Did Kendo practicing helped Kirito in SAO? At the second season of Sword Art Online we can see Kirito and his sister practicing Kendo:

 

In this scene, he used a similar fighting style that he used in the game. Is it possible to say that practicing Kendo or other fighting sports could help people in Sword Art Online?
I mean, being strong or fast in real life, Did it have some influence in the gameplay at SAO?
If so, people like Kirito could have some advantage?
Haven't seen the anime, but at least according to the Light Novels, it is implied that Suguha was better than most other players in Alfheim due to her expertise in Kendo. So answer to your first question would be a yes. It also goes in the other way around, in that skills learnt virtually can be applied to the real world, though there will be limits based on one's physical attributes naturally.

In Kirito's case though he given up on Kendo a long time ago, as kids. His prowess probably came from his inborn reflexes and his belief that both the gaming and the real world are 'real'.