I recently restarted cycling to work. I did four round trips. After riding back from the fourth trip, my stomach muscles started to tense and cramp. 

I heard that stretching before and after a ride, as well as remaining hydrated, could prevent this. Is there anything else I could do to prevent cramps? I intend on riding four days next week too because of the lively feeling I gain from cycling.

**EDIT**

There is nothing abnormal about my medical circumstances.

I ride 9mph on average in one direction (using cycle paths rather than roads) and slightly less coming back.

A one-way trip is under four miles.