Exercise is good for the brain. We know that. But most studies of exercise and brain health have focused on the effects of running, walking or other aerobic activities.
Now a new experiment suggests that light resistance training may also slow the age-related shrinking of some parts of our brains.
Our brains are, of course, dynamic organs, adding and shedding neurons and connections throughout our lifetimes. They remodel and repair themselves constantly, in fact, in response to our lifestyles, including whether and how we exercise.
But they remain, like the rest of our bodies, vulnerable to the passage of time. Many neurological studies have found that, by late middle age, most of us have begun developing age-related holes or lesions in our brains’ white matter, which is the material that connects and passes messages between different brain regions. 
For the new study, which was published this month in The Journal of the American Geriatrics Society, the scientists zeroed in on 54 of the women, whose scans showed existing white matter lesions.
The scientists tested the women’s gait speed and stability, then randomly assigned them to one of three groups.
Some began a supervised, once-weekly program of light upper- and lower-body weight training. A second group undertook the same weight-training routine but twice per week. And the third group, acting as a control, started a twice-weekly regimen of stretching and balance training.
All of the women continued their assigned exercise routines for a year.
At the end of that time, their brains were scanned again and their walking ability re-assessed.
The results were alternately sobering and stirring. The women in the control group, who had concentrated on balance and flexibility, showed worrying progression in the number and size of the lesions in their white matter and in the slowing of their gaits.
So did the women who had weight trained once per week.
But those who had lifted weights twice per week displayed significantly less shrinkage and tattering of their white matter than the other women. Their lesions had grown and multiplied somewhat, but not nearly as much.