Exercise to me isn’t just about being physically active. I often have the thought “I need to go for a run to release some stress” and to me this demonstrates that working on the body’s muscles can actually benefit the brain too.
In fact, the brain itself is often described as being like a "muscle”. We repeatedly test the brain through memory exercises, such as exams, but rarely consider how physical exercise could test the brain too. For example - I wouldn’t expect to build my bicep muscles without being physically active, so why can’t my brain muscle be affected by exercise too?