Slow things down and get a deep core workout with this variation on the traditional bicycle crunch. It adds resistance for a bigger burn.

Mix and match for 30-second holds, and feel the full-core power kick in. Bicycle crunches give your abs and obliques a ...

No matter which variations you follow, crunches have the advantage over sit-ups of being able to better target abdominal muscles. "Because the movement is smaller, you can control momentum more," ...