I just have a sports frame with cheap glasses. Sport frame = same as normal frame but with the little curling springs that wrap around the base of your ear.

The sport frame are flexible in the joints and can be bend back into shape without risking damage. These things are rather inexpensive and will take new glasses when needed.

I never had any troubles with these and I made some crashes in my time.

In the beginning I just used an old pair of glasses with a string that just fitted around my head. Or rather is was as band can of thing. Worked well for about 6 years, then I lost one glass in a major crash, but the frame was rather old be then over 15 years old actually. It was bound to die sometime.

Wouter