The New York Times on how exercise raises the level of glycogen available to the brain:
After the single session on the treadmill, the animals were allowed to rest and feed, and then their brain glycogen levels were studied. The food, it appeared, had gone directly to their heads; their brain levels of glycogen not only had been restored to what they had been before the workout, but had soared past that point, increasing by as much as a 60 percent in the frontal cortex and hippocampus and slightly less in other parts of the brain. The astrocytes had “overcompensated,” resulting in a kind of brain carbo-loading.
The levels, however, had dropped back to normal within about 24 hours.
That was not the case, though, if the animals continued to exercise. In those rats that ran for four weeks, the “supercompensation” became the new normal, with their baseline levels of glycogen showing substantial increases compared with the sedentary animals. The increases were especially notable in, again, those portions of the brain critical to learning and memory formation — the cortex and the hippocampus.
New York Times: How Exercise Fuels the Brain
While many of us wonder just how much exercise we really need in order to gain health and fitness, a group of scientists in Canada are turning that issue on its head and asking, how little exercise do we need?
The emerging and engaging answer appears to be, a lot less than most of us think — provided we’re willing to work a bit. [...]
For years, the American Heart Association and other organizations have recommended that people complete 30 minutes or more of continuous, moderate-intensity exercise, such as a brisk walk, five times a week, for overall good health.
But millions of Americans don’t engage in that much moderate exercise, if they complete any at all. Asked why, a majority of respondents, in survey after survey, say, “I don’t have time.”
Intervals, however, require little time. They are, by definition, short. But whether most people can tolerate intervals, and whether, in turn, intervals provide the same health and fitness benefits as longer, more moderate endurance exercise are issues that haven’t been much investigated.
New York Times: How 1-Minute Intervals Can Improve Your Health