Client Testimonials?

[thetvirus513]

I am filming some short videos for a fitness studio in the area. among other things required is filming trainer interviews and client testimonials/workout sessions. I have the interviews down as those arent too tough, but how should I do the client testimonials? It is basically a very short interview but should I put a lav mic on them? should I just do it right when they are done working out in front of equipment and whatnot or should I bring them to the place where I do the trainer interviews and sit them down? I want the trainer and client interview/testimonials to look different, since they are different, but what would you guys recommend? any help is appreciated

Thanks!