Well , yes stretching in severe pain stage will lead to more flare up because you are stretching nerves too not only muscles , the pain is just protective reaction toward the the stretching .
I would prefer complete rest with some simple mobilization exercises for the nerves around cervical , scauplae and shoulders , assurance , breathing ex.s ,Education espicially regarding sleep , behavioral and cognition therapy is really of value in this stage .
What do you mean by kayakers ?
cheers
Emad