Popeye being an action man and a strength-based character, his cartoons have oftentimes been observed to be "all about the muscles." Popeye's victories are frequently presaged by him doing a muscle pose, sometimes with a depiction of some element of great potency (a volcano, a stick of dynamite, a nuclear warhead) appearing on his bicep. This powerful symbol of his strength mostly occurs as indicative of his ingestion of spinach which, at least in the animated adaptation, is his ultimate source of dominion over his enemies.
From the time of his creation by Elzie Segar in the late 1920s, Popeye has been characterized as a tough and wiry sailor who never backs down from a fight. He possesses enormous forearms like a stevedore's, made all the more prominent by his very thin upper arms and other body parts. This device serves to underline his deceptively strong nature as well as (most notably in the animated cartoons) to emphasize the transformation wrought by the spinach, in which his upper arms gain oversized muscles, accompanied on occasion by an enlargement of his chest - which has been known to even grow chest hair. The muscle growth is a momentary phenomenon, however; the resultant power surge remains in force until his enemies have been thoroughly beaten.
Although Bluto's portrayal varies, he is frequently drawn to be very muscular to appropriately challenge the combative protagonist. From his inception in the early 1930s Bluto has been a much larger individual than Popeye, with more conventionally scaled arms, legs, and chest. In his Segar and Fleischer incarnations, however, his size was offset by a paunchy girth, leading to the plausibility of the defeat of this lumbering, overweight ox by an agile, vigorous man. Beginning with the cartoon The Anvil Chorus Girl in 1944, Famous Studios brought Bluto's physique more into a bodybuilder mold, with a narrower midsection and a bigger chest. However, the KFS cartoons of the early 1960s brought the bearded bruiser back to his oafish stature, thus turning him into "Brutus".
Several less-animated characters from the comics (Toar, the Goons, Bolo, etc.) and brutes in general are depicted as large and conventionally muscled to appear threatening in contrast to Popeye's incongruously small frame. In a number of cartoons (e.g. Never Kick a Woman, Hill-billing and Cooing), Olive Oyl makes use of Popeye's spinach to acquire the same kind of might to beat other muscular female adversaries. Popeye's nephews have also been known to gain instantaneous muscles by eating spinach and to beat up Bluto and even Popeye himself.