Bast, there is no strange circular depression... I finally realised what the hell you've been talking about and why you only noticed it on the Left...

You've been rendering this entire time with poser's default lighting, where the primary light source is on the left side of the screen. This causes the shadow to appear on the left but not the right in your poses. Try it with a more uniform lighting set and you'll see what I mean.... as in the attached picture. the light set here applies light equally to both left and right sides...

Now, find anyone with a build similar to default Mike3 and ask them to hold their arm out... take a good look at the not-so-strange circular depression in between the Brachioradialus on the outside of the forearm and the muscles on the opposite side (inner arm)... Notice the depression? I can tell you flat out, it's not an oddity, that's all you. I am built very similar to Mike 3, and I have that same strange circular depression in my forearm... and so do a lot of people I've looked at. It's the depression that naturally exists in between the two muscle groups.