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Archive for August, 2009

Running marathons makes your memory worse…and better

August 2nd, 2009

This is a neat paper on how running affects the mind, with a surprise twist. (Check out Frontal Cortex and Neurocritic for more detailed discussions.) Researchers at Columbia University wondered whether the extreme stress of running a marathon might trigger hormones in the brain that would temporarily alter how our minds work. It’s a reasonable assumption:

Indeed, [the researchers write] cortisol levels recorded 30 min after completion of a marathon rival those reported in military training and interrogation (Taylor et al., 2007), rape victims being treated acutely (Resnick, Yehuda, Pitman, & Foy, 1995), severe burn injury patients (Norbury, Herndon, Branski, Chinkes, & Jeschke, 2008), and first-time parachute jumpers (Aloe et al., 1994).

So does running disrupt your memory? Yes. The researchers tested Boston and New York marathon participants, either a few days before their race or within 30 minutes of finishing, and the post-race tests showed worse performance on a set of verbal memory tests. That’s an example of “explicit memory,” where you consciously remember events and facts. But here’s the surprise: the researchers also found that the post-race testees did better on tests of “implicit memory,” which is how you store information that you don’t need to access consciously, like how to ride a bike.

In other words, it appears that being under stress (and marathons definitely count as stress!) causes you to tap into the older, reptilian part of your brain, where instinct and intuition dominate.

[Thanks to Kyle for the tip. I’m heading out the door in a few hours for a week-long canoe trip, so expect the next blog update around August 10. Happy long weekend!]

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Running to prevent glaucoma, cataracts and macular degeneration

August 1st, 2009

For the last 18 years, Paul Williams of Lawrence Berkeley Laboratory has been following 55,000 runners as part of the the National Runners’ Health Study, which has incredible statistical power thanks to its size and duration. These days, Williams churns out new studies like clockwork, showing the association of running with various health risks and body parts. Most recently, it’s the eyes: in three separate studies (one in Medicine & Science in Sports & Exercise, two inĀ  Investigative Ophthalmology and Visual Science), Williams shows that running reduces the risk of glaucoma, cataracts and macular degeneration. The mechanism isn’t entirely clear (epidemiological studies like this shows correlations, not causes), but Williams speculates that aerobic exercise may reduce “intraocular pressure,” the fluid pressure behind the eye.

What Williams really emphasizes in his recent studies is the “dose-response” relationship between running and health: the farther and faster you run, the greater the benefits. In this case, for instance, every additional kilometre in your average daily run lowers your glaucoma risk by five percent. Also, the faster your best 10K time, the lower your risk — in fact, there were no reported cases of glaucoma for runners who could run 10K faster than 33:20! This is quite different from the usual government health recommendations that advocate a fairly minimal amount of moderate exercise each week, and make it sound like there’s no particular benefit in doing more.