Cigarettes may be useful for distance runners?!? (or, How to prove anything with a review article)

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Last winter the Canadian Medical Association Journal published a fascinating article by Ken Myers discussing the (as-yet unexamined) benefits of cigarette smoking on endurance running performance.  Ken is a friend and elite distance runner (we used to literally run with the same crowd while I was doing my undergrad in Calgary) so I was very excited and a bit confused when I saw his article.  Could smoking really be beneficial for distance runners like myself?

Here are Ken’s arguments:

  1. Serum hemoglobin is related to endurance running performance.  Smoking is known to enhance serum hemoglobin levels and (added bonus), alcohol may further enhance this beneficial adaptation.
  2. Lung volume also correlates with running performance, and training increases lung volume.  Guess what else increases lung volume? Smoking.
  3. Running is a weight-bearing sport, and therefore lighter distance runners are typically faster runners.  Smoking is associated with reduced body weight, especially in individuals with chronic obstructive pulmonary disease (these folks require so much energy just to breath that they often lose weight).

In the discussion, Ken goes on to point out that:

Cigarette smoking has been shown to increase serum hemoglobin, increase total lung capacity and stimulate weight loss, factors that all contribute to enhanced performance in endurance sports. Despite this scientific evidence, the prevalence of smoking in elite athletes is actually many times lower than in the general population. The reasons for this are unclear; however, there has been little to no effort made on the part of national governing bodies to encourage smoking among athletes.

Now at this point I assume that people are wondering how something this insane came to be published in a respected medical journal (as of 2010, CMAJ was ranked 9th of out 40 medical journals, with an impact factor of 9).  The answer, of course, is that the point of Ken’s article was to illustrate how you can fashion a review article to support almost any crazy theory if you’re willing to cherry-pick the right data.  Here is the paper’s abstract:

The review paper is a staple of medical literature and, when well executed by an expert in the field, can provide a summary of literature that generates useful recommendations and new conceptualizations of a topic. However, if research results are selectively chosen, a review has the potential to create a convincing argument for a faulty hypothesis. Improper correlation or extrapolation of data can result in dangerously flawed conclusions. The following paper seeks to illustrate this point, using existing research to argue the hypothesis that cigarette smoking enhances endurance performance and should be incorporated into high-level training programs.

While people might be able to spot the implausibility of smoking improving distance running performance, it’s a lot harder to spot with more specialized topics.  For example, if I were to argue that “Intervention X” influences body fat distribution and pulled together a few mechanistic resources supporting my arguments, it would be very difficult for an educated lay-person to know if my arguments were sound or not.  Which unfortunately is the situation almost all of us are in, anytime we read anything that is even slightly outside of our own area of research.

Even with systematic reviews, which are the highest form of scientific evidence, there is still a lot of room for subjectivity. You can develop a systematic review in a way that makes it more or less likely that you will find a certain outcome, just as you could with an individual study. Not only that, but the review depends on the objectivity of the people screening articles, who could (intentionally or accidentally) systematically include or exclude articles that may have an impact on the review’s ultimate conclusions.  And then of course the authors have to synthesize data and come to conclusions, both of which are mostly subjective activities.

That doesn’t mean that there is always a nefarious intent on the part of researchers – I would argue that there almost never is.  But take the phenomenon of “White Hat Bias“, where researchers distort “information in the service of what may be perceived to be righteous ends”. And even the most objective and ethical researcher is still going to be looking at data through their own world-view, which may cause them to miss something that is in the data, or to “see” something that isn’t really there.

The point being that whether you’re reading a blog post or a systematic review paper in a prestigious medical journal, you really do need to be skeptical at all times.


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ResearchBlogging.orgMyers, K. (2010). Cigarette smoking: an underused tool in high-performance endurance training Canadian Medical Association Journal, 182 (18) DOI: 10.1503/cmaj.100042

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31 Responses to Cigarettes may be useful for distance runners?!? (or, How to prove anything with a review article)

  1. JBarr says:

    Maybe Kitz is on to something?

    • Travis Saunders, MSc, CEP says:

      I knew there was a logical reason behind all of this. I bet the Brooks Project will require all their athletes to start smoking by the end of the year. It helped Herb Elliott!

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  4. MRR says:

    Very nice demonstration. Could you please link to the Open Access version of the paper whenever possible?
    (OK, Google Scholar is your friend, but still.)

    • Travis says:

      Glad you liked it! Sorry for the link in the reference – it’s generated by using the DOI, so it links to CMAJ by default. The links that I added to the post myself are to the open access version though. Annoying that CMAJ doesn’t link to that version as well.

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  9. Bob Allen says:

    This illustrates why having peer reviews on research is a good idea. An advantage of electronic publications is that peers and others can comment almost immediately to either confirm research and/or reviews and, when necessary, to point out inconsistencies and biases.

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  11. Edward Peters says:

    Perhaps the best conclusion is not ‘be skeptical at all times,’ since that seems to suggest we can reach for an objective perspective, the existence of which Saunders’s article blatantly argues against. Instead, perhaps we – as researchers and problem-solvers – should seek to remove our desires from our work. We often desire an outcome, as Saunders point out, that is not the most reasonable given the data we’re analyzing. But of course, we can’t reach an objective fly-on-the-wall perspective, so we must seek not to become super-human but to be reasonable, to support our own conclusions, and to demand of what we read that it does the same. In other words, maybe our best bet is not to ‘be skeptical,’ since that is too final, but to engage in conversation with the writers of what we read.

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  15. David Llewellyn says:

    Doesn’t this have relevance to the “circumcision prevents HIV, STDs, etc.” debate? Why is not this same sort of analysis applied consistently to all daring hypotheses? For that is what circumcision to prevent disease is. Never before in the history of medicine has universal surgery on a normal body part been suggested for the prevention of transmissible disease. Yet rather than look at the bias, cultural and religious, of the proponents and rather than look at the possibility of a false correlation, much of the international health community has “drunk the Kool-Aid” and is marching off the cliff with the circumcisers. Myers article is a warning to all who would adopt extreme measures without critical analysis.

    • Travis says:

      I don’t know much about that particular example, but I would say that it’s a good lesson to keep in mind when reading an article on just about any topic. Given that you bill yourself as “The Circumcision Lawyer”, one could legitimately question your bias on this issue as well, no?

      • RicardoD says:

        “I don’t know much about that particular example, but I would say that it’s a good lesson to keep in mind when reading an article on just about any topic.”

        This part of the response is legitimate, though it is essentially milquetoast, generic, and tends to brush off the significance of something that is done to a million baby boys in the US every year, without their consent and without any consideration as to whether they would be willing to accept all the risks of the surgery including loss of life or loss of entire penis, nor even whether they’d accept the significant alteration of their bodies, IF given a choice in the matter.

        “Given that you bill yourself as ‘The Circumcision Lawyer’, one could legitimately question your bias on this issue as well, no?”

        This part is sad; it is a classic ad hominem attack on Mr Llewellyn. It seeks to denigrate him and dismiss the validity of his question. It is widely used by advocates of circumcision, often as the strongest argument they have in any discussion. It implies, “What you say cannot be valid because you oppose circumcision.” What did Mr Llewellyn advocate that is brought into question by his position on circumcision, IF it IS opposition to it (or not)? He asked if the premise under discussion might not apply to the “science” in favor of circumcision; does it require lily white, unquestionably pure neutrality to pose such a question?

        Does your reflexive resort to ad hominem attack, when circumcision seems to you to be questioned, disclose a deeply held belief in, and support of, the practice of circumcision? One may be forgiven for wondering, no?

        • Travis Saunders, MSc, CEP says:

          Neuroskeptic explains the impetus for my “ad hominem attack” below.

          I’d just like to add that these comments are veering wildly away from the topic of this post. There have been other posts on PLoS blogs this week dealing specifically with HIV and circumcision (available here), and if you would like to have a useful dialog with people who are passionate about the issue then I would suggest you check it out.


  16. Neuroskeptic says:

    “This part is sad; it is a classic ad hominem attack on Mr Llewellyn. It seeks to denigrate him and dismiss the validity of his question.”

    Whoa whoa, hang on, that’s exactly what he himself did:

    “Yet rather than look at the bias, cultural and religious, of the proponents”

    You can’t have it both ways. Either you stick to the evidence and ignore the personalities or you don’t.

    Personally I suggest that you do. Always.

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