Can exercise make the brain more fit? That absorbing question inspired a new study at the University of South Carolina during which scientists assembled mice and assigned half to run for an hour a day on little treadmills, while the rest lounged in their cages without exercising. ...

At the end of the two months, the researchers had both groups complete a run to exhaustion on the treadmill. Not surprisingly, the running mice displayed much greater endurance than the loungers. They lasted on the treadmills for an average of 126 minutes, versus 74 minutes for the unexercised animals.

More interesting, though, was what was happening inside their brain cells. When the scientists examined tissue samples from different portions of the exercised animals’ brains, they found markers of upwelling mitochondrial development in all of the tissues. 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.

[While there's no doubt that exercise is good for the body, wouldn't the brain be made fitter by thinking rather than running?]