Would striding open for a righty (if there was a straight line going from the mound to homeplate and your foot landed way to the 1B side than normal) cause soreness in the area where your forearm connects to your bicep if you were holding your hand with your palm to the sky?
not sure if the mechanics are causing this but try to strengthen the forearm. do wrist curls and wrist turns. that part of the arm gets sore because when you release those muscles need to tighten up to protect the elbow. so just try to strengthen the forearm.
I don’t think it would be very healthy to stride a great deal open to the first base side.
If you’re striding in one direction and trying to throw the ball in a different direction, then you’re directing your energy in a direction that is different from the direction you’re trying to throw the ball. Plus, you’re probably opening up the hips early and wasting energy created by the lower half. Given all of this, you’re most likely going to ask the arm to compensate and that’s going to put extra stress on the arm. It’s not surprising that it is causing you a sore arm.
There is literature out there on this and studies have shown an open stride and open foot orientation, relative to the plate, increases the stresses on the arm. I believe it was a study by Escamilla and Fleisig.