Box crunches, oh how they burn!! I went looking for a video to share that demonstrates them, but I was fairly unsuccessful finding one. Maybe they are called something different.

I do them on my kitchen counter and extend my legs out until they are straight (and much faster than this guy). I did sets last night until muscle failure and am feeling it today for sure. They are a great variation to the ho-hum core exercises.

Do you have a secret weapon exercise for targeting the core?