I don't think there will be any contradiction. After all, everyone has his own hobbies. Men and women in love don't have to have the same hobbies to make their feelings stronger. Your girlfriend likes fitness, which shows that she is very demanding and self-disciplined. She pays more attention to her external image and health. This is a good interest!
Girlfriend likes fitness. As a boyfriend, you should actively support her such a hobby. Although you don't like sports, you can praise and affirm your girlfriend. If you don't like to take part in fitness, you can do other things you are interested in, and your girlfriend won't object! But for the sake of health, I suggest that you can accompany your girlfriend to participate in some fitness activities, after all, it is good for your health!
Your different interests and hobbies will not affect the intensity of your love at all. As long as you care more about each other and show more love in other aspects of life, your love will make your girlfriend feel happier, so your feelings will grow stronger and stronger! Men and women in love should learn to seek common ground while reserving differences, treat their other half with their own sincerity and be absolutely loyal to their feelings. This kind of love is more practical and happy!