"se ttu apri tanto le gambe che ttu cali da capo 1/14 di tua alteza, e apri e alza le bracia che colle lunghe dita tu tochi la linia della sommita' del capo, sappi che'l cientro delle stremita' delle aperte membra fia il bellico, e llo spazio che ssi truova infra lle gambe fia triangolo equilatero"
"If you open your legs so that you shorten from the head 1/14 of your height, and spread and raise the arms till with the long fingers you touch the line of the top of the head, know that the center of the ends of the spread limbs is the navel, and the space between your legs is an equilateral triangle"
Here is an add on to the Vitruvius details, calligraphic by Leonardo Da Vinci at the top of the drawing; on a circular projection which presupposes, alas, that the arms stretch out more whilst the legs are shortened, the same ones that have determined the square with reliable theoretical precision.
As we can see, the spread legs in the drawing do not reach the equilateral triangulation with the navel; therefore, any other triangle as such, resulting from the legs positions, is casual and out of symmetry, hence meaningless. 
Note that, should the legs widen enough to really form that triangle, the forced reduction of distance of the [dark shaded] foot from the correct [red/yellow] arc would be maximum, being on the same sides of the triangle [green], which align the heads of the femurs to the navel, i.e. their radius with the center; but the figure could have been less pleasant.
It should be noted alike that this alignment does not mean that the rotation of the legs is centered on the navel, what could justify the original design; as well as the rotation of the arms is not centered on the crossing of the line of the shoulders with the sternum; which is not responsibly applicable (more details later), even if suggested offhand by the original drawing.
Definitely, the rotations of the limbs have their anatomic trajectories, which cannot be passed over.
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