Exercise is good for your mental health. But there’s a difference between walking the dog for exercise and competing in Ironman triathlons for exercise. How much exercise do you really need for a brain boost? So far, studies into the matter have been small and hard to generalize from. When it came to how much exercise a person needed to see the biggest mental health benefits, it turned out that more wasn’t better. Here’s a graph of the relationship between amount of exercise and the number of bad mental health days someone had. The dashed lines indicate 3, 4, and 5 days a week, respectively. You can see that as exercise frequency increases, mental health burden decreases — up until a point, when mental health gets worse again. Something similar happens with exercise duration. According to the researchers, the sweet spot is right around 30–60 minutes three to five times a week (or 120–360 minutes per week, total). Any more or less, and the brain benefits wane.