Here's a potential benefit to add to the long list of reasons for why we should always stay active: exercise could increase the number of neurons in the brain. Scientists in Finland report that when groups of rats were given strict exercise regimes, some of them developed new brain cells at a more rapid rate than their less active peers.

The catch? This heightened rate of neurogenesis only occurred with certain types of exercise. The researchers found that moderate aerobic exercise produced new cells in the brain, while strength exercises didn't (despite giving the rats a more toned physique). If the same is found in humans, it looks like a daily jog can be better for your brain than a weight-lifting session.

The benefit of neurogenesis - or the growth and development of neurons in the brain - is that it helps memory and learning processes. This growth is most noticeable while we're still in the womb, but it continues into adulthood to a lesser extent as well. The opposite process, where brain cells are lost, is also a natural and expected one, but can ultimately lead to diseases such as Alzheimer's later in life.

Researchers from the University of Jyvaskyla split their rats into three groups with three different exercise programmes: moderate running, weight-lifting, and high-intensity interval training.

The running rats were given a treadmill to use, while the weight-lifting rodents were trained to climb a ladder with weights attached to their tails. The 'joggers' were found to have significantly increased levels of adult hippocampal neurogenesis (2-3 times more) than either of the other groups, plus the sedentary control group.

Why was high-interval training (HIT) not as effective? The team thinks the extra stress involved in those particular exercises may have limited the benefits in terms of brain cell formation. They also point out that strength training may well be good for your brain too - just not in terms of the variables measured in this study.

What's more, genetic predisposition to aerobic exercise seemed to have an effect on the end results: in other words, the rats that were naturally suited to running showed higher levels of neurogenesis.

While the exercise types were chosen to fit the same programmes we might set up for ourselves, there's no firm evidence yet that the same kind of neurogenesis happens in humans - although previous studies have certainly hinted at it. Lead researcher Miriam Nokia plans to continue looking into the effects of anaerobic training on the brain, but in the meantime, you've one more reason to fit a daily run into your schedule.

The group's work has been published in The Journal of Psychology.