Harvard: does Physical exercise sharpens the brain?

Apparently until this study there had been no hard evidence that being physically fit increases brain function. Other than the so so lame indications from trained rodents in the labs(I'm curious to know how they figured the rats got smarter, even better how they got the funding-I think the roaches in NY are smarter, any money for research?... So know this you can confidently rush out to the gym and give your self one more excuse to work out. Or one more excuse to be mad at yourself for not hitting the gym. This was published in the Journal of Gerontology. I am guesting that the readers are smarter than I am and know what 'Gerontology' means;)

"physically fit subjects had less age-related brain-tissue shrinkage than less active subjects. Using magnetic resonance imaging, the researchers saw clear differences in the frontal, temporal, and parietal regions of the brain"

see research below:

https://www.health.harvard.edu/newsweek/Physical_exercise_sharpens_the_brain.htm