His Kind of Perfection (Harlequin Super Romance, 1952)

A very personal trainer… 

Personal trainer Bree Rice is happy to help Kale Barlow get in shape to win back his ex. Kale's drive and enthusiasm make him the perfect client. He's such a great guy, it's easy to be his friend, too. All too soon, though, their friendship develops into something deeper…something off-limits. 

Bree knows love and work don't mix—been there, felt that heartache. But it doesn't seem to matter how many times she reminds him of his original goal. Kale is nothing if not determined, especially when it comes to convincing Bree that they are the perfect partners, both in and out of the gym.