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April 9, 2010

LSAT Logic and Running Shoes

LSAT Blog Logic Running ShoesIn Born to Run, Christopher McDougall claims normal athletic shoes are actually bad for your feet. He suggests it's best to get as close to running barefoot (NYMag) as possible.

Being an LSAT dude, I'm pretty skeptical of things I read at first, especially when an author makes big claims.

In a nutshell, McDougall says many foot problems and foot/leg injuries today are a direct result of our footwear. He thinks cushioning and support are bad. They negatively impact the way we run and walk (heel down first = bad), and they make our feet and leg muscles weak so that we can't handle the impact of running this way.

He offers a lot of support for this, but let's look at one particular piece of evidence in isolation.
Runners wearing top-of-the-line shoes are 123 percent more likely to get injured than runners in cheap shoes, according to a study led by Bernard Marti, M.D., a preventative-medicine specialist at Switzerland’s University of Bern.
Reminds you of an LSAT Logical Reasoning stimulus, doesn't it? I'll add McDougall's conclusion (in my words): "Therefore, design flaws in top-of-the-line shoes are the cause of these runners' injuries, and they'd be less likely to experience injuries if they switched to cheap no-frills shoes."

Let's think about the evidence and conclusion here and examine for potential flaws.

The evidence regards a correlation (in this case, a direct relationship) between top-of-the-line shoes and a greater number of injuries. Similarly, there's a correlation between cheap shoes and having fewer injuries (than those with top-of-the-line shoes).

Can we conclude from this that the top-of-the-line shoes are actually causing the injuries? It's possible, of course, but there are other potential explanations.

The LSAT's Logical Reasoning section frequently contains arguments where the author confuses correlation with causation (and whenever studies or surveys are presented, there's usually some sort of flaw in their construction or interpretation).

For this reason, I immediately started thinking of alternative explanations:

-Maybe injury-prone and inexperienced runners are more likely to buy fancy and expensive running shoes (hoping the shoes will be a substitute for good technique and actual exercise!)).

-Maybe people who have fancy and expensive running shoes take more risks while running (and thus, it wouldn't actually be the design of the shoes that is at fault - it'd be the runner's fault).

-Maybe people who have fancy and expensive running shoes spend more time running and are thus at greater risk of injury (like the previous alternative explanation, the runner's behavior is to blame for the injuries, not the shoes).


McDougall provides additional evidence
If that one piece of evidence (the correlation) was all McDougall provided to support his argument, I wouldn't take him seriously, given the alternative possibilities.

He's smarter than that, though, and provides dozens of pieces of evidence to support his argument about modern shoes. He also gives additional support for the particular study described above:
Dr. Marti’s research team analyzed 4,358 runners in the Bern Grand-Prix, a 9.6- mile road race. All the runners filled out an extensive questionnaire that detailed their training habits and footwear for the previous year; as it turned out, 45 percent had been hurt during that time.

But what surprised Dr. Marti, as he pointed out in The American Journal of Sports Medicine in 1989, was the fact that the most common variable among the casualties wasn’t training surface, running speed, weekly mileage, or “competitive training motivation.” It wasn’t even body weight, or a history of previous injury: it was the price of the shoe. Runners in shoes that cost more than $95 were more than twice as likely to get hurt as runners in shoes that cost less than $40.
(Source: Born to Run, p171-2)

McDougall tells us that Dr. Marti was considering potential alternative causes such as "training surface, running speed, weekly mileage," and "'competitive training motivation.'" Of course, perhaps there's something else Dr. Marti failed to consider, but he seems to have considered, and dismissed, some of the biggies. In short, Dr. Marti's argument appears to be pretty good so far.

However, there are still other areas to attack in this study now that we have more information.

Is 4,358 runners a large-enough sample size? We might want to think about how big the running community is in general.

Is the previous year enough of a period to look at? Perhaps we want to go back further in time.

What sort of runners go to the Bern Grand-Prix race? What sort of runners run a 9.6-mile road race? Maybe racers in general aren't representative of the running population.

You won't always have to go this far into your analysis of a particular argument, but it's good to be skeptical. Always think about alternatives. Think "what if?"

***

As for me, I'm enjoying running barefoot. Let me know if you want to go for a run in Central Park sometime!

Photo by mikebaird / CC BY 2.0



4 comments:

  1. Yes I love to run with you in Central Park! Lol

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  2. I just got a pair of FFs last month, too. I read McDougall's book, but I wasn't fully convinced until reading the article in Nature recently from David Liebermann's lab at Harvard. He showed that although the overall forces on the body and the joints are the same, the rate that the forces are applied (AKA the "jerk") is much less for people who run on their forefoot. Not to mention that they feel really cool. I've loved them so far. Too bad I live in Oregon, or I'd come run with you.

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  3. I don't really know where to post this but as I was going through Flaw In Reasoning questions on the Next 10 LSATs I came across a question (PT 37, S4, #17) that, if I'm not mistaken, had two legitimate flaws in the reasoning and both were listed in the question stem. I chose the cause and effect flaw (that the author assumes a causal relationship instead of a correlation), yet the correct answer listed was a numbers flaw. Now I realize that you are supposed to choose the BEST answer, but whose to say one type of flaw is better than another? Thank you so much for all your amazing help!

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  4. Okay, this is why I sucked on my first LSAT. I know I can't argue with the LSAT, but I can't turn it off. I'm questioning the question. And here is how I questioned the notion that this was bad reasoning.

    This is what I heard from your summary of the argument:
    Extra cushioning and support that focuses on comfort (that are more often found in more expensive running shoes) creates conditions which cause us to adapt our running styles/form (heel down first, etc.) which THEN makes feet and leg muscles weak.

    Okay, so science shows that bad technique produces week feet and leg muscles and that bad technique (along with the now weakened leg and feet muscles) leads to injuries.

    So the author's argument is not that expensive shoes are bad for you but that the cushioning (and other stuff...maybe focus on comfort rather than proper running technique...or maybe cushioning period hampers the technique of running barefoot) in the expensive shoes is bad for you.

    So I would be okay with the logic expressed as "expensive shoes are bad for you and cheaper shoes are better for you" because there is a scientific correlation between bad technique and injuries. Apparently, the false assumption I am making though is between expensive shoes and proper technique. But still, the point of the argument is that expensive shoes have an unhelpful goal (making the consumer comfortable) which does indeed create an environment where this sort of correlation could be made appropriately.

    I hear you wanting to go back to sample size (representativeness, etc.) of ways to show the argument false. But to me that sounds like it misses the scientific evidence that there is a correlation between technique and injuries.

    DO YOU SEE THE MENTAL MESS I AM!! HELP!

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