What is fitness?

Fitness is the condition of being physically fit and healthy. Not necessarily being able to run for long periods of time but being fit for the sport you play.

For example, this sumo wrestler is classified as fit in his category of sport. You have to be this big to be able to be suitable for sumo wrestling. Being fit is not always being skinny and lean.

And as for this gymnast, he is classified fit for his sport, he has to be able to lift his own body weight.