Gretchen Reynolds in The New York Times:
So for the new study, which was published this month in the Journal of Physiology, researchers at the University of Jyvaskyla in Finland and other institutions gathered a large group of adult male rats. The researchers injected the rats with a substance that marks new brain cells and then set groups of them to an array of different workouts, with one group remaining sedentary to serve as controls. Some of the animals were given running wheels in their cages, allowing them to run at will. Most jogged moderately every day for several miles, although individual mileage varied. Others began resistance training, which for rats involves climbing a wall with tiny weights attached to their tails. Still others took up the rodent equivalent of high-intensity interval training. For this regimen, the animals were placed on little treadmills and required to sprint at a very rapid and strenuous pace for three minutes, followed by two minutes of slow skittering, with the entire sequence repeated twice more, for a total of 15 minutes of running. These routines continued for seven weeks, after which the researchers microscopically examined brain tissue from the hippocampus of each animal.
They found very different levels of neurogenesis, depending on how each animal had exercised. Those rats that had jogged on wheels showed robust levels of neurogenesis. Their hippocampal tissue teemed with new neurons, far more than in the brains of the sedentary animals. The greater the distance that a runner had covered during the experiment, the more new cells its brain now contained. There were far fewer new neurons in the brains of the animals that had completed high-intensity interval training. They showed somewhat higher amounts than in the sedentary animals but far less than in the distance runners. And the weight-training rats, although they were much stronger at the end of the experiment than they had been at the start, showed no discernible augmentation of neurogenesis. Their hippocampal tissue looked just like that of the animals that had not exercised at all.
More here.
