The cut fastball

Is this pitch stressful on the arm?

Thrown correctly no. Thrown incorrectly you can get some problems. Sometimes this pitch is such a nice pitch you begin to turn over the wrist which isn’t good. You don’t want to do that. If you throw it correctly just like your fastball it’s harmless.

It’s very much mental think fastball when you throw this. Same everything just like your fastball and combined with a good change-up theres 4 pitches including your 2 fastball that all look the same.

It’s not bad for your arm(elbow/shoulder) but it can cause forearm stiffness. This happened to roy halladay when he over-used his cutter.

I agree.

If you feel any pain at all STOP throwing the cutter then see if it goes away after a week or so then if the pains gone you can work on throwing it correctly. If the pain stays you have some more problems on your hand.