noun, na-adjective, noun which may take the genitive case particle 'no'
tendency to get deeply absorbed; perfectionism; fastidiousness
Describes a personality trait of becoming intensely focused on a hobby, work, or detail, often to the point of obsession. Can be positive (meticulous) or negative (obsessive).
He has an obsessive streak and is absorbed in his hobby of model-making.
Because I'm a perfectionist, I want to finish every detail of my work perfectly.
susceptibility to stiff shoulders
Rare, literal meaning: a physical tendency to get stiff shoulders. In modern usage, the figurative sense (sense 1) is overwhelmingly more common.
The word 凝り性 also has an old meaning of a constitution prone to stiff shoulders.
He's the type who gets deeply into everything he does, insisting on getting all the right gear first.
My father gets obsessive about things, so he owns dozens of fishing rods.