Here's a question I'm not really sure I want the answer to. But the thing is that I remember this from before the shin splints, and given this morning's run, it's come up again.
My current suspicion is that since the treadmill has a built in fan aimed at the upper half of my body, there's an evaporation induced temperature drop. That combined with my jostling shirt could cause problems. But why only the right?
Well hopefully I'll just get the point where I can take my shirt of jogging and not need to worry about it (or at least test the theory).
Oh, and I've fixed comments now.