i like to train freee throw, when some of my player still ahs skill below 5 - stamina training is a think i didn't like because i didn't notice the influence of it with the exception of the player rating.
Wich should be the way that you would prefer to noticed it? Training stamina is not going to transform a regular player into a superstar. Nor will make to train a specific skill for once.
Probably, a long term plan of Stamina Training Managment will decide it. "Regular" stamina as most of teams, a middle-down one or a high impact plan is going to shape the overall performance of your players.
Off course, when it comes to performance there is always this sort of trade off between training Stamina and a specific Skill. It is your call to decide it.