The fitness market segment is, like the beauty category, usually a sub-category of the health segment in that they are closely related. Also like beauty, the two are very obvious as to what should be assigned to it and what should not.
Sometimes companies that might be expected to be in this category are otherwise assigned to recreation instead. This is because, generally, companies are assigned to a market segment as close to the one they claim to be competing in as we have (with the notable exception of technology). Thus, if a company makes more claims about fun and recreation than health and fitness, they are assigned over there instead of here.