GROWING up in the Netherlands, Henriette van Praag had always been active, playing sports and riding her bike to school every day. Then, in the late-1990s, while working as a staff scientist at the Salk Institute for Biological Studies in San Diego, she discovered that exercise can spur the growth of new brain cells in mature mice. After that, her approach to exercise changed.

“I started to take it more seriously,” said van Praag, now an associate professor of biomedical science at Florida Atlantic University. Today, that involves doing CrossFit and running eight or 10 kilometres several days a week.

Whether exercise can cause new neurons to grow in adult humans – a feat previously thought impossible, and a tantalising prospect to treat neurodegenerative diseases – is still up for debate. But even if it is not possible, physical activity is excellent for your brain, improving mood and cognition through “a plethora” of cellular changes, van Praag said.