I would suspect that this is a mechanical issue, not one relating to fitness.
With the forearm, I would expect there to be some mechanical flaw that adds excessive valgus stress to the elbow since the flexor-pronator mass helps to stabilize the UCL. Strengthening the forearm and fixing the mechanical flaw should help with this.
The bicep issue could likely be caused by inefficient deceleration. I have had this issue in the past and the direct cause was excessive stride foot flyout (im left handed and my landing foot was pointing towards the 3rd base line at SFC). Because of this, it was harder for my arm to decelerate, so my body relied more on my bicep, which caused some serious pain. The pain was gone the second I fixed the foot issue.
Just my opinion on the matter. Without seeing the mechanics, its hard to pinpoint what exactly is going on.