Thanks Adam!
Day 4: pain in the neck and back has started healing, whereas I am still unable to move my arms...especially the left one, I think there might be a problem with some nerve or ligament indeed because it feels too strange (yes, I think numbness is the right word). Besides, I injured that arm in a landing a couple of years ago...it was nothing too serious, but it took a while and a lot of physiotherapy before ligaments, tendons and muscles completely recovered, and that could be the reason why the arm has been affected by the tunnel so much.
Well, at least today I can stand up, whereas yesterday was even worse than the day before
I definitely think I have to do some fitness training before I enter a wind tunnel again...