Jonathan Wiggs/Globe Staff

Christopher Muther worked out with master trainer Albert Samano at the Boston Sports Club.

Jonathan Wiggs/Globe Staff

Muther realized after three years of training, Samano had become one of his closest friends.

Jonathan Wiggs/Globe Staff

Muther appreciated everything that Samano has taught him about fitness. But just as much — if not more — he appreciated his friendship.

Jonathan Wiggs/Globe Staff

It’s not unusual for trainers to bond closely with their clients, inside and outside of the gym, both trainers and clients have found.

Jonathan Wiggs/Globe Staff

“If I don’t have that bond, then I’ll switch trainers,” Melissa LaGrant said. Above, LaGrant with Equinox trainer Jeff LaJoie.