When I do chin ups on about the seventh or eighth rep I experience a great neck pain. The pain tends to be located all through my neck and with a headache. As far as I know I am doing it with good form and breathing properly. I am also not overly exerting myself as I can do more, it's just too painful.
EDIT: I also experience a slight nausea and dizziness.
EDIT: I also experience a slight nausea and dizziness.