I'm not very flexible -- too much time in front of a computer -- but 'boarding should be good for me to loosen up my body and stay limber. (I'm having a tough time so far -- even though I bought a good, stable longboard.
I like that 'boarding offers a full-body workout. It requires me to move arms, legs, and feet. That twisting motion is what I like compared to biking. (I'd run but my knees are creaky :)
Also, I like that I could do it all day and increase my physical stamina. With the right 'board, you could skate for miles with a crusier. See A Longboard Brand Buyers Guide to learn about choosing a board for endurance.
I don't do many tricks. (I got a longboard, not a skateboard.) But I do know that the small amount of tricks I can do have increased my precision.
All the small movements require me to place my feet on different spots on the board or adjust my timing or speed before doing the trick. Mostly, it's taught me that I still suck.
My coordination is getting better, though. If I wasn't an old codger, I think that riding a 'board provides a youngster with some valuable tips: Learning consequences.
Riding is dangerous -- ever see skateboards try to gap a set of stairs and fail? Yeah, it's not pretty.
We learn that when we take risks, we have to suffer the consequences of those risks. Sometimes, that means broken bones and nasty rashes from crashes.
All these oopses result in increased coordination, strength, balance, character and less accidents because you learn to crash. It sounds crazy. But I learned how to crash years ago while riding mountain bikes. I wrecked my bike for about a year straight. During that time, I learned how to crash and minimize damage.
Now, I'm not as limber as I was when I picked up longboarding, so I made sure to not get a skateboard (I needed something stable) and I made sure to read up on how to make a stable longboard.
I found these resources very helpful: Longboard Buyers Guide. >>Newbie Resource Guide<<, What are the Best Longboard Trucks on the market?, Tips for Getting the Best Longboard Wheels, and What Are the Best Longboard Bearings for You?
I also like physical activities for reliving stress. It helps me detune and just chill out. I also feel much better because it is a physical exercise.
I'm sure it helps with other health problems like high blood pressure and obesity but I don't know too much about medical health. But my favourite thing about riding is that it burns calories.
Granted, those who are skateboarding in pools and pits are burning a lot more than me. However, I'm still getting a workout.