The Wild File

Your urgent inquiries about the world. Answered.

Jan 11, 2003
Outside Magazine

Q) When I dream that I'm exercising, does my body respond physiologically?
Mike Buckley, State College, Pennsylvania
IN A WORD, NOPE. Most of your muscles are in a quasi-paralyzed state during REM sleep, when vivid dreaming takes place. According to Jerome Siegel, a professor of psychiatry and behavioral sciences at UCLA's Center for Sleep Research, the human brain, probably as a result of evolution, turns off the motor neurons so we won't injure ourselves or our sleeping partners—and so predators won't be drawn by our movements. While some people suffer from REM behavior disorder, in which the muscles don't shut off properly and the subject moves around or sleepwalks, we have yet to hear of anyone sleep-running a 10K. Vital signs such as heart rate may be affected by dream content, so visions of Sugar Ray Robinson sparring with you probably have a different effect than visions of strolling down a beach; still, without any muscle contraction, the fitness factor would be nil. This leaves the rather subjective idea that an exercise dream can make you feel better. To date, no studies have addressed endorphin rushes in sleeping people. Our take: If you dream you've just claimed the yellow jersey from Lance, more power to you, but the chances that it's made you fitter are about as good as if you'd sat through Breaking Away for the ninth time.

Q) Why do flies need compound eyes?
Shirley Beck, Olympia, Washington
LIKE ALL INSECTS, flies have compound eyes made up of numerous facets, or ommatidia. Houseflies have about 350 facets per eye, while dragonflies have a whopping 30,000. According to John Meyer, an entomology professor at North Carolina State University, each ommatidium feeds the brain data about its own segment of the field of vision, producing an image like a pixel on your computer screen, and these form a mosaic in the fly's brain. This information—essentially describing light and color—is fairly limited compared with what the human eye takes in, so insects have poor long-distance vision. But their compound eyes provide two important advantages. First, they allow the fly to detect movement much faster than we can, because their flicker fusion rate—the speed at which the eyes can fuse separate images into a continuous "movie"—is five times greater than ours. This is why flies can elude capture and zoom at insane speeds without crashing. Second, since compound eyes are spherical, flies can see what's behind them. So no matter how stealthily you sneak up on the buggers, they see you coming every time.

Q) How do mountaineers decide where base camp goes?
Bill Lee, Troy, New York
THERE'S NO DECREE from on high regarding where base camp should be located, says Seattle-based climbing guide Eric Simonson. Nor is it stated that every mountain has to have one. But when it comes to the big peaks like those in the Himalayas, "BC" is usually established, he says, simply "at the end of the road," the point beyond which you have to stop relying on trucks, animals, and porters and start climbing. It needs to be low enough—generally below 15,000 feet—for climbers who are sick or tired to go there to recover, yet not so low that starting back up takes too long. If you're looking for an appropriate site, you'll want it to have sunshine, flat ground, and clean water nearby, plus protection from wind, avalanches, and rockfall. Not surprisingly, the BC on Everest's south side is considered one of the world's most forbidding. According to American climber Ed Viesturs, this legendary camp, on the moraine of the Khumbu Glacier at over 17,500 feet, is so high that recuperation is difficult. So what's the cushiest? At a mere 13,369 feet, the base camp on Pakistan's 26,660-foot Nanga Parbat is composed of a sunny, grassy moraine with a peaceful stream and oodles of wildflowers—what Viesturs fondly calls "supreme flip-flops-and-shorts territory."

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