Is it safe to do a thousand sit-ups a day?

Bravo. Sure it is safe, but it may cause some soreness. I think one day I did around 400, and that was okay for me. 1000 is quite a feat.

Its safe, though who would be able to actually accomplish 1000 sit-ups?

i did about 300 a day and develop a raw spot on my rear.

very negative experience and a pointless waste of time.

i know better now.

but maybe it will be a positive experience for you.

just do a 1000 a day and find out.

Safe yes

Probably horrible for the back

Overtraining is pointless

It's safe but your gonna be really sore and for really no reason unless you do it everyday which I don't recommend.

Pointless. Would you do 1000 biceps curls? Ab muscles are just muscles like any other.

Not only unsafe, but not necessary. Execution is primary: a few slow sets are more beneficial than killing yourself risking injury.

Something is going to break sooner or later.

Pointless, but safe if you have no injuries.

yes