fitter
Definitions
A person who puts together or installs machinery or equipment.
A person who fits garments, such as a tailor or dressmaker.
Comparative form of fit: more suitable, healthy, or in better physical condition.
Examples
I have been going to the gym every morning to get fitter for the upcoming marathon.
The new employee is a much fitter candidate for the role than the previous applicant.
After months of consistent training, he feels significantly fitter and more energetic than he did last year.