderate activity per week. This factoid has no relevance for normal subjects evaluating the potential effects of exercise on their future health and well being. The dose response relationship between exercise and mortality applicable to the normal person begins at the lowest effective dose and benefits accrue at a much slower rate. Hence, a normal person must exercise at much higher volume and intensity to realize benefits than the official recommendations at first glance suggest.
The big question is, however, if the quest for finding the magic prescription for compensating for an unhealthy lifestyle with the smallest possible amount of exercise is a sane one at all. One of the more interesting recent research seems to show that sitting in itself is bad for ones health and the bad effects can only be partially compensated for by exercise.
Incorporating physical activity into daily life as much as possible and actually stopping to think about it as exercise may be the more attractive approach.
