There's no shortage of information available about the benefits of exercise for the body - it improves cardiovascular fitness and circulation, builds lean muscle mass and reduces body fat, and aids in building strong bones, to name a few. But what about the brain? Especially as we age? As the last of the western baby boomers have begun to creep into their 50s, scientists have begun to study the hows and whys of ageing. What many researchers have discovered is the dramatic difference in the physical condition of brains between those who are physically fit and those who aren't. It used to be thought that the brain slowly degenerated as we aged. Now, scientists know there are many triggers that make parts of the brain regenerate themselves. One of these triggers has been linked to how fit you are because it's believed that exercise causes an increase of oxygen-rich blood to specific parts of the brain. Duke University, in the United States, conducted a 16-week study that had volunteers exercise three days a week. Following this programme, the subjects' memories significantly improved and they were able to juggle tasks more easily. But it's also been found that the type of exercise undertaken may be an important factor for improving brain power. In 1999, the Beckman Institute at the University of Illinois in the US took a group of 124 older, healthy adults and gave them memory tests before splitting them into two groups - one doing aerobic activity (three 45-minute walks a week) and the other stretching and toning exercises. After six months, the subjects were given the same cognitive tests. The walkers improved their scores by 15 to 20 per cent. The stretchy group had more flexible bodies but didn't improve their memory scores. Researchers in Japan have found that the brain functioning of people under 50 may benefit even more than that of their older counterparts. They took seven subjects between the ages of 20 and 40 and had them run for 30 minutes two to three times a week for at least three months. All of the runners significantly improved their scores on the memory-skills tests they had taken prior to the study. But these improvements lasted only as long as the training and fitness did. Once the runners stopped training their test scores fell. Other studies agree. Researchers from the University of Illinois say you need at least four months of consistent, moderate cardiovascular exercise to begin to show a reduction in the amount of brain tissue you lose. And by losing less brain tissue, it's now believed that memory loss is reduced. Weight loss can also improve your memory because dropping the extra weight improves how your body regulates glucose. And since your brain can only use glucose as energy, this can cause your brain to function better, improving your memory. One more tidbit in favour of exercise: researchers at the Salk Institute in California have discovered exercise stimulates the formation of new brain cells in mice. Considering that a few years ago it was an established medical fact that human brains never generate new neurons, this is quite remarkable. So there's even more reason to exercise.