Is there a good alternative to crunches?
 

All workout routines should focus on making your core stronger and more stable. But don't stop what you're doing and perform 100 crunches. Planks, Hollows, Superheroes, and Stability Work are safer ab workouts and much more effective alternatives to crunches for strengthening and stabilizing your core.

https://www.youtube.com/watch?v=A4zAHBHWDKg