Most of us know that if we don’t exercise our muscles, they get flaccid and weak. What most of us don’t fully know is that physical exercise also keeps our brain in better shape. Doing mental exercise is important, such as working crossword puzzles or Sudoku, but physical exercise is critical to vigorous mental health also.

Science has taught us that the old dictum, "You can’t teach an old dog new tricks," is not true. The older brain is much more plastic and teachable than is commonly known. Although older adults generally learn new things more slowly than young people, they still can improve their cognitive functioning with some effort, delaying the declines in cognition that comes with advancing age. A better dictum than the "old dogs" one was coined by our second President, John Adams, who said, "Old minds are like old horses; you must exercise them if you wish to keep them in working order."

Scientists and philosophers have been studying how to keep our minds vibrant for centuries. Most recently, Karlene Ball of the University of Alabama has found that cognitive training in the areas of memory, reasoning and visual search helped a large sample of individuals over the age of 65 significantly improve their abilities on these tasks over those who did not receive the training. These improved skills persisted for many years.

Physical exercise may be even more important than mental training in sustaining cognitive functioning over the years. Kristine Yaffe at the University of California in 2001 studied women over the age of 65 for six to eight years and found that the most active women had a 30 percent lower risk of cognitive decline. Interestingly, walking distance was related to cognition, but walking speed was not.

Even better, aerobic exercise and toning your circulatory system improves brain fitness. In 1995, Marilyn Albert of Johns Hopkins University found that strenuous activity and peak pulmonary expiratory flow rate among 70 to 79 year olds was the best predictor of cognitive efficiency in the areas of verbal and non verbal memory, language, conceptualization and visuospatial ability. In younger samples, Marcus Richards of the University College London in 2003 reported that physical exercise and leisure-time activities at age 36 was associated with higher performance on memory tests at ages 43 to 53 years.

Dementia, an illness of declining cognitive functioning in later years, was studied by Suvi Rovio in Sweden in 2005. This study found that physical exercises that lasted 20 to 30 minutes daily and caused breathlessness and perspiration in people of middle age gave them a 52 percent lower odds of having dementia than a comparable sedentary group at ages 65 to 79.

Other factors are associated with improved cognitive functioning in later years, such as having a vibrant social life. A positive attitude also seems to be important, but it may be that it is the positive attitude that influences other health related behaviors related to improved cognition more so than just the positive attitude. But why take the chance? Keeping a positive attitude toward yourself and supporting healthy exercise, both mentally and physically, will help see you into your later years with a mental sharpness you most likely wouldn’t have leading a sedentary, socially isolated lifestyle.