That was actually the only example I could come up with. I thought of posting one of those youtube videos of weightlifters breaking their elbows doing that, but decided I'd spare you all.
As for NFL linebackers, we totally see them stiff-arming the opposing linebackers all the time. Yeah, right.
If Chris H's diagrams can't even explain straight athletics, why are we still talking about them?
Who is saying your arms have to be straight? I am saying that you use less muscle if you fully align the bones. There are good and bad things about this. If you want to use the least muscle possible, the more the bones are in alignment the better.
This is my whole problem with not using skeletal alignment with the ground, and still use less muscle. You can't do both at the same time.