Grunting, breathing hard and sweating makes you smarter

Grunt pant exhale grunt uugh grunt exhale. Pump that iron!

That's all you really need to know.
So get with it! Get to the gym and start exercising!

Actually, it seems that aerobic exercise was the beneficial form of physical activity. The researchers next step is to determine what forms of activity are the best for avoiding memory loss.

Here's some details from the CNN article:

Exercise boosts brainpower by building new brain cells in a brain region linked with memory and memory loss, U.S. researchers reported Monday.

Tests on mice showed they grew new brain cells in a brain region called the dentate gyrus, a part of the hippocampus that is known to be affected in the age-related memory decline that begins around age 30 for most humans.

The researchers used magnetic resonance imaging scans to help document the process in mice -- and then used MRIs to look at the brains of people before and after exercise.

They found the same patterns, which suggests that people also grow new brain cells when they exercise.

The concept behind this research has its roots in research done at my institution UIUC. Here's an abstract from an older article with very much the same message:

Cardiovascular fitness is thought to offset declines in cognitive performance, but little is known about the cortical mechanisms that underlie these changes in humans. Research using animal models shows that aerobic training increases cortical capillary supplies, the number of synaptic connections, and the development of new neurons. The end result is a brain that is more efficient, plastic, and adaptive, which translates into better performance in aging animals. Here, in two separate experiments, we demonstrate for the first time to our knowledge, in humans that increases in cardiovascular fitness results in increased functioning of key aspects of the attentional network of the brain during a cognitively challenging task. Specifically, highly fit (Study 1) or aerobically trained (Study 2) persons show greater task-related activity in regions of the prefrontal and parietal cortices that are involved in spatial selection and inhibitory functioning, when compared with low-fit (Study 1) or nonaerobic control (Study 2) participants. Additionally, in both studies there exist groupwise differences in activation of the anterior cingulate cortex, which is thought to monitor for conflict in the attentional system, and signal the need for adaptation in the attentional network. These data suggest that increased cardiovascular fitness can affect improvements in the plasticity of the aging human brain, and may serve to reduce both biological and cognitive senescence in humans.