I'm an occupational therapist. So I don't do the research, but I read a lot of it and apply it to problems in real life.

Exercise like you mentioned improves cardiovascular health, and more oxygenated blood moving through the body has all kinds of benefits, including for the brain.

But the brain needs more than oxygenated blood, it needs stimulation. Let's say you chose to run the treadmill three times a week. You'll get the obvious health benefits. But will it make you more assertive the next time you are confronted at work? Will it teach you to solve problems by being proactive, instead of avoiding issues until they grow too big to ignore? I say no.

Yet I've had these benefits from Aikido, and I know that this is because Aikido provides:

Moderate to intense vestibular input - arcing, rolling, spiraling through three-dimensional space. This input has a strong effect on attention and alertness, and increases the brain's ability to take in information without becoming stressed. Stimulation lasts about 8 hours. If you never roll, tilt in space or go upside down, your brain is starved of vestibular input.

Moderate to intense muscle and joint input - this has the greatest effect on self-confidence and mood, as well as body mapping and coordination, especially if you are getting enough vestibular input. Lots of people know about this and lots of sports provide it.

Close physical contact with people - even though I know scientifically that we need this, I shy away from it as more of an introvert. You can get physical contact with people in any martial art and many sports, but not all. I always pursued solo sports before this. This was intentional; close physical contact with people is not necessarily pleasant, especially in competitive sport when you aren't very good. There is something unique about working with a partner who matches your movements, challenging and supporting you at the same time. I think that is unique to traditional martial arts, and dance. I did dance, but hated partner work. The difference for me? Dancing with a partner and feeling awkward, it's easy to think "why am I doing this?" Starting Aikido with a partner and feeling awkward, there isn't much time to think. They're about to hit you, so you move. Then they literally show you how to throw them to the ground. If I could've thrown my dance partner down each time I got frustrated, I might have stuck with it.

I would never argue that Aikido is the only way to get certain benefits or even the best, as I think that's an individual choice. But I do think it is uniquely suited to improve who you are as a person (physically and mentally) and how you are in the world. That is because it provides this range of vital sensory input to the body, not least of which is a network of people who want to challenge you, not defeat you.