Physical traiining won't be part of your professional flight training course. As has been said, you'll simply be responsible for being able to pass a Class I each year.
When you start with an airline, you'll do some evacuation/emergency/survival training which will probably involve ditching/smoke in the cabin scenarios etc.
I can't see any massive advantage in doing extra training for this kind of thing - the tasks are doable by all pilots and cabin crew so you won't have to be a star athlete.
Improving your health and fitness is great - just don't expect it to have any bearing on job prospects or desirability! By the time you're doing the above training, you'll have signed the contract anyway.
V1R