In the gym I go to, we don't have personal trainers but gym instructors - they just stay there and guide pretty much everyone if they have doubts or they see someone exercising incorrectly.
From what I know, there are 3 gym instructors. I always go to gym in the afternoon and I always meet the same instructor. He's a very cool dude and I have no personal problem with him, even though he is not actually my friend: I never have contact with him outside the gym.
However, he ALWAYS talks to me, from the moment I get there until I leave. I only have about an hour to train and since he is always talking to me, 95% of the time I don't get to finish all the exercises I should.
I have tried some non-direct approaches:
Going with earphones on: didn't work, he still talks to me and practically ignores that I am listening to music.
Giving short answers (trying to show that I am not inclined to talk): he seems not to notice that someone does not want to talk.
I don't want to be rude with him because again, he is a nice person and I don't think he does that on purpose. The subjects we talk about are not the problem either (just current events, chit-chat, not gym-related). The only problem is that I want to be able to finish all my exercises.
How can I express my willingness to be able to finish my workout, should it mean for him to talk less to me? I don't want to completely stop talking to him, but not that frequently.
The gym instructor and I are both males. I don't think he was romantically interested in me because I'm pretty sure he has a girlfriend (as I have seen him leaving holding hands with her). Even if that is not the case, I'm also heterosexual so I think I never gave him the impression I was flirting with him.