Polykleitos, Doryphoros, Roman marble copy of a 5th century bronze, Archaeological Museum of Naples

Like most of the free-standing sculptures that remain from the classical world, what we have handed down to us are Roman marble copies of Greek bronze originals.  The  Doryphorous is no exception.  Sometimes called the "Canon," in the ancient world as now, he was sometimes taken as the most authoritative expression of the human ideal from classical Athens. ("Canon" refers to an exemplary standard, as in the "canonical books of the Bible", or the "canon of English literature").

"Classical," in this and the most basic sense refers to fifth century BCE Greece. He has all the features that came to be thought of human perfection: He's, well, male. He's publicly nude, as an athlete would be at the time and uncircumcised, with an athletic and youthful (as opposed to more mature, more massive) body.  His stance is weight-shifted, what art historians and artists call, in deference to typically Italian nomenclature, "contrapposto"--counter-posture. He shifts his weight onto his right foot, rextending his left leg, which throws his body into a relaxed "S" curve (in this view a backwards "S") in a sinuous line from his slightly turned head through the midline of his torso, tipped hips, and out his left leg.

"Doryphoros" means "spear-bearer": his left hand originally held a bronze spear.  The spear, and the Greek bronze sculpture by Polykleitos, is lost; bronze was frequently seized to be melted down for weapons or vessels.  Purely utilitarian and opportunistic "re-purposing." The post bracing his wrist from his hip, and the truncated stump supporting his leg were necessary in free-standing marble sculptures as they would not have been in bronze.  When you stop to think about it, the standing human body--the represented nude human body, that is--is supported by its thinnest part in the vertical line from the head to the feet, the ankles.  The whole mass of the body tips on that narrow base.  It's not a good  engineering plan, especially for marble with its high compressive strength but low tensile (flexible) strength--the opposite of bronze.  This is of course why the small, narrow projections are frequently broken off from ancient sculpture--noses, feet, hands, penises--even heads at the neck and whole bodies at the ankles.

While he's fit, he's not "cut" in the modern sense.  His body's planes are articulated in relatively simple, continuous, horizontal lines: from his arm pits under his pectorals, from his inguinal muscles (very important to the ancient world's conception of male body structure) to his groin, and across his knees. Mostly his body is smooth rounded shapes and clear, continuous outline, except for those three horizontal divisions.