Are there any challenging upper ab exercises? I've been doing crunches all different ways and now it's just too easy. I've even added weights and it's too easy. I guess add more weights?
Anything with your arms overhead. Like throwing a medicine ball to someone with your arms straight/overhead while laying back on a stability ball, or crunches with a weight held overhead, standing ab pull downs with your back against a solid surface.
Honestly, I'm not sure why you'd just want to hit the upper abs, but I thought I'd try to answer your question anyway.
I do a variety of ab exercises - I use a decline bench with the med. ball, lifting up, I also do crunches, leg lifts, and I also use the roller - just a variety to hit all parts of the abs.