What to do in between studies?

Hi, I'm a college student, and I study at my school's libraries.

We have tests all around semester, so studying constantly can be very hectic.

I prefer 1 hour study-10~20 minute rest cycle, but I realized that toying with my iphone is only making my brain more tired and cramped.

Any suggestions of what I could do? Preferably, it should relax my brain(refresh, even) and it should be done in the time I mentioned above!

I usually do these three things to take a break from studying:

1) Play with my dog.
2) Talk to my mum.
3) Answer questions on Y! Answers!

Go for a walk in the fresh air.

I always go outside for a walk.