Don’t stick to just one type of exercise, like aerobics, to build your brain cells. A 2016 study showed a correlation between weight training and dramatically improved cognitive function in a group of older adults suffering cognitive decline. Stretching exercises alone didn’t help. Most health specialists say thirty to forty minutes of weight training a week is sufficient to maintain optimum health. Weight training can vastly improve muscle strength, balance, and flexibility—all of which are good for your brain.