Acute aerobic exercise to recover from mental exhaustion

> I was just now diagnosed with ADHD as an adult in my mid twenties. My diagnosis probably took so long because I've been "self medicating" with exercise for the last ~10-15 years.

Also, Jesus. It's as if ADHD is a manufactured diagnosis to pathologize a healthy response to living conditions humans should find intolerable: sitting at a desk all day. I won't link to Born to Run, but it's easy to see that pre-industrial humans (i.e. 99% of the homo sapiens lifestyle) had lives full of physical activity. We call exercise "self-medication" when it is really a sick society that we should address.

I also found that I work pretty well when under pressure or someone request something challenging (especially if it's a girl I like :D). However, both are external forces and they don't come very often. It's VERY difficult to find jobs that consistently provide enough challenge because those jobs are very picky about candidates. Neither often there is any request coming from other people.

It would be nice if I can grow an internal force.

There are three ways to slice this fact, depends on who you ask. And I've asked a lot of people, because India treated "sports" as the refuge of those who cannot cut it in academics & I had two decades of people telling me to "quit running around, sit and study" which I had to unlearn in my 30s.

First is that thinking is not just limited by the "hardware" / displacement of your brain engine, but the consumable for doing it - that when I go for a walk and kick up my heart to 130 bpm, my brain is getting the equivalent of a turbo boost (literally, more oxygen to burn). The same applies to the glucose out of the liver, where a runner trains to feel the second wind coming even when the thing burning through glucose is their brain. And I've found that I can burn through a lot playing chess - heart-rates up by +30, extremities go cold and hunger stops when I'm thinking hard (or losing). Lower your heart-rate sitting still, the more boost you can push when needed.

But there's also a problem with selection bias.

Second is that running or endurance sports is not entirely physical. Nobody is chasing you to run, you are running on pure internal motivation & that selects for people who are good at staying on a chase. The mindset needed to keep running 10+ miles is basically why we tell people "this is marathon, not a sprint" when it comes to putting in time into something new. Because the mindset is about pacing, not absolute pace (the swimming scene in Gattaca comes to mind). I think this is selected for but like muscles it grows with use; you can evolve your mindset closer to being a persistence predator of ideas, beyond boredom.

Third is that the resources needed to be an amazing endurance runner and a PhD candidate are correlated - you need to focus away from paying the bills and work on doing something which has a slow burn with a very delayed reward. You need a healthy childhood, you need time to go running and you need a culture which values physical fitness as either a military tool (the himalayan hikes I went to were full of israelis in their 20s) or social status symbol (a somewhat post-scarcity economy).

I can't run as fast or in competitive fashion, a half marathon is my distance of choice, but I running for the first two reasons and can keep doing it for the third.