考研阅读精选：体育锻炼也可强健大脑
『最新研究显示，加强体育锻炼不仅可以使肌肉发达有力，也可强健大脑。』How Exercise Can Strengthen the Brain
体育锻炼也可强健大脑
Sept. 28, 2011 |From The New York Times
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Can exercise make the brain more fit? That absorbing question inspired anew study at the University of South Carolina during which scientistsassembled mice and assigned half to run for an hour a day on littletreadmills, while the rest lounged in their cages without exercising.
Earlier studies have shown that exercise sparks neurogenesis, or thecreation of entirely new brain cells. But the South Carolina scientistswere not looking for new cells. They were looking inside existing onesto see if exercise was whipping those cells into shape, similar to theway that exercise strengthens muscle.
For centuries, peoplehave known that exercise remodels muscles, rendering them more durableand fatigue-resistant. In part, that process involves an increase in thenumber of muscle mitochondria, the tiny organelles that float around acell’s nucleus and act as biological powerhouses, helping to create theenergy that fuels almost all cellular activity. The greater themitochondrial density in a cell, the greater its vitality.
Past experiments have shown persuasively that exercise spurs the birthof new mitochondria in muscle cells and improves the vigor of theexisting organelles. This upsurge in mitochondria, in turn, has beenlinked not only to improvements in exercise endurance but to increasedlongevity in animals and reduced risk for obesity, diabetes and heartdisease in people. It is a very potent cellular reaction.
Brain cells are also fueled by mitochondria. But until now, no one hasknown if a similar response to exercise occurs in the brain.
Like muscles, many parts of the brain get a robust physiological workoutduring exercise. “The brain has to work hard to keep the musclesmoving” and all of the bodily systems in sync, says J. Mark Davis, aprofessor of exercise science and senior author of the new mouse study,which was published last month in The Journal of Applied Physiology.Scans have shown that metabolic activity in many parts of the brainsurges during workouts, but it was unknown whether those active braincells were actually adapting and changing.
To see, the South Carolina scientists exercised their mice for eight weeks.
At the end of the two months, the researchers had both groups complete arun to exhaustion on the treadmill. Not surprisingly, the running micedisplayed much greater endurance than the loungers. They lasted on thetreadmills for an average of 126 minutes, versus 74 minutes for theunexercised animals.
More interesting, though, was what washappening inside their brain cells. When the scientists examined tissuesamples from different portions of the exercised animals’ brains, theyfound markers of upwelling mitochondrial development in all of thetissues. Some parts of their brains showed more activity than others,but in each of the samples, the brain cells held newborn mitochondria.
There was no comparable activity in brain cells from the sedentary mice.
This is the first report to show that, in mice at least, two months ofexercise training “is sufficient stimulus to increase mitochondrialbiogenesis,” Dr. Davis and his co-authors write in the study.
The finding is an important “piece in the puzzle implying that exercisecan lead to mitochondrial biogenesis in tissues other than muscle,” saysDr. Mark Tarnopolsky, a professor of medicine at McMaster Children’sHospital.
The mitochondrial proliferation in the animals’brains has implications that are wide-ranging and heartening. “There isevidence” from other studies “that mitochondrial deficits in the brainmay play a role in the development of neurodegenerative diseases,” Dr.Davis says. Having a larger reservoir of mitochondria in your braincells could provide some buffer against those conditions, he says.
More immediately, Dr. Davis speculates, re-energized brain cells couldbehave like mitochondrial-drenched muscle cells, becoming more resistantto fatigue and, since bodily fatigue is partly mediated by signals fromthe brain, allowing you to withstand more exercise. In effect,exercising the body may train the brain to allow you to exercise more,amplifying the benefits.
Revitalized brain cells also, atleast potentially, could reduce mental fatigue and sharpen your thinking“even when you’re not exercising,” Dr. Davis says.
Of course,“mouse brains are not human brains,” Dr. Davis says. “But,” hecontinues, “since mitochondrial biogenesis has been shown to occur inhuman muscles, just as it does in animal muscles, it is a reasonablesupposition that it occurs in human brains.”（720 words）
文章地址：
http://well.blogs.nytimes.com/2011/09/28/how-exercise-can-strengthen-the-brain/
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