Questions & Answers about После долгой тренировки у меня заболела спина.
Because после always requires the genitive case.
- тренировка → genitive singular тренировки
- долгая → it must agree with тренировка, so it also becomes genitive singular feminine: долгой
So:
- после тренировки = after the workout / after training
- после долгой тренировки = after a long workout
This is a very common pattern in Russian:
- после урока = after the lesson
- после работы = after work
- после долгого дня = after a long day