these are notoriously bad for people who have lower back/nerve problems. Crunches give you the same benefit to the rectus abdominis, while being much better for your back and/or butt. Planks are also a better option, if you can do them without any arch in your back.
I recently switched to doing mine like this
(see curl-up). Incidentally, the whole set there is my new daily 6-minute routine.
I'm pretty sure you're both correct. I like your suggestions, although side planks are hard when you have bad rotator cuffs.
Try the side planks on an outstretched arm. Really good for shoulder stabilization for those among us with oft-repaired rotator cuffs. Much less shoulder stress than the forearm variety. Keep a nice straight form.
Will have to work on the straight arm side plank. Can't bend my wrist back far enough to rest on palm -- do push ups on my knuckles or fingertips. But can't do a side plank like that.
Do push ups grasping a bar bell. Try the side plank over a Swiss ball with the ball in your arm pit. Then raise and lower your butt or just hold. Same affect as using an arm.
Or just don't do side planks?
Looks like an opportunity to work on wrist flexibility. I had a fair amount of work to do on it after I shattered my wrist in 2011. Not perfect now, but enough certainly to do a pushup. Or at least that is not the limiting factor in my ability to do pushups.