I think drumming doesn't provide enough stimulation to truly make one become substanially fitter.
Although it would be nice for the old ego to feel that drumming is on a par with the physical prowess of professional sports people in truth many a fat b@stard sits on the drum throne.
If you sit down then you are only waggling your arms and legs about rather than making the large muscles of your legs handle your body weight then how could this ever equal the performance level of a soccer player.
Although I play double kick and I do have to build up my fitness to pull off a show I get fit far quicker by going for brisk walks up and down the local hills than by drumming alone.
I think that it is possible to practice drumming to be like a strenuous work out. But in reality why would a musician practice their instrument beyond the performance level of being a drummer.
I may learn to play my songs faster than the required tempo or to increase my endurance to employ a technique through a physically challenging song but it is silly to over train too much.