ive heard of old men injuring their back and then popping wood for the first time in decades
something about a stimulant nerve crossing at a certain junction on your spine, causes the axon to fire constantly sending dick hardening signals to the dendrites of the targeted cells
Don't really know why, but when I had my accident ( which my back was broken ) I was out cold, but the paramedics knew my back was broken by my " stiffy " .
Who would have known? Don't ask me why they check that, but I guess its something that just happens.
I would not suggest breaking your back just to get a woody.