Questions & Answers about После долгой прогулки у меня болит нога и плечо.
Because of the preposition после.
In Russian, после (“after”) always takes the genitive case.
- Nominative (dictionary form): долгая прогулка
- Genitive (required by после): долгой прогулки
Both the adjective and the noun change to genitive feminine singular:
- долгая → долгой
- прогулка → прогулки
So После долгой прогулки literally is “after of a long walk,” which is just “after a long walk” in normal English.