The study looked at 135 women between the ages of 65 and 75 over the course of a year. The women were assigned one of three groups: group one took a one-hour resistance training class once a week, group two took a one-hour resistance training class twice a week, and group three, the control group, took a one-hour balance and stretching class twice a week. The women were all evaluated for a range of cognitive functions at the start of the study, at the six-month point, and at the end of the study (at the 12-month point).
The bad news is that strength training for six months, whether once or twice a week, didn’t lead to any changes. The good news is that if you stick to it for a year, you only need to train once a week to see an effect. After 12 months, the researchers found that all the women who underwent strength training showed a significant improvement in attention. The researchers evaluated attention using the well-established Stroop test (see image below), where the names of colors are written in an ink of a different color (for example, the word blue is written in red ink). To assess attention, the participants were asked to name the color of the ink (and not the word) as fast as they could (try it!). The once-a-week and the twice-a-week resistance training groups significantly improved on this task, while the performance of the balance and stretching group slightly deteriorated.
This improvement in cognitive function didn’t come without a price. The women in the once-a-week resistance training group complained of joint and muscle pains more than the women in the two other groups. It seems that the sweet spot for both an improvement in cognition and a lower risk of pain is to train twice a week (at least). This makes sense to me: the more frequently I exercise, the more my body gets used to the motions. It is also worth noting that the researchers tested other cognitive tasks such as memory and these didn’t show any change with resistance training.
Overall, though, I think this study is great news. I know that many older adults shy away from rigorous aerobic exercise (even young adults… *cough cough*), so this could be an easier alternative to help with brain health. And even if the “brain benefits” of resistance training could be a little more impressive (like by curing Alzheimer’s disease, while we’re at it), on the plus side, strength training also improves gait speed (your natural walking speed), and an improved gait speed is associated with a significant reduction in mortality. So if you don’t exercise for your brain, do it for your lifespan.
Reference: Resistance training and executive function: A 12-month randomized control trial. (2010) Liu-Ambrose T. et al. Arch Intern Med 170(2):170-8.