ADHD is a dopamine deficit disorder.
When someone is deplete in Dopamine, one finds ways to pump it into the areas of brain needing it desperately to keep your attention intact on the environmental stimuli and your inner environmental needs (conscience, morality, daily chores, routines, hygiene etc..).
Eating, rewarding with positive comments/ gifts, sex, any thrilling activity as well as physical activity pumps in your innate dopamine. That’s the sad reason why children remain hyperactive to keep their focus on tasks and activity of daily living intact. Not because they want to be naughty, but actually they are trying very hard to focus on what you are instructing them. I recognise the same pattern in parents when I’m giving a ‘long talk/ advice session’ on ADHD strategies, when they start to jerk their legs in a fidgety manner as if trying hard to listen (and I know where the chikd’s ADHD has come from).
This is effectively used in class rooms as movement breaks, fidgety toys, wobble cousins etc etc where some activity- discreet or obvious keeps this action in brain going.
Hence a run three times up and down the stairs before doing homework, walking to school or staggering physical activity with mental activity promotes learning episodes.