In a landmark randomized trial, 120 older adults either walked briskly for 40 minutes three days a week or stretched for one year.

The walkers’ hippocampus, the brain’s memory center, grew by about 2%. In the stretching group, it shrank. That’s equivalent to reversing one to two years of age-related brain shrinkage.

Those whose hippocampus grew the most also showed the greatest gains in memory.

No prescription, no special equipment required. Just a brisk walk.

When was your last one?

Study: doi.org

https://www.pnas.org/doi/epdf/10.1073/pnas.1015950108

This is Erickson’s 2011 PNAS study on walking, a well-known landmark paper. The brain finding holds up, but the memory claim in the title goes beyond the data.

What it found: 120 adults, about 66 years old, were randomized to either brisk walking (40 minutes, 3 days a week) or stretching for a year. In the walkers, the hippocampus, the brain’s memory center, grew about 2%. In the stretching group, it shrank about 1.4%. That works out to turning back roughly 1 to 2 years of age-related shrinkage. Walkers whose BDNF rose more (BDNF is a protein that helps brain cells grow) also had greater hippocampal growth.

Strengths: It was randomized, lasted a full year, used MRI at three time points, and walking was supervised.

Caveats: Memory improved about equally in both groups, so walking didn’t outperform stretching on the memory test itself. The link to memory is correlational: people whose hippocampus grew more remembered better. 179 people enrolled, but only the 120 with complete scans were analyzed. The study is also 15 years old and hasn’t always replicated cleanly.