This is an interesting correlation: Bigger muscles lead to a bigger, healthier and younger brain. The research was focused on preventing cognitive decline and the development of dementia in older adults. It followed 100 people aged 55 to 86 as they pursued a specific fitness regime, measuring the effects on their brains through tests and MRI scans. After six months of training the subjects showed not only improved cognitive function, but even growth in key areas of their brains. The exercise? A simple regime of weight training, that involved lifting weights that were 80 percent of the maximum they could handle twice a week.