This is one of the times when we pause to question priorities. The symbolism you refer to does exist, yet what makes it any sort of priority to you? This I would leave as a rhetorical question. Additionally, we cannot necessarily translate rural African custom and implication so directly; depending on where one is in Africa, or anywhere else in the world, such behavior can have different meanings. Then again, if one insists on sexual focus, Jomo Kenyatta's Facing Mt. Kenya is essential reading, as is Norman O. Brown's summary of Freudianism, Life Against Death: The Psychoanalytic Meaning of History. Also remember the question of thrills; there are perhaps two in play in a Western setting we might pause to consider. There is the sexual, but there is also that of the forbidden, and in modern Western cultures blending the two is nearly inevitable. I cannot, for instance, account for certain behavioral changes I observe in my daughter; her aunt and grandmother―on my side of the family―were hounding her last weekend with the words "bra and underwear" in the wake of an apparent post-Edwardian meltdown at the prospect of actually shopping for underwear. And while there are certain inevitable processes occurring in both mind and brain at the root, the specific shame results from propositions of the forbidden, the taboo, from her maternal grandparents; this is a result of overaccentuation of sexual purity expectations and principles, which in turn results from the grandparents' own neurotic messes―i.e., a matter of priorities. It might be that you don't recall much literature on the subject because it wasn't there. While the fetishization certainly exists, like many others it emerges more apparently in the information superhighway; rare pornographies now have astoundingly deep libraries on sites around the world, and girls flashing while doing cartwheels is a genre unto itself that is further divided into subcategories. Comparatively, this one is understandable in its basic form. The taboos involved are the same reason we have cheerleaders in short skirts, and seem the only reasons men watch women's ice skating or tennis. And there is an identifiable phenomenon by which society seems to find excuses to allow and even encourage taboo behavior; compare a lady's responsibility to her skirts with the expectations toward a female cheerleader―they are inherently incongruous, but people can invent special occasions to license anything. But in the case of young girls turning cartwheels in the park, I would indeed look to your own priorities. Nor does this imply pedophilia or anything specifically dark. Nostalgia is powerful; I remember being a young boy and thrilling at a glimpse of brassiere―Holy shit! That one's dark red!―and counting teddy bears on her underwear visible through light-colored pants. But it's also true I can't tell you when it transformed from the generally forbidden―the same reason six year-old boys try to peek in on their older cousin in the bathroom―to the specifically sexual. Sorting out why a particular aspect stands out to any individual is a difficult task, but also one I encourage both in general and particular. Thus, perhaps your question about an almost sexual thrill is wrongly phrased; one might note Ferenczi's postulated confusion of tongues, in which case the first question becomes whether a thrill derives from the sexual in particular or the forbidden in general. That is to say, perhaps you are observing something genuine, but assigning internalized values to the behaviors instead of considering them according to the fact of other people. That is, perhaps the young girl is tapping some interpretation of sexuality, but is it hers? What if the thrill of the cartwheel is just the risk of being unladylike? Of spreading her legs and maybe someone might possibly be able to glimpse her underwear. Can we be certain it is "sexual", or is it merely the thrill of breaking the rules, which in this case might well be established according to familial standards that happen to include certain foci derived from, say, the parents' sexual outlooks? In the moment she breaks the rules, is it really sexual? That, in the end, seems a presupposition that doesn't necessarily fit.