Hanging from a bar causes my bicep to feel much harder than when simply holding my arm straight above my head relaxed, without a bar.
This was slightly surprising to me: I used to assume that since the arms are straight during a dead hang, the biceps don't have to do work.
Are they under static contraction just to hang from a bar? Is it an effect of having to grip the bar, or would I observe the same tension in my bicep from being suspended at the wrists?
Why does this happen?