Strong people usually have endurance, and people with good endurance are usually strong. My impression of the basing of armor maxes off Bodyx2 has always been that it's not a case of "can you lift 30 pounds easily," it's a case of "can you carry 30 pounds for 8 hours and not care?"

Basing it off Str + Body seems just as good of a way of judging overall physical condition.